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Discussion Starter #1 (Edited)
Most of you agree there are THOUSANDS of some type of "jetting questions" on the Org....

and I have spent my share of time trying to answer many of them....

So, what I purpose, is a PINNED thread, which will allow most people to understand jetting, determine jetting needs, view what the most 'common' jetting is and/or questions, and if all else fails, give proper guidelines as to the INFORMATION (including proper terminology) needed for us members to post ACCURATE jetting information for those who need answers..... lets hope this works... lol

Lets start with the basic/stock jetting: Before we begin, at this point in time, there are basically TWO different machines when it comes to jetting. The stock 04/05 machine which utilizes a 42mm Keihin butterfly/slide carb, and the 06/newer machines which utilize a 40mm FCR (Flat CR style carb). Let me also say the 04/05 machines suffered from a bit of a 'restrictive' style intake and filter... while the 06/newer machines work very well with their factory intake and filter. Hence the reason for the massive changes in jetting between all corked up (stock) and uncorked (lid removed or modded) between these years.

04/05 came with 118 main jet, #48 slow jet (aka Pilot jet) and an adjustable needle. There is no removable Leak Jet (aka Acc bypass jet). the FUEL SCREW (aka Pilot Screw.....NOT Air-Fuel or Air screw or A/F screw) should be set near 2 turns out to begin...

04/05 HRC jetting is 185 main jet, stock slow jet, special 'opened up' HRC style LID. thats about it....

06/newer came with 120 main jet, #42 slow jet, non-adjustable NHHU needle, 2 3/8 turns out on Fuel Screw, #70 leak jet...ignore the #75 starter jet...

06/newer HRC jetting is 162 main jet, stock slow jet, NGPR needle on 3rd groove from top (all adjustments on needle are considered from the TOP and/or ROUND (not pointed) portion of the needle), #55 leak jet, turn fuel screw 1/2 turn IN from stock (1 7/8 from seated position) and turn acc timing screw (1/2 turn OUT from stock) both of these screws are a special 'D' shaped head, so you need the appropriate tools and/or modifications to these screws (such as cutting a slot in them) in order to adjust them....this requires the LID to be REMOVED or highly modded.

Ok....lets start with some basics:

from Idle or starting to WOT application. Idle jetting is controlled with Slow jet and Fuel screw, along with the choke mechanism (most know what the choke is for so I will skip the details)....common rule is to adjust your idle setting (not speed, which is adjusted with the black idle speed knob) first using the fuel screw. open screw up to about 3-4 turns out and begin turning this screw IN/CLOCKWISE slowly while listening to the RPM of the engine. once MAX rpm is obtained, back this screw out about 1/4 turn (based solely on my experiences). This is usually about as close as your gonna get depending on other issues. If you find the Fuel screw at less than ONE turn out from lightly seated position (go with next size SMALLER slow jet), and if out more than THREE turns, go with next size LARGER main jet. Then start this procedure over until the fuel jet is adjusted correctly, and it falls between 1 and 3 turns out from seated. this adjustment is usually performed in the garage.

Off idle and/or Mid range adjustments can best be handled by the Needle, but since all of the carb circuits tend to overlap, the fuel screw, slow jet, and main jet, will have a small effect on this. both the needle taper (so choose your needle wisely) and needle 'clip position' alter this jetting. Take the bike out for a decent NO LOAD, CRUISE speed at about 1/2 throttle (steady), 4th gear. Listen for POPPING/SAGGING/CHOKING.... not an easy task unless you know what to listen for. If she tends to Pop Pop Pop or you feel the engine SAG off, then pick up again, then SAG off again (like Lunging forward/back)... your probably LEAN, and you need to Raise the needle by LOWERING the clip position. If you feel your bike coughing/spitting, she is probably FAT and you need to LOWER the needle by RAISING the clip position (when giving or reading tuning advise, be very careful to note whether you want to RAISE/LOWER the NEEDLE, or RAISE/LOWER the CLIP, cuzz they have the opposite effect. Most people refer to raising/lowering the NEEDLE, info only.

WOT and/or MAIN circuit. Easy enough to fix, simply change the main jet. The difficult task is knowing which way to go, and how far to go. Same as with adjusting the needle, except running at WOT, preferably under a load, for as long as you can. Try and get a sense for what a lean condition feels like vs a rich condition. If the bike is VERY LEAN, she will sag a bit and 'lunge' a bit but she will sound very 'clean' if you know what I mean. If the bike is VERY RICH, it probably wont ever 'clean' out, and you will hear/feel a coughing/spitting sound, not to mention she wont want to reach max RPM. Go smaller number on the main jet to LEAN her down or go larger number to RICHEN her up.... another method is the plug cut, but this can become costly if using the stock Iridium tipped $20 plug. A cheap alternative is a typical $3 NGK BR8S or similar suitable plug JUST for this test. Put in NEW plug, take bike out for a short trail ride to put a LITTLE color on the plug, then proceed with WOT for as long as you can hold it. Do not allow bike to decelerate or idle, simply hit the kill switch and let coast to a stop. Remove plug, cut away the threads and look at the inner porcelain area. This is where you coloration comes from. you want a TAN or LIGHT BROWN color. darker = too rich, and lighter = too lean. Blisters on the plug indicate WAY TOO LEAN and/or detonation issues. Soot or thick black carbon usually indicate your burning some oil... typical for a high mileage machine with old plugs... last but not least is the Dyno... probably the very BEST method w/o a doubt, but it is costly, time consuming, and not all dyno operators are created equal....I would prefer having an Air/Fuel meter on the dyno, but again, I know not to RELY on this meter for tuning my machine. It should be used as a REFERENCE once your machine is TUNED, in order to have a set goal for the NEXT TIME you need some adjustments.... the reason being is simple, this is not one PERFECT A/F ratio for each machine, and it certainly is not anywhere near the 13:1 standard line they have on their graphs (at least not in my humble opinion). So use the dyno for what it can do best, measure HP and TQ. run your machine to WOT and adjust your main jet to obtain MAX HP and TQ, simple. then, once all said and done, note the A/F ratio on the graph so you can match that number next time you need a tune up or have made some major changes to your machine. This issue with most, not ALL, dyno operators is that they are really in business to make money, and there is NOTHING wrong with that.... but, as you know, TIME is $$$. And even though I wanna believe that most must know the proper method for tuning a machine, they simple take short cuts in order to get you in and out of their shop. There are however some excellent dyno tuners that will spend as much time you like to dial your bike in, and they are well worth the money.... One item to mention when dyno tuning is this. RPM does not = CARB POSTION.... and this is where so many dyno tuners fail. For those who have put your machine on a dyno, how long did the bike run once the operator started this operation? 2-3 seconds? max. There is no way you can adjust your idle/pilot or mid range circuits with this type of dyno "pull". Even though the graph/rpm will start out at 1000rpm (or so) then travel up to 10,000+rpm, the throttle position was put at WOT. This is simply how a dyno pull is done. Do NOT confuse the 2000-3000 rpm range on the graph as the Pilot Circuit, and do NOT confuse the 5-7000rpm range as MID RANGE. Cuzz they are not, the entire "pull" was done at WOT, and the only circuit being utilized by your bike was the MAIN CIRCUIT... the rest was just playing 'catch up'. So, if your gonna perform a dyno tune, do it correctly, and you will be very pleased. Let your bike run on the dyno with almost no load, idle to 1500 rpm, and adjust the pilot circuit accordingly. then bring her up to about 5-6000rpm, and adjust your mid range (needle) accordingly. Then, last but not least, WOT, and adjust your main jet for MAX hp/tq.... DONE, and your bike is now fully dyno tuned.....

Now, lets start with some of the ISSUES associated with tuning... and the most common is the dreadful BOG/BAWG associated with the typical 4-stroke machine. Unfortunately for you 04/05 guys, there is no 'direct' fix for this on your carb, so you have to steal from Peter to give to Paul so to speak.... if the bike does in fact BOG (while riding, NOT IN NEUTRAL), then you probably need to increase fuel into this circuit. Raising the needle is the most common for 2-strokes (which have no acc pump circuit), next comes increasing the pilot circuit fuel by going with next larger Slow Jet and/or a combination of both. For the FCR guys, you can simply alter the leak jet. Smaller jet = MORE FUEL (the leak jet is a 'bypass jet' meaning when you depress the throttle, the plunger in the acc pump forces fuel out of the float bowl (plunger bowl area) and into the venturi of the carb, however, there is a 2nd path the fuel can take, and that is to BYPASS the venturi and be squirted back into the float bowl via the leak jet. So, the smaller the leak jet, the less fuel can be 'bypassed' and more fuel gets dumped inside the venturi. Stock was #70, HRC is #55, some go down to #30-35, but I do not recommend soldering this jet shut or going with a plug. This jet serves two purposes... allows for an ADJUSTMENT for the acc pump not found on the older 42keihin carb, but it also allows a release in pressure inside the acc pump diaphragm in order to reduce any DAMAGE that can occur. Remember, fuel/liquids do not compress easily, so you can easily rupture a diaphragm disc if depressing the throttle too quickly and not allowing for some of this pressure to ESCAPE via the leak jet (info only).... another aspect of this 'bog' issue is the acc pump TIMING.... Many people have cured this headache simply by turning the timing screw out 1 1/8 turn as recommended by HRC... Also, if you find your down to #30 or #35 leak jet, and you still have a dreadful BOG when accelerating, you can also raise your needle or increase your pilot circuit fuel. This is not a 'direct' fix, and yes, it does cause these circuits to be a bit RICHER and required, but it will help to reduce a bog if you cant cure this bog via the leak jet alone. the 04/05 can benefit from aftermarket pump covers such as Boyseen. These covers over a larger 'bowl' of fuel so more fuel can be squirted into the venturi. They are certainly not needed on the FCR carbs in MY opinion.

Lets talk about "popping on decel".... a quite common term heard often on the Org. Popping on Decel is caused by a LEAN condition inside the combustion chamber while the butterfly/slide is in the closed position. It can often be 'cured' by increasing fuel in the pilot circuit (1/2 turn out on fuel screw or next size larger pilot). The issue is that this is not the proper procedure for tuning your machine and it is more like putting a band-aid on an injury than actually fixing the problem at hand (if there is a problem). Commonly, you will notice this effect when changing your exhaust. A less restrictive exhaust allows a larger volume of cool air to be 'sucked' backwards via the exhaust pipe and into the combustion chamber past the exhaust valves. The REASON for this on Decel is simple. Your engine is still turning at a rather HIGH RPM, yet the carb slide/butterfly is CLOSED. Since the opening and closing of the valves is a mechanical one (via timing chain/gears/cam/etc), you cannot just STOP the engine from wanting to SUCK air into the combustion chamber. So, since it can no longer SUCK enough air thru the carb because it is closed, this excessive 'vacuum' tries to suck air from wherever it can....and yep, the exhaust is the next logical target. So although any small leak in the crush gasket would go unnoticed during normal operation, during DECEL it becomes quite prevalent. This cool/incoming air causes the lean condition and hence, POPPING. There is absolutely nothing wrong with your jetting, so if you begin enriching your pilot circuit, your jetting will now be richer than required during normal use. Sometimes a failing header crush gasket is to blame for allowing air to enter the system and a simple replacement can cure the popping. If however, this popping is a result of a new pipe system, and all components are sealed, you only have two choices. One, you increase the jetting in the pilot circuit as mentioned to help combat this issue, or, you do nothing, and live with the fact that this is a COMMON phenomenon and in NO way alters your jetting. The choice is yours. If you have a hard time believing this can be 'normal' and/or 'properly jetted', just watch some good ole NASCAR races. You can easily view the popping and/or FLAMES shooting out the tail pipes (side pipes) of these machines as they begin to enter the corners, then it disappears during the exit of the corners because the driver applied his throttle. Some of the cars will have flames, some will just pop, and yet others will do nothing. Trust me, each of those vehicles is tuned by EXPERTS in the performance industry and you could not tune them any better. bottom line...some mechanics leave the tuning alone and let the cars POP on DECEL, and others might want to eliminate the popping and add a lil extra fuel in the pilot circuit because this popping CAN cause issues with the exhaust valves (I really dont know their individual reasons, I am just speculating based on my experiences) Not very common nowadays, but old school days you could 'crystallize' a valve if running un-corked headers on a track that required the use of DECELERATION to slow ya down. Never an issue at the drag strip however....lol

Next, lets talk about proper jetting and why so so so many people continue to go with larger and larger jets, yet never smaller. If any of you have read some of my posts, your probably familiar with MY opinion on jetting, which is this: WAY WAY WAY TOO MANY PEOPLE believe MORE FUEL is BETTER. This includes major performance companies and tuners alike. The reason is simple. Most people have the 'belief' that if you "need" more fuel, then you have somehow increased the performance of the machine. And, to be honest with ya, that is quite true. What most people do not identify with is that JETTING has LITTLE to do with the 'amount' of FUEL, and most specifically, the fuel REQUIREMENTS, UNLESS your jetting the exact same machine, with no changes to the engine, intake, pipe, volumetric efficiency, etc.....if everything ELSE remains the same, then increasing or decreasing the jet sizes will alter the Air to Fuel ratio:

But, here are some "myths" if you will. "I just bought a new brand X pipe, and they recommend larger main jet and slow jet"....conclusion: this new pipe flows MORE, therefore requires larger JETS, therefore making more HP. WRONG!!!. again, JETTING has very little to do with fuel REQUIREMENTS. The manufacturer of this pipe had to make a decision. They could either be honest and lose money, or be deceitful and make money, Ill let you guess which. Because the overwhelming MAJORITY of customers honestly believe that by needing a larger jet they are making more power, the manufacturer had almost no choice, but to recommend larger jets. And since this 'free flowing' exhaust is more than likely going to cause some type of 'popping on decel', they again had no choice but to recommend larger jets for the pilot circuit, simply to reduce the number of COMPLAINTS or QUESTIONS coming into their company....both of which are 'wrong' but allowable....

Let me start over with this bit of information... as an engine becomes more EFFICIENT, specifically the volumetric efficiency (identified with the symbol Ve in the industry) the need for larger jets becomes less. Now remember, and here is the TRICK (if you will) to jetting but remember the difference between needing larger JETS and needing more FUEL. The actual Air to Fuel ratio has remained the same, but because whatever MODS were done to the machine, the air flow into the carburetor has become LESS, and therefore, by simple physics, you must increase the jetting in order to maintain the SAME A/F ratio. This is the KEY to all the BS behind jetting. If you increase the bore or stroke or Ve (by porting usually: Ill discuss CAMS in a minute) or have a BETTER (not MORE) flowing exhaust, etc....then you have just increased the Ve of the engine. This means there will be a larger influx of air through the carb. As the AMOUNT/VOLUME of air increases, using the exact same carb diamter, then in order for this larger VOLUME of air to pass through the venturi of the carb, it must INCREASE IN VELOCITY to do so. Think of a river as it cuts a path down the mountain. As the area where the river widens, the flow slows down, but as the river reaches a NARROW path, the same VOLUME of water wants to continue flowing, so the SPEED of the river must increase as it narrows. Ok, back to this carb, as the air increases in velocity, the ability of this increased incoming air to SUCK fuel UP from the float bowl becomes GREATER. Ok, lets stop for a second and talk about the effect of an airfoil (wing). as air travels over an airfoil it splits and becomes separated. the air traveling over the top of the wing wants to meet up with the same air traveling over the bottom of the wing. the airfoil is designed in such a manner (in MOST occasions) so that the air particles traveling over the top of the airfoil must travel a longer DISTANCE than those traveling over the bottom (FLAT on high lift aircraft). So the air traveling over the top must INCREASE IN SPEED in order to reach the end of the airfoil and keep in line with the bottom air. This increase in speed causes a lower pressure on the top of the wing than on the bottom. It is this DIFFERENCE IN PRESSURE that causes lift. The venturi of the carb is no different. It is shaped in such a way so that incoming air must INCREASE in speed when traveling through the smallest portion of the carb (Venturi/Center). As this air increases in speed it looses PRESSURE, so that the rather stagnant air inside the float bowl can push the fuel UPWARDS towards this low pressure area inside the venturi (consider typical atmospheric pressure at sea level is close to 14.7psi) (and trust me, Barometric pressure, weather changes, temperature, altitude, etc, play a HUGE role in jetting...and im actually kinda knowledgeable in this realm, but that would require another 10 pages of typing..sorry...lol)....so, I will often use the term SUCK and/or DRAW fuel into the carb, but in reality, and if you remember this for the rest of your days, you will have a much CLEARER picture of how to make HP (specifically in the intake area) but fuel is not SUCKED from the carb, nor is air SUCKED into the filter/intake/engine...buth rather it is PUSHED into the filter/engine/venturi by atmospheric pressure inside the float bowl (what this means is if you have a clogged float bowl vent, your gonna run VERY VERY LEAN) (also, if your float level is LOW or HIGH, this will effect the ability of the fuel to be PUSHED upward into the venturi) (and dont even get me started with pressurized intakes such as PRE-CARB nitrous or TURBOS, cuzz they become a PITA). SOOO, if you actually INCREASE the Ve of your engine, although your Air to Fuel RATIOS become the SAME, you have increased the ABILITY for fuel to enter the venturi via a lower pressure inside the venturi. This means you must REDUCE your jetting, not increase it.... now a pipe manufacture may claim you need more fuel, but if they built the pipe correctly, that would be doubtful at WOT applications. However, they can easily recommend a larger pilot jet based on the fact their pipe probably POPS a lot more on decel and they simply are trying to correct this 'issue' without a lot of complaints and/or phone calls..... larger bores and longer strokes tend to increase the incoming air and therefore require smaller jets. Porting SHOULD do this, but not all porting is equal, so it is difficult to recommend jetting not to mention if you port for max HP, you will probably need a smaller main jet, but more than likely larger jets in the pilot circuit, cuzz that is simply the nature of the beast (you either get better low end, mid range, or top end). This brings me to bumpsticks. Chances are if you using a top end oriented cam, this cam will produce the best results in the upper rpms (more flow) but at lower rpms, you will actually have LESS FLOW, so at lower rpms, you will probably need to increase your pilot circuit fuel requirements to compensate, while your top end fuel requirements (actually jet sizes) will become less... remember, all bumpsticks are different and I would never presume to know how to tune them all, just giving out some BASIC tuning guidelines...

My point is this... rarely does anyone suggest LEANER jetting when modding these machines.... quite the opposite, too many give out suggestions indicating the need for larger and larger jets... and in MY humble opinion, falsely so. Remember, HRC gives you a #162 main jet and actually require you to turn your fuel screw IN (leaner) 1/2 turn with their jetting. and Honda still warranties this product. So if they were way too lean on their suggestions, dont ya think Honda have issues with this warranty? Trust me, if anything, Honda recommended slightly RICHER jetting than optimum. So if your at sea level, cool ambient air, high pressure system, etc... your probably fine with this jetting. BUT, if your above 1000 foot level, hot humid climate, low pressure system, etc.... you probably need LEANER jetting to be optimum.... they "myth" that lean jetting will blow up your machine vs rich jetting is just that...a MYTH (it CAN happen, but requires a certain set of circumstances including LONG/WOT application for the most part)...How many times have you read on the ORG where a guy removed the lid (cuzz he read that somewhere) and never changed the jetting. Yet the only complaint was poor performance. and that is a HUGE lean jetting issue, not just a few jet sizes..... now 2-strokes are a bit different, we are only discussing 4-bangers and specifically the 450R for now.....

a few facts: Cooler air is more dense and requires richer jetting: Higher Elevation is less dense and requires leaner jetting: Dynajets work just fine, but have a different numbering system, so make sure you know what your comparing them to when reading jetting information. My information is based solely on factory Keihin jets.

Ok...lets talk about information needed for accurate jetting. If you have to ask about jetting, please include the year machine, any carb mods, your intake system, filter type, (stock vs intake eliminator type) whether lid is ON or OFF or MODDED (very important) pipe mods, bore/stroke, cam, ELEVATION and ambient air temps, etc.... this information is very helpful when trying to determine proper jetting.... dont just say modded lid, we need to know how was the lid modded (size and number of holes, etc)... hint: if your gonna mod the lid, make sure you cut large enough holes so as to not have any RESTRICTIONS when using the lid. a couple of small 1" holes will only confuse the jetting issue, because it will flow enough in the pilot/mid range circuits, but will be restrictive at WOT, so the jetting will be off....also, if you complaining of a BOG, indicate whether this is during riding or sitting in the garage blurping the throttle.... and last but not least, make sure all other mechanical/electrical issues have been fixed/evaluated. I cant tell you how many electrical/stator/ICM issues can act just like JETTING. OH...do not use the term "I have a stage II jet kit"...not even if you know the brand "sparks vs FMF vs Dyna, etc". We need to know the actual BRAND of JETS and their SIZES.... Keihin vs Dyna vs Mikuni, etc....

Now let me say this... I am NOT the tuning expert on the Org or anywhere else for that matter.... there are literally hundreds of much higher qualified tuners than myself on here. I am only giving you information based on a long time enthusiasm for building/tuning/racing a wide variety of machines. So, with that being said, you will not STEP ON MY TOES if you disagree with me. Any information is welcome.....

If you have any questions or information you think could be useful, please ask....ill do my best to answer them and make it a part of this pinned thread.... Thanx

And I apologize for the length of this thread, sometimes I just dont know when to STFU....

JMHO...Greg
 

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Lots of good info Greg. :thumbup:
Thanx for taking the time to explain it all.

Only thing I can add would be to jet the main first, then work way down to needle and then the pilot jet.
This will ensure more accurate jetting and reduce your jetting time.
 

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Great job on the write up as most who give advice including myself simply tell someone you need jet #xxx for the main and so on so people do not know why or what determines they need this jet and just install it and ride but now people can actually understand what the meaning is for jetting recommendations and how to determine what they really need to do to tune their bike for optimum performance again great job and thanks for the info as I learned alot and I am sure others who take the time to read will as well
 

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Discussion Starter #4
Zips, I havnt noticed any difference between starting points, but if you have, more power to us all..... so if you want, start with main jet and work your way down....good info...

and dont forget... most jetting circuits OVERLAP those next to them... so when/if you make changes to one jet, it CAN effect others, such as raising the needle, will probably also fatten up the Pilot Circuit, along with the mid range, and it "CAN" effect WOT, even though the needle is raised up out of the main jet area, if your running a FAT needle, it can still restrict the flow of fuel up from the main to the venturi.... so you kinda have to work back/forth with jetting at times.... it really all depends on how large of steps your taking....

im gonna let this thread run in the engine section to obtain as much info as we can, before PINNING this thread.

thanx for the input guys....g
 

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Excellent info, thanks for sharing. As with anything else in the "I read it on the internet, so it has to have some merit" files, it is going to be difficult for people to dial in their rides, given different elevation, air quality, etc... so I thought it may not be a bad idea for members to post their tune ups, mods, and areas that they ride in(elevation-wise). I don't have access to a dyno, so I continually drag race with my riding buddies as I make changes and compare results. I have been battling some tuning issues and have them mostly sorted out, but I am still trying different things to maximize performance and driveability, if you will. I have definitely come to the realization that these 4-strokes run best "on the verge of being too lean". I say this with a nod to 450RRR's post about "more fuel isn't always better".
Mine is an '05 450r, so this really only pertains to '04-'05 models.
My first mod was a switch to a K&N filter/outerwear, K&N powerlid w/outerwear. K&N's instructions say to raise the needle(4th clip setting), and they provided a 165 and 170 jet. BACK TO THIS PART IN A MINUTE! Still ran good since I uncorked the intake side, but my main jetting seemed too lean. I was all over the board, going up to as high as 200 jet, and finally settling on a 190 jet. It seemed to pull on top best while racing my buddies quad, so I stayed with it. Mind you I experimented with some exhaust changes(MY MISTAKE-TOO MANY CHANGES AT ONCE), removed my stock header and white bros. E2 slip on, tried the stepped header and bill ballance muffler, which killed all the bottom end BTW. Long story short-I was changing too many things. Enter another riding friend with an '04, all stock with an FMF powerbomb header and bill ballance muffler, drilled holes in air lid and a uni filter. And his had all the torque down low with a hard charging top end. He bought it as-is, and-lucky S.O.B. has it running great. So after conversing with some other riding buddies(and going back to the K&N instructions) that even guys with no lid in my area aren't running that rich-needle on 3rd clip position, lower main jetting, etc..). I think maybe K&N was just covering their ass by making sure it would be too rich than too lean.

So I changed my tune to my buddies '04 and whereas before he was top-ending me, we are dead even now. (SIDE NOTE: after riding his, I loved that FMF powerbomb, and the fact it didn't lose any bottom end and had added great pull on the top-I had to get it, money well spent IMO). She's running as strong as ever now, so I'm going to put my tune up and mods here, and maybe it would be a good idea for others that have their ride dialed in with their local riding elevation, tune up, modifications, etc... as EVERYONE in different riding areas will have different tune ups.

'05 450r stock internals
Riding elevation in my area, approx. 800ft. above sea level, approx 1000 ft at little sahara, OK.
K&N filter and powerlid, both w/outerwears
FMF powerbomb header
white bros. E2 slip on(which fit the pipe great after some minor expanding of muffler inlet)
NOTE: it's just my personal opinion that there are a bunch of WAY TOO LOUD mufflers out there, so it was my attempt at making power and still keeping a reasonable decibel level as to not annoy local anti-atv folks(this muffler is touted as being the quietest muffler around at that time I purchased it).
185 main jet(stock-118)
needle back to stock(3rd clip) position
50 pilot jet(stock-48)
pilot screw at 2 turns out

I have some more testing to do, as I have found the outerwears need to be cleaned WAY more often than I realized-DUH-, so after servicing all filters, outerwears, I'm going to do a thorough(as possible) test on filters, and lids. I'm checking the stock foam filter vs a uni foam filter vs the K&N, and the K&N powerlid vs HRC lid. I know the best results will be found on a dyno, but since I don't have access to one I'll have to use what I have, and drag racing is just too damn fun anyway.

Sorry for the long rant, but just thought I'd share my experience in getting the most out of my stock(internals) 450r.
 

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lots of good info, but man that hurts my eyes to try and read it all. lol
 

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Nice write up. Got a quick question. I adjusted the fuel screw and then the idle so it runs perfect and drops down to 1700 RPM's almost all the time when it is idling. BUT when I put my HMF quiet core in when I ride at the National forest (99 db's or less ugghh!!) it has a very hard time idling. Sometimes it will drop to around 1500 RPM's and sometimes it will jump up to around 2000 RPM's. There is not a lot of elevation change. I think the cause it that since the quiet core bottles up the exhaust, it is running rich at idle. Shoud I perform the idle adjustment procedure again when I put the quiet core in and then when I take it out? Thanks for the help. I have an adjustable fuel screw so it would be really easy to do.
 

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Heres my info
2007 450ER
Stock Motor
HMF slip-on
UNI filter
EHS racing lid
162 Main
3rd clip NGPR needle
Stock 42 pilot
55 leak jet
fuel screw 1 3/8 turns out
Runs PERFECT when moving, idles great, starts great, only thing I am not totally happy with is when in neutral and crack the throttle open real fast it just dies, still not sure on why but as 450rrr said before if the bike runs great when your riding it then thats all that matters.

Also Im at about 1000ft elev., and pretty hot and humid here in Iowa
 

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I'm sure getting tired of all these jetting questions.
Sure hopes this helps, good thread...... :thumbsup:
 

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Heres my info
2007 450ER
Stock Motor
HMF slip-on
UNI filter
EHS racing lid
162 Main
3rd clip NGPR needle
Stock 42 pilot
55 leak jet
fuel screw 1 3/8 turns out
Runs PERFECT when moving, idles great, starts great, only thing I am not totally happy with is when in neutral and crack the throttle open real fast it just dies, still not sure on why but as 450rrr said before if the bike runs great when your riding it then thats all that matters.

Also Im at about 1000ft elev., and pretty hot and humid here in Iowa[/b]
Thanks. I am running with the air box lid off a 165 main and a 48 pilot(thats what HMF recommended) and it works great. When I crack the throttle open real quick, it doesn't die so maybe a slightly larger pilot might help. I would think the smaller leak would have helped that but I guess not.
 

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Discussion Starter #13
Nice write up. Got a quick question. I adjusted the fuel screw and then the idle so it runs perfect and drops down to 1700 RPM's almost all the time when it is idling. BUT when I put my HMF quiet core in when I ride at the National forest (99 db's or less ugghh!!) it has a very hard time idling. Sometimes it will drop to around 1500 RPM's and sometimes it will jump up to around 2000 RPM's. There is not a lot of elevation change. I think the cause it that since the quiet core bottles up the exhaust, it is running rich at idle. Shoud I perform the idle adjustment procedure again when I put the quiet core in and then when I take it out? Thanks for the help. I have an adjustable fuel screw so it would be really easy to do.[/b]

I would imagine a quick adjustment of the fuel screw would cure this issue... as for which way to go, I could not say... but most 'stock' or 'quiet core' type mufflers are actually gonna be a bit rich if comparing them to a more open type exhaust like dasa or ESR..... and the reason is quite simple... the restircitive muffler actually produces better performance DOWN LOW (usually).... it makes a more effective 'Ve' engine at low/mid operation.... so since it is more effective, it has increased the flow of air through the carb and is actually capable of sucking MORE fuel rather than less.... so go about 1/2 turn at first... if that doesnt work, try the opposite direction.... dont forget to DOCUMENT what pipe likes what setting... so next time you switch back and forth, you know exactly where to go with it....



More info: since I kinda got tired of typing and lost my train of thought several times... as you can tell by the random babble.... lets talk about the carb components and their respective NAMES..

starting at the bottom and working our way up....

you have a FUEL screw on 99.9% of 4-stroke carbs... it can easily be identified by WHERE on the carb it is placed.... if placed at the rear of the carb...(near the head)...its a FUEL screw... if placed on the intake of the carb (air filter side)... its an AIR screw (typical on 2-stroke machines) some people call this an A/F screw (kinda correct as it adjusts the Air/Fuel mix, but so does every other component of the carb) also known as the PILOT SCREW.....since it is part of the pilot circuit...bottom line... it will be some type of ADJUSTABLE 'SCREW'

next comes the SLOW JET...also known as the Pilot JET, again, because it is part of the Pilot Circuit... it works in conjunction with the fuel screw...... this is a removable/replaceable style JET.

also, as a member of the Pilot Circuit, the SLOW AIR BLEED needs considerable consideration considering (you like how I used the same word three times in a row and in a grammatically correct sentence? lol) how important the role of the slow air bleed is.... as relevant by the name...this is a jet (usually located in the carb bell (or entrance) and is used to allow incoming air to EMULSIFY (an important aspect for proper jetting and more importantly yet... PERFORMANCE). The incoming air mixes with the fuel in the pilot circuit BEFORE it can enter into the carb venturi and ATOMIZE (another very important function of the carb and specifically, the air bleeds). The slow air bleed allows for a more proper TUNING, better ATOMIZATION, and a type of 'give or take' effect allowing for a less FINICKY (word) carb.....some have removable air bleed jets (the FCR uses a Keihin #100 air bleed) others are a fixed hole.

next is the NEEDLE... more complex than one would think.... and an important component to know correctly as it can be very confusing.... first is the JET NEEDLE (commonly referred to as the NEEDLE).... sometimes fixed and sometimes adjustable by numerous slots on the head of the needle (soft/round portion vs the tip: sharp end)... all adjustments on an adjustable needle are considered from the TOP... in other words.. if someone says put the clip in the 3rd position.. that is 3 clip positions DOWN from the HEAD/LARGE end of the needle)... needles come in various sizes/tapers, etc... and can only be adjusted in height.... raising the needle by LOWERING the clip position increases fuel and vice-versa... but, it does not just initially increase fuel like a larger jet... .what it actually does, is allow the main jet to come into play SOONER vs LATER in the throttle position.... so it can help cure a BOG when stabbing the throttle if you dont have an adjustable leak jet or other ACC pump adjustment.... the JET NEEDLE rides inside of the NEEDLE JET... .hence the reason why I said it was confusing.... the actual housing that the needle sets in to, along with the main jet, is called the NEEDLE JET.... most people never refer to this item and it is rarely altered.... but, you now know the difference in case someone ever does mention the two in the same sentence....

Main circuit... comprised of mostly the Main Jet... a removable/replaceable JET, but as mentioned above... the 'needle jet' and the 'needle' itself can play a role in effecting the main circuit...along with another tuning aspect and very IMPORTANT component is the MAIN AIR BLEED... this is the EASIEST of all the circuits to tune... simply run your bike at WOT application (preferably under a load but at upper rpms) and either listen or feel the needs of the engine... or perform a plug cut.. or better yet....dyno tune.... this circuit is rarely confused. The main air bleed performs in similar fashion as the slow air bleed. It helps to allow incoming air to EMULSIFY with the fuel BEFORE it reaches the venturi.... this helps to atomize the fuel which improves the ATOMIZATION effect and therefore, increase performance.

When it comes to air bleeds, the easiest analogy I have is drinking out of cup using a straw.... think of the straw as the needle jet and the cup as the float bowl... the lower the fluid level, the further the fluid must flow before it can reach the top, the higher the fluid level, the closer it becomes to OVER FLOWING.... so fuel level is important, but enough about that.. lets get back to the air bleeds... poke a small hole in the side of the straw above the fluid level... and drink from the straw. what you will find is it becomes MORE DIFFICULT to draw the fluid up from the cup because of this hole....if you put your finger over the hole, sucking the fluid up becomes much easier again... this is the effect the air bleed has on the system... but think about the correlation between how much SUCTION is required vs how much FLUID is drawn up w/o the hole... basically, w/o any type of air bleed (hole in straw) it becomes a 1 to 1 ratio.... you suck X amount, and X amount of fluid will rise to the top.... this is nice when/if you ever need MAX FUEL... but for the most part.. this would make tuning a complete PITA because of the changes in the engine that increase and decrease suction and/or (difference of pressure)... with the hole in the straw, you can suck and suck (no jokes) and yes, you will get more fluid the more you draw on the straw...but not in a 1 to 1 ratio....this helps the engine to kinda 'self regulate' the fuel ratio by not allowing TOO MUCH FUEL to be drawn up the needle jet. Also, you will notice if you drink from a straw with a hole in it...you not only get some of the fluid, but also a large amount of AIR... this air is what helps to emulsify/atomize the fuel for a more proper burn. Again, an IMPORTANT aspect of a carburetor....... if you alter the air bleeds of the carb, you alter how EASILY/READILY the engine can draw fuel from the float bowl... the smaller the air bleed, the more fuel she can draw but with less atomization. The larger the air bleed, the less fuel she can draw, but with better atomization. When would this effect YOUR carb... easy.. when you BORE THE CARB or when you INCREASE THE Ve of the engine (big bore/stroke high comp piston, porting ,etc) As you bore the carb bigger, you make it more difficult for fuel to be drawn up from the float bowl because you have opened up the venturi, and thus, reduces the VELOCITY of air into the carb... (remember back to the river analogy)... the slower the velocity of the incoming air, the less pressure difference is created and that atmospheric pressure inside the bowl cannot force as much fuel up the jet needle..... so, when/if you bore you carb to a larger size... the NEED to reduce the air bleeds becomes greater.... On the opposite side of the coin if the big bore/stroker applications where a LARGER air bleed can be more beneficial for proper fuel atomization and make complete use of the larger/higher velocity incoming air.....I for one am a BIG FAN of altering the air bleed once these particular mods are performed... more so if you go with straight bore vs taper bore (another long story). This is why if you bore your carb, you MUST run larger and larger jets... not because the engine all of a sudden needs a richer A/F ratio...but because you have reduced the carbs ability to provide such an AF mix...and therefore you must increase the jet sizes to COMPENSATE for a lack of pressure difference... reducing the air bleed size can significantly improve your jetting needs at this point.... and can usually bring back to life any lost 'low end' performance lag.... the main air bleed on the FCR is a fixed hole.... one of the mods which I highly recommend when boring your carb is to drill/tap the stock air bleed 'hole' to accommodate a JET, preferable the Keihin #100 air bleed jet which is used in the slow air bleed. I can attest it works quite well with most bored carbs and if not, you can simply change it out for whatever size suits you. By reducing the main air bleed, you can almost keep the same jetting as stock... I run a #168 main jet with a taper bored 42 FCR and #100 main air bleed. If you chose a smaller main air bleed, you could get away with the exact same main jet as prior to boring....this is a fine tuning aspect that has many benefits...

Also, you have what is known as a "starter jet"... this is the jet that increases fuel when the choke is pulled ON.. .remember, there is no actual "choke" in a traditional sense where a butterfly valve covers the inlet of the carb and CHOKES the incoming air off....hence greatly reducing the pressure inside the venturi and allowing the atmospheric pressure inside the float bowl to easily force additional fuel into the venturi.... on these carbs, when applying the 'choke', it simply opens up another "starter circuit" and allows for more fuel.....(I believe the book even calls this an enrichening device or something like that).... this is a great idea because it only increases the fuel slightly in the idle position while starting...and has very little effect at WOT... this means you can take off with your 'choke' on... and still ride your machine even at WOT application... whereas if you used a traditional choke.. the machine would be 'choked' to death and die....it also can be beneficial when determining MAIN JET sizes... run at WOT, both with 'choke' on and off...and see which runs better... if she runs better with choke OFF... then keep leaning the main circuit down until this stops... if she runs better with choke ON... then your already too lean...and go with larger main jet....(super secret squirrel jetting technique... ssshhhh)

Ok.....I hafta apologize again cuzz I was just going to discuss TERMINOLOGY... not go off another boring tangent.... but once I start typing...I just cant stop (its a disease, I know...lol)

and for those who are confused between Dynajets and factory Keihin...here is a useful guide...

Width------Keihin # -- DynaJets # -- Mikuni #
0,0350---- 92,5--------- 92----------- 86,3
0,0360---- 95----------- 94----------- 88,1
0,0370---- 97,5--------- 96----------- 90,0
0,0380---- 100---------- 98----------- 91,9
0,0390---- 102,5------- 100---------- 93,8
0,0400---- 105--------- 102---------- 95,6
0,0410---- 107,5------- 104---------- 97,5
0,0420---- 110--------- 106---------- 99,4
0,0430---- 112,5------- 108--------- 101,3
0,0440---- 115--------- 110--------- 103,1
0,0450---- 117,5------- 112--------- 105,0
0,0460---- 120--------- 114--------- 106,9
0,0470---- 122,5------- 116--------- 108,8
0,0480---- 125--------- 118--------- 110,6
0,0490---- 127,5------- 120--------- 112,5
0,0500---- 130--------- 122--------- 114,4
0,0510---- 132,5------- 124--------- 116,3
0,0520---- 135--------- 126--------- 118,1
0,0530---- 137,5------- 128--------- 120,0
0,0540---- 140--------- 130--------- 121,9
0,0550---- 142,5------- 132--------- 123,8
0,0560---- 145--------- 134--------- 125,6
0,0570---- 147,5------- 136--------- 127,5
0,0580---- 150--------- 138--------- 129,4
0,0590---- 152,5------- 140--------- 131,3
0,0600---- 155--------- 142--------- 133,1
0,0610---- 157,5------- 144--------- 135,0
0,0620---- 160--------- 146--------- 136,9
0,0630---- 162,5------- 148--------- 138,8
0,0640---- 165--------- 150--------- 140,6
0,0650---- 167,5------- 152--------- 142,5
0,0660---- 170--------- 154--------- 144,4
0,0670---- 172,5------- 156--------- 146,3
0,0680---- 175--------- 158--------- 148,1
0,0690---- 177,5------- 160--------- 150,0
0,0700---- 180--------- 162--------- 151,9
0,0710---- 182,5------- 164--------- 153,8
0,0720---- 185--------- 166--------- 155,6
0,0730---- 187,5------- 168--------- 157,5
0,0740---- 190--------- 170--------- 159,4
0,0750---- 192,5------- 172--------- 161,3
0,0760---- 195--------- 174--------- 163,1
0,0770---- 197,5------- 176--------- 165,0
0,0780---- 200--------- 178--------- 166,9
0,0790---- 202,5------- 180--------- 168,8
0,0800---- 205--------- 182--------- 170,6
0,0810---- 207,5------- 184--------- 172,5
0,0820---- 210--------- 186--------- 174,4
0,0830---- 212,5------- 188--------- 176,3
0,0840---- 215--------- 190--------- 178,1
0,0850---- 217,5------- 192--------- 180,0
0,0860---- 220--------- 194--------- 181,9
0,0870---- 222,5------- 196--------- 183,7
0,0880---- 225--------- 198--------- 185,6
0,0890---- 227,5------- 200--------- 187,5



Ok...nuff for now......Greg
 

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Heres my info
2007 450ER
Stock Motor
HMF slip-on
UNI filter
EHS racing lid
162 Main
3rd clip NGPR needle
Stock 42 pilot
55 leak jet
fuel screw 1 3/8 turns out
Runs PERFECT when moving, idles great, starts great, only thing I am not totally happy with is when in neutral and crack the throttle open real fast it just dies, still not sure on why but as 450rrr said before if the bike runs great when your riding it then thats all that matters.

Also Im at about 1000ft elev., and pretty hot and humid here in Iowa[/b]
Thanks. I am running with the air box lid off a 165 main and a 48 pilot(thats what HMF recommended) and it works great. When I crack the throttle open real quick, it doesn't die so maybe a slightly larger pilot might help. I would think the smaller leak would have helped that but I guess not.
[/b]
See i would maybe have thought that too but my fuel screw is set at 1 3/8 turns out and that is about 3/8 turns out from where the highest smoothest idle is (my method as learned from 450RRR for fuel screw adjustment is to find smoothest idle then back out 1/4 to 1/2 turns more) so with the stock 42 pilot and the fuel screw set where it is pretty much tells me a bigger pilot would be way too rich, I am kinda leanin towards accelerator pump timing or a smaller/richer leak jet. I would definitely like to figure out why it does it but it isnt really affecting the driveability of the machine so i dunno.

By the way, GREAT stuff 450RRR, its always an educational/informational read, keep it comin!!!
 

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greg, you have way too much time on your hands. lol another great write up though!
 

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Discussion Starter #17
greg, you have way too much time on your hands. lol another great write up though![/b]

well...not really... but its probably only gonna get worse... lol since I am now working the weekend/night shift.... I have all this time with nutten to do.... I mean... what does one do on a mon/tue/wed/thur????? you can only mow the lawn so many times...lol
 

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greg, you have way too much time on your hands. lol another great write up though![/b]

well...not really... but its probably only gonna get worse... lol since I am now working the weekend/night shift.... I have all this time with nutten to do.... I mean... what does one do on a mon/tue/wed/thur????? you can only mow the lawn so many times...lol
[/b]
write a book, put all this typing and good information into something you can make money off of :thumbsup:
 

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greg, you have way too much time on your hands. lol another great write up though![/b]

well...not really... but its probably only gonna get worse... lol since I am now working the weekend/night shift.... I have all this time with nutten to do.... I mean... what does one do on a mon/tue/wed/thur????? you can only mow the lawn so many times...lol
[/b]
You could divide your yard into 4-parts, spread it out over 4 days.....pace yourself.....lol.
 

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Greg, I was member here a few years ago when I first got my 450r, mostly lurking, searching for good info. I stopped visiting here for personal reasons, but I'm back. And your breakdown of jetting is one of the most thorough, comprehensive, easy to understand posts I have seen yet. Nice work.
 
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