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Lord of Combustion
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Discussion Starter #81 (Edited)
It's amazing just how willing 4 stroke guys are to give out ideas. You'd be doing well to find this much info about 2 stroke porting in any amount of time. Other than macdizzy's site and camatv on Banshee HQ, nobody talks about their work. But I digress.
welcome to the sites where logic comes to die....

nobody shares much of anything on any atv site ... first off , only a handful actually know anything ... and then the rest run from knowledge like a cat runs from taking a bath....

everyone likes to talk about stuff they have bought... but very rarely will there be any test or comparative data to back up anything...

and over the past decade when i have went out of my way to share tech and explain engine dynamics....in doing so, you rile up the chromosome deficient... the same crowd that wants to promote, yet not understand, will all start screaming and throwing rocks like cavemen seeing their first helicoptor.....

now... to the porting sharing and info directly.... most like to act as though its some sort of VooDoo .... and if a picture is taken or shared ....it is viewed the same as some primitive cultures that believe a picture steals their souls.... and that they will have broken some secret circle of trust of some inner circle with sharing any sort of information...lol ...and of course shops like to promote that only a 7th degree back belt shahman can perform the rituals needed to raise the hp spirtits of the dead.... because that is what promotes ca$h register ringing.... not like its airflow (fluid dynamics)...has to be magic....

i have told people that if you can get something with a phone call and a credit card, it isnt any more top secret than a pizza.....

anyways... i do my best to pay back for all the information i have been so fortunate to have access to...and for the people who have given the time to help with my education... by taking the time to share what i can with the people who are curious enthusiasts and do it yourselfers....
 

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i have told people that if you can get something with a phone call and a credit card, it isnt any more top secret than a pizza.....
One thing that always amazed me is the amount of people who want to sell ported heads, but never show pictures, or who say their builders don't want them to let other people see pics. I can see a few reasons for not wanting to post port pics on the net, but for most riders I cannot see it ever mattering. jmo
 

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Lord of Combustion
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Discussion Starter #83
One thing that always amazed me is the amount of people who want to sell ported heads, but never show pictures, or who say their builders don't want them to let other people see pics. I can see a few reasons for not wanting to post port pics on the net, but for most riders I cannot see it ever mattering. jmo
lol... that's all part of the "if you take a picture , you steal someone's soul" sort of mentality...

in the rest of the motorsports world you will find publications with lots of info / details / pictures/ dyno documentation...

but for some reason this section of the sport ... with the most advanced machinery... stays in the "cold war" era of information.... no idea why that is
 

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Well, I'm not an expert, but I've done research on this stuff since I was really young. Outside of the guy that's teaching me how he ports 2 strokes (which differs wildly from how I've come to build them), I've found everything that I know online or through books. I've found what I like to do to both 2 and 4 strokes and I'm very happy with my results. Again, I'm no expert, but I'm grinding on cylinders every night so that I can find that golden port that so many builders have found for themselves.

I still give out my information for free, which is really a huge no-no in the eyes of most. However, I look at it like this: there will always be those who want to buy and those who want to DIY.

I recently started my own company, Acceleration Works. I port mostly, but I do other stuff as well. I offer to do the work myself and/or teach them how to do it themselves for free. Even then, 90% of everyone that comes to me wanting something ported just asks for me to do it myself and give them a jetting recommendation. Of the 10%, I've only had one that was interested enough to try it. Now if I told anyone that on another forum, they'd blow that off and still give me crap about teaching/spreading information, which is what a forum is meant for.

I mean, I can see a moderator protecting a site sponsor, but again, I've only ever lost business on one account of someone doing it on their own. Everyone knows that for a higher chance of a quality porting job, they'll have to send their cylinder or head off.

Mixxer, your posts and the lack of BS that you got for them are why I joined this forum. I wanted somewhere to document all of my grinding so that others can see what I've tried so that they can avoid the same pitfalls. Truth be told, every piece of information needed to design and create the near-perfect porting configuration is on the web, but it's scattered all over the place. My intent is to consolidate it into 2 places: here and blasterforum. Of course, there are a small few things that simply can't be divulged.

Rant over.

I have a thread going on that you commented on and I'm going to document everything that I do and the results. Do you or anyone else think it's too much stuff to post here? I may just finish that one up and post the consolidated version in this thread.

Also, the shop where the dyno is that I mentioned in my posts was sold yesterday, but they'll be getting another one in soon enough. They're a Honda dealership, so a back to back comparison of a stock one and the one I'm working on may not be out of the question. I don't like to see dyno numbers from different machines on different dynos, so this may be a good solution.

Do you still do work on 2-strokes?
 

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On another note...

If you really want to mess a builder up, send him one of your heads after you race him. It'll throw him all out of whack lol.

I ported a YFZ a few months back that had Hot Cams, pipe, open airbox, and my porting. The owner raced another YFZ builder and blew him away. Turns out, he was really rich on his jetting and the guy riding the one I ported was a far superior rider than his.

I recently sent him an extra head (victim of over-revving and detonation) that I'd worked on. It was just a bit of epoxy, chamber work, raised inlet, and more rounded dividers in the intake with a knife edge in the exhaust. There was no major port re-shaping. He called back and had questions out the wazoo. He texts me almost daily lol. He can't see the forest for the trees, but I won't tell him just how basic the port was on it.
 

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Lord of Combustion
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Discussion Starter #86
I still give out my information for free, which is really a huge no-no in the eyes of most. However, I look at it like this: there will always be those who want to buy and those who want to DIY.

I mean, I can see a moderator protecting a site sponsor, but again, I've only ever lost business on one account of someone doing it on their own. Everyone knows that for a higher chance of a quality porting job, they'll have to send their cylinder or head off.

Mixxer, your posts and the lack of BS that you got for them are why I joined this forum. I wanted somewhere to document all of my grinding so that others can see what I've tried so that they can avoid the same pitfalls. Truth be told, every piece of information needed to design and create the near-perfect porting configuration is on the web, but it's scattered all over the place. My intent is to consolidate it into 2 places: here and blasterforum. Of course, there are a small few things that simply can't be divulged.

Rant over.

I have a thread going on that you commented on and I'm going to document everything that I do and the results. Do you or anyone else think it's too much stuff to post here? I may just finish that one up and post the consolidated version in this thread.

Also, the shop where the dyno is that I mentioned in my posts was sold yesterday, but they'll be getting another one in soon enough. They're a Honda dealership, so a back to back comparison of a stock one and the one I'm working on may not be out of the question. I don't like to see dyno numbers from different machines on different dynos, so this may be a good solution.

Do you still do work on 2-strokes?
for a few years i had owned and operated Venom Performance... i took a detour from my career in medical physics and wanted to turn my full attention to my lifelong love of off road racing engines...

i changed the way everyone looked at piston performance by doing the work to model combustion chambers and tighten squish bands correctly...

the result was higher detonation resistance aided by the faster burn of more squish velocity and an unobstructed / fast burn chamber.... the tight squish meant you could have a more open "dome" and still achieve higher compression ratios...

the big domes block overlap flow and scavenging and also inhibit fast burn characteristics....

low tension rings and gas ports were also part of the perfect piston recipe..

i went to great lengths to explain this to the general public.... so they could come to an educated decision about what was important to power production beyond just a static compression rating....

bad idea .... the dumber the person was, the bigger the outcry against logic and information....

which was a bummer because i charged as little as i could for the custom pistons.... and it was an expensive porposition to order in big enough lots to get a price break... and have shelves stocked with different bore sizes and in pump gas and race gas compression...

the battle cry of the chromosome deficient was loud and relentless.... it made it very difficult to work in public forums.... too bad because the pistons out performed everything else by a significant margin.... the pump gas versions out performing all previous versions of race gas compression pistons...

and all based on information readily available in OTHER motorsports... yet cloaked in fog and myth in this one...

next up i used some basic principles of velocity / inertia / anti reversion / and a little bit of venturi and sound reflection to make the Venom Pipes... met all the 96db sound restrictions with no quiet core...
fully legal with sound and spark arrested out of the box...
highest torque / hardest throttle hit / widest band.... and the vacuum siganl generated and held by the system made it efficient enough to jet in with lower than typical jet sizes to achieve the proper AFR mixture...

the Venoms were so good at passing sound tests that at national level dirt track and desert races, the sound inspectors would just wave people through that had them.... shorten the lines for testing by giving a bye to the system that could pass all the tests and do it unrestriced and at full power....

BUT.... sadly.... the world at large is more interested in harley loud exhaust systems than having powerbands or throttle response.... and again the loudest voices come from the lowest common denominator....

i shared info on every possible subject.... from theory to dyno tests , to you name it.... and the more effort i spent to educate... the more education resistant haters came out of the woodwork to ruin and derail everything.... all of that took its toll on business and family....

and only stopping Venom and going back to physics full time has restored peace to the family base....

so now... that i dont make the pistons or the pipes , or run a dyno development driven shop...or have a huge info driven Venom sponsorship forum is.... the only time the haters have quieted down and let some information be shared ....

i make very good money in my physics career.... but i made the mistake of thinking my passion for both performance and education would make for a great business model doing something i have always enjoyed....

very regrettable idea....

i would love it if you honored this thread with further information and pictures from your own experience.... someone has to light a few candles in this dark fog ...lol .... i hope this thread helps people and de mystifies some of the misinformation this industry is cloaked in.... any and all help would be welcome...

and yes... i have always worked on 2 strokes .... gordon jennings "2 stroke tuners handbook" being one of my favored posession of my youth....

in 2 strokes there is port flow and port timing... the timing of the opening and closing of the ports is pretty much the equivalent of both port work and cam timing in a 4 stroke... only on a 2 stroke its all rolled into one...

and , of course, the timing of the exhaust port and the timing of the waves in the expansion chamber exhaust system are key in the power output of a 2 stroke
 

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The chance of something like that taking place is why I haven't devoted all of my time to my shop. I only do at night and when I have time on the weekends. Unfortunately, I've all but consumed the market around here and it's knocking on having no more business because there just aren't that many people around that want head work. When the local track shut down, everyone took a big hit. The only hope that I have for continued work is if the nearest shop will start sending business my way and even then, it'll be under the table.

I'll post pics around the 19th. That's when Hughes Net allows us to have full speed internet again... Retarded BS.

Anyway, the thoughts that I've had running through my head that pertain to 4-strokes for the past few days are concerning the combustion chamber. I recently tried a design with the chamber in which I decided to make improvements in flow from the valve seat to the rest of the chamber. I did this by making the material level with the chamber side of the seat. Though the butt dyno said otherwise, I know that something's up because it doesn't respond to timing changes as well.

My theory for this is that the flame front hits the valves, which are dead open to the rest of the chamber because I removed the surrounding material, creating a restriction for the flame front.

I tried a TTR125 head that I just got running and jetted and it pulls like a monster compared to stock. I re-worked the combustion chamber and left some material around the valves with a radius to them. The owner, who is a much more advanced rider than I, said that it was as fast as a CRF150R. I doubt it, but it does make the head swell.

It revs higher, pulls lower, and pulls another 7-8mph over the previous configuration. I machined the manifold down quite a bit on the top side to allow for a more down-draught style approach and added epoxy to the bottom of the SSI. I also added some to the spark plug side to make the flow swirl a bit and removed a great deal of material from the timing chain side. I also bored the carb as much as possible without going to nearly squared edges (has more height than width for stock).

If anyone knows anything about a TTR carb/manifold/head setup, you know that there are some severe angle discrepancies between the 3. Now, you can look down the carb and see the short side of the exhaust and I raised the carb so much that I had to remove the manifold again an machine the spark plug side down to get the carb to clear the frame. I was pretty mad that I had to port match again. I then had to modify the airbox mounts to keep the carb boot from coming off when it bolted up.

Before, it would wheelie in 2nd with coercion. Now, it wheelies in 3rd at any RPM and will pull 59mph. The most impressive thing about it is that you can slow it to below the normal idle and crack the throttle and it just pulls like it's scared of something. I posted the summarized process on thumpertalk (IIRC), but I never posted the final results because I got excited and assembled it. With the choke point, I went with a very, very streamlined shape with a choke point of a little more than 80%. I wanted to try 75%, but a slip of the wrist lead to a nice rut in the epoxy that compromised the 75% idea.

I did try 2 things with this one. One was the curve of the port on a horizontal plane (adding epoxy to one side, removing material from the other) and the other was that I did a short, fat bend that had the same floor contour as the manifold line. I didn't intend for it to be this way, but I think I measured it out to be an increase of the SSI radius by 3.5mm +/-.

As far as 2 stroke porting is concerned, I'm quite the fan lol. That's what takes up a good 80% of my thinking. I'm working on a 14 port stock Banshee cylinder design now. If that turns out to be my "golden port" that I described above, I'm not going to post the pictures that give all the info out, but I'll post some. Gotta save one configuration to keep the other builders up at night lol

I'm sure that you know just how much more secretive the 2 stroke side of things is than the 4-stroke side. You'll rarely coerce a general port description out of a top tier builder, much less figures and widths and durations. By rarely, I mean that I've gotten one builder to describe one major change to me in all the years that I've been into this stuff.
 

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Lord of Combustion
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Discussion Starter #88
I like your style, mr tfaith....

you and gobezio both have a huge working knowledge base on a wide range of engine dynamics....

i am very glad you guys are adding to this thread
 

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Hearing that certainly makes the day better lol. Thanks, Mixxer.

I thoroughly believe that anyone coming from porting 2 strokes to porting 4 strokes will do well. I may have a KX85 cylinder that I'll be posting in a different thread, probably in off topic or other bikes. This is of a higher priority than the 450R head because it's a paying job. Furthermore, if he likes it, he has a shed full of 2 stroke bikes that he said he'd send my way. I couldn't help but smile out of hopeful anticipation.

I may also be looking for someone to collaborate on with this KX cylinder. Are you interested, Mixxer?



Back to 4 strokes for a bit. I'm sure that the non-2-stroke crowd is getting bored with this stuff lol.

I'm a firm believer that the less timing needed for maximum power across the board, the better. MacDizzy said it best when he said that we should always strive for 0° of ignition advance. A lot of guys are probably wondering why I brought it up (and those will also google MacDizzy, The Enthusiast), but I think it pertains since those porting a head will, or REALLY SHOULD, have the head off, which is the best time to modify the combustion chamber. Altering the combustion chamber shape should improve on fluid flow, heat absorption, and flame travel. Since porting touches on fluid flow and since those 3 topics overlap more than anyone would like, I believe that it is highly relevant.

First, any time I say "timing requirements", I mean the amount of timing required to make the most power at a given RPM. Second, everyone should be aware that the type of engine at hand (450R) derives it's power from the expansion of gasses due to heat and not by an explosion. That being said, we want to create as much expansion possible by heating the gasses as much as possible. This is why an increase in power by 50% will result in an increase in heat production by almost exactly 50%. This is also why thermal coatings on pistons, sleeves, and chambers will produce more power. The common idea is that it reduces friction between the piston and sleeve, which is true, but it only accounts for a small portion of why it works better. What really happens is that the coating insulates the materials and retains the heat within the pressing gasses, which would otherwise soak into the piston, sleeve, and head, reducing pressure and ultimately reducing power. Short version: If we contain the heat, we retain the pressure and increase power.

If you've ever worked with a coated engine, you'll notice that you can reduce timing requirements by a few degrees and make more power because of the reduction in pumping losses. The cheapest option is to mirror polish all of the chamber and piston crown, but take heed that this will affect the last bit of atomization that the AFM will see before ignition. For leaner engines, I like to keep everything smooth, but those that run a little rich can benefit from a rougher finis. I mirror polish every 2-stroke that I'm given free reign to build, including those of mine. It also helps prevent detonation because everything is cooler AND because we can sometimes reduce timing requirements.

Now, before we can retain the heat, we have to produce it. Hopefully, we can do it as quickly as possible for the sake of power production. This is where flame travel comes into play. Since the largest factors to flame travel are combustion chamber geometry, contents, and RPM, we can be assured that any and all improvements to the combustion chamber will alter at least one of these three things. We generally don't run exotic fuels and aren't running forced induction here, so contents aren't so much a factor. We also run in a wide variety of RPM ranges, so target RPM doesn't come into play as much as with other engines. That leaves us with geometry.

Since this thread is for porting, I'd say to start with that, but Mixxer basically nailed that. Next, we have flame travel. This is where areas begin to overlap. A head that's been engineered to flow the very most with nothing else in mind may not necessarily have a design that is conductive of a fast burn, also called maximum squish velocity (MSV). I tend to come from an area that can easily separate flow and MSV (2-strokes) where the flow is down low and the burn is up top.

With that being said, I tend to lean more towards optimizing flow, but have more of a concern for MSV with 4-strokes because the subjects overlap. Truth be told, I'm more focused on MSV than flow in the chamber because of my background. Too much, almost. Think of some F1 engines where it was told that the piston came close enough to the head that the spark plug's ground was the piston. That implies 2 things: one, the squish clearence is very tight, and two, that there can't be too much advance if that actually is the case. The mind boggles...

I'll get on to the practical side now. Much like the ports should be free of major obstructions, so should the chamber. This includes the head, valves, sleeve, and piston since they all see the action. If anyone comes up with a way to improve on the sleeve for MSV, I'm all ears. Until then, let's focus on the rest. Up next, valves can't be improved upon too much because the rounded lip absolutely has to shed heat. If you shave them down flat to make the chamber as free flowing as piossible, you're going to have some very sharp edges just hanging out there for hot gasses to soak into AKA not good. So we have the head and piston crown.

Be aware that taking too much material away will reduce compression, which will result in a slower burn. Higher compression configurations place all of the gasses closer together, resulting in each molecule seeing radiant heat quicker. Remember, heat is what we're after, so keeping everything together is a must. However, a faster burn with lower compression is roughly equivalent to a slower burn with high compression. We aren't after compression, really. We're after faster burn, which compression aids. As a side note, the higher compression also places all of the expanding gasses in a smaller area, therefore increasing pressure to aid the downward travel of the piston. See just how encompassing heat and pressure production are? Eh?

Now if you take the 450R head for example, the spark plug is recessed. This is a design that I don't like. However, it does shield the plug from direct exposure to cold, wet gas, which I can tolerate. But in the end, I'm going to make the transition from the spark plug area to the rest of the chamber more streamlined. This will aid flame travel, I think. See, if the flame travels downward, it creates turbulence in the chamber when it slams into the piston, which will ensure that each molecule has a higher chance to burn and radiate heat to even more molecules. On the other hand, a direct path will allow the burning molecules the same opportunity to affect other molecules because they're traveling outward because from the spike in pressure at the plug at ignition. As such, I like to think that a straight path will allow more radiant heat to be dispersed evenly, increasing MSV.

So it's up to you there. You can either keep the plug shrouded or open it up a bit. Unfortunately, there isn't much room to play with.

Now the edges of the valve shrouds play a huge factor here, but I haven't quite put my finger on what's happening. If I could, I could design a better shape. However, I do know that from my 2-stroke days that obstructions = bad. The almost 90° bend fromt he shrouds to the flat surface of the bottom of the head can't possibly help MSV, but I may be wrong. The only thing keeping me from smoothing it out altogether is that I haven't tampered with deck height and squish clearance with very many 4-strokes. I think that the squish clearance will be a hand-in-hand endeavor with altering those edges, but I have other things on my mind.


Keeping in line with the above (fluid flow, flame travel, heat absorption), we haven't touched on heat absorption in a way that matters to those with a carbide spinning. To be quick, sharp edges are bad for all three areas in equal proportions. Sharp edges will absorb heat and create hot spots. In severe cases, this will induce pre-ignition = 5 minutes till rebuild time. Some people can come up with reasons as to why everything I mentioned above is complete BS, and they should for sake of intellectual discussion, but no one can argue there. High spots will absolutely absorb more heat, no exceptions.

Keep in mind to balance the 3: fluid flow, flame travel, heat absorption. A few hours of critical thinking will answer most of your concerns before you grind. Alternatively, share your questions/findings/concerns here and keep this thread alive.
 

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Great post !!
As you said it's a matter of balance, on the coatings subject, we discussed this in another thread, I like to call it a religious matter lol, it has advantages and drawbacks.
I mentioned the link between heat retention and efficiency before and I agree that the hotter the charge gases for the longest period of time during the effective power stroke will increase power and it's a mathematical fact. Think of the Aera under the cylinder pressure curve.
The problem in the 4 strokes is the tendency to retain too much heat during compression and induce detonnation and quickly get into diminishing returns.

Four strokes (and maybe even 2 strokes) should aim to get Maximum Cylinder pressure very close to 14° ATDC, we get real close by using the less timing for best power for any RPM ranges.
 

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Yes I have seen those, bore size is quite close !!
They have interesting profiles and are not as big ports as we would think for a 18K rpm motor.

I have read on the same site that the injection pressures are limited to...300 bar this year, so I think that they use the injection pressure to "supercharge some" the intake charge.
With the same technology we could expect a 250hp motor lol
 

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Question: I was told by a builder that once he decks my head it will end up being 13.5:1 and pump gas friendly all day long... He said he takes multiple steps to prevent detonation and jets them on the fat side, and he says he even has motors on 14:1 running on pump gas!

"With a flat top piston and decking the head you achieve the same "fast burn" chamber without race gas."
"It is much easier for the combustion flame to travel across a flat surface than a high dome with radical valve pockets"
"I do multiple things to prevent detonation. I actually have 14:1 motors running on 93 pump gas, they gotta be jetted on the fat side but they run like a scalded cat
Nope, beat the tar out of it. I'm not a whiny builder, I've learned to make engines take the "Barcia" style of abuse. On pump gas"

What's your guy's opinions on this?
 

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Question: I was told by a builder that once he decks my head it will end up being 13.5:1 and pump gas friendly all day long... He said he takes multiple steps to prevent detonation and jets them on the fat side, and he says he even has motors on 14:1 running on pump gas!

"With a flat top piston and decking the head you achieve the same "fast burn" chamber without race gas."
"It is much easier for the combustion flame to travel across a flat surface than a high dome with radical valve pockets"
"I do multiple things to prevent detonation. I actually have 14:1 motors running on 93 pump gas, they gotta be jetted on the fat side but they run like a scalded cat
Nope, beat the tar out of it. I'm not a whiny builder, I've learned to make engines take the "Barcia" style of abuse. On pump gas"

What's your guy's opinions on this?


Well are we talking 2 or 4 stokes, and yes---if you have a custom made piston you can run them 13.5:1 but it depends on your elevation,,, with 93 oct...

But im not in favor of just makeing just one pass---on any machine and just go limp,,,just not my stlye...
 

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Question: I was told by a builder that once he decks my head it will end up being 13.5:1 and pump gas friendly all day long... He said he takes multiple steps to prevent detonation and jets them on the fat side, and he says he even has motors on 14:1 running on pump gas!

"With a flat top piston and decking the head you achieve the same "fast burn" chamber without race gas."
"It is much easier for the combustion flame to travel across a flat surface than a high dome with radical valve pockets"
"I do multiple things to prevent detonation. I actually have 14:1 motors running on 93 pump gas, they gotta be jetted on the fat side but they run like a scalded cat
Nope, beat the tar out of it. I'm not a whiny builder, I've learned to make engines take the "Barcia" style of abuse. On pump gas"

What's your guy's opinions on this?


Well are we talking 2 or 4 stokes, and yes---if you have a custom made piston you can run them 13.5:1 but it depends on your elevation,,, with 93 oct...

But im not in favor of just makeing just one pass---on any machine and just go limp,,,just not my stlye...
This is for my trx450er, running 12.5:1 cp sb piston. my elevation is around 900-1000
 

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First off I literally registered to this site to say thank you to Mixxer, CFM and the others on this thread for all they contributed to the public, Thanks Guys! You all definitely took allot of time to help out those of us that are less experienced.

I used to race MX on a Banshee and later on a 08 TRX. Simply put in MX I would not trade the low and mid power of a bike for anything, running a Banshee in the dark days was WAY more work than the 08 TRX. This thread has a ton of great info on making usable power.

Thanks again!
 

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Mine ended up at [email protected] rpm, had 40+hp from 6k to 10k RPM, 11,7:1 comp, SB/SS, stage 2 cam, stock valves (yep the 2008 ones), a chain that would stand up by itself.
I think that a lot more intake duration would have helped a lot to get more top and mid.
it would pull the front end up out of the corners every time.
 

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Discussion Starter #98
On the topic of high compression and pump gas.. Its just like dancing in a mine field... Everything is great until the split second where nothing is great anymore....
Its like saying you have never gotten a disease from unprotected sex... Good for you, but odds are not in your favor... Plus if the risk is worth it, then ride on , but don't recommend it to others

Totally not worth it.... And also stupid to blanket say you can run any compression number on pump gas without knowing all the particulars....

Long duration cams bleed off low rpm intake charge and lower pressure...

High altitude makes for less cylinder fill... So less dynamic compression which the same static comp ratio...

Smaller bores have faster burn from side to side... And naturally can run more comp safely

Richer air fuel mixtures dampen the burn and lower your power... But also let you run higher compression.... So its really shooting yourself in the foot to chase high comp for power and then kill the power with rich jetting on pump gas....

Also, ride style and engine load from hills to deep sand , as well as the rpm you are accelerating from will all make a difference in what compression you can run safely..

Also... Your actual power level... Low power combinations tolerate higher compression because the lower power engines are lower lower because they have a.lower volume of intake charge .... Less cylinder fill means less actual compression pressures no matter what the static rating is on your piston...

Anyways.... Sick to death of all the stupid recommendations to run pump gas with higher compression.... None of it is worth trashing an engine over the 1hp differdnce
 

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uploadfromtaptalk1426890323837.jpg
For the life of me I can not find these things to buy anywhere. A friend of mine loaned them to me for a while but I've been trying to find my own set. Said he bought these years ago at a place called CNC Specialties
 
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