Honda TRX 450R banner

1 - 20 of 80 Posts

·
Registered
Joined
·
11,022 Posts
i forgot the list so mixxer willhave to fill that part in i know the venom pistons have forced pin oilers and lateral gas ports lol
 

·
Registered
Joined
·
809 Posts
They are gas ported. The valve relief channels are specifically a Venom design. The compression specs are Venoms specs.

To be honest, the Venom pistons made by CP were out with all the goodies you see on the current CP shelf pistons before CP started stocking these upgraded shelf pistons. Now Venom still has some other things built in to their pistons thats not in the shelf pistons. Some mentioned above.

None the less, there different.
 

·
Registered
Joined
·
809 Posts
Hell it wasnt all that long ago when 14:1 compression pistons were just an wishful idea.

Now theres a 14:1 waiting around every bend.

It was Kam of KBR and John/Mixxer who got that trend going. No BS....
 

·
Registered
Joined
·
10,711 Posts
There are other subtle differences as well......

which John may or may not want mentioned on here.......ill let him add to the list.....
 

·
Admin
Joined
·
2,546 Posts
Nitrided (sp) rings, under dome milling for less weight and faster reving, gas ports for stronger ring seal, I believe the wrist pins weigh a lot less too. Anyhow thats all I can think of right now.
 

·
Registered
Joined
·
1,025 Posts
so if you get a ventom piston or any other than stock piston. should you have the crank, rod and piston balanced. or can you just add and go?

i really like what the venmon piston looks like .......fast.
 

·
Registered
Joined
·
3,557 Posts
so if you get a ventom piston or any other than stock piston. should you have the crank, rod and piston balanced. or can you just add and go?

i really like what the venmon piston looks like .......fast.[/b]
Most people just throw the piston in and go. BUT, it's always better to have the crank balanced to the piston because most aftermarket pistons are going to be much lighter than the stocker.
 

·
Registered
Joined
·
10,711 Posts
the weight differences..... other than a lighter piston can rev up higher and reduce (robbed HP) because of its constant stop/go process...... will not effect the reciprocating motion/mass of the crank.....

remember....the piston is not spinning along with the crank......so it is not part of the 'rotating mass' equation...... the most difficult aspect of balancing a crank is the rod.....cuzz it IS attached to the crank and it is the one piece that has two significant changes taking place at the same time......the lower rod portion is spinning in a direct fashion with the crank.... (and has the most effect on the balance and rotating mass)....the upper rod bearing portion is not spinning at all....and only moves up/down with the piston......(and has the least effect on balance and rotating mass).......and this movement is transformed between the lower rod and upper rod......

the Crank.....in most vehicles... .should be balanced to other reciprocating parts such as the flywheel... crank gear... etc.... (clutch pressure plate and harmonic balancer in a car)......

then comes the 'counter balance shaft/weight'.....another segment in the balancing act....



so before you go changing your flywheel.....think about balancing the entire assembly...

but for just a piston.... your good to go....


jmho...me~
 

·
Registered
Joined
·
1,025 Posts
the weight differences..... other than a lighter piston can rev up higher and reduce (robbed HP) because of its constant stop/go process...... will not effect the reciprocating motion/mass of the crank.....

remember....the piston is not spinning along with the crank......so it is not part of the 'rotating mass' equation...... the most difficult aspect of balancing a crank is the rod.....cuzz it IS attached to the crank and it is the one piece that has two significant changes taking place at the same time......the lower rod portion is spinning in a direct fashion with the crank.... (and has the most effect on the balance and rotating mass)....the upper rod bearing portion is not spinning at all....and only moves up/down with the piston......(and has the least effect on balance and rotating mass).......and this movement is transformed between the lower rod and upper rod......

the Crank.....in most vehicles... .should be balanced to other reciprocating parts such as the flywheel... crank gear... etc.... (clutch pressure plate and harmonic balancer in a car)......

then comes the 'counter balance shaft/weight'.....another segment in the balancing act....



so before you go changing your flywheel.....think about balancing the entire assembly...

but for just a piston.... your good to go....


jmho...me~[/b]

good info , i thought that the weight of the piston would make a differance in the harmonics of the rotating mass. that the crank was balanced with piston weight in mind.

i'm use to doing 8 pistons, they need to weigh the same so not to put crank assy out of balance. i have to change my thinking alitte here..1..... so what your saying is a lighter piston will will not effect the balance of the crank. it will just give alittle more hp and turn up quicker. but is their a point where it's too light provided it is strong enough to take punishment?...just thinking out loud.......
 

·
Registered
Joined
·
3,557 Posts
the weight differences..... other than a lighter piston can rev up higher and reduce (robbed HP) because of its constant stop/go process...... will not effect the reciprocating motion/mass of the crank.....

remember....the piston is not spinning along with the crank......so it is not part of the 'rotating mass' equation...... the most difficult aspect of balancing a crank is the rod.....cuzz it IS attached to the crank and it is the one piece that has two significant changes taking place at the same time......the lower rod portion is spinning in a direct fashion with the crank.... (and has the most effect on the balance and rotating mass)....the upper rod bearing portion is not spinning at all....and only moves up/down with the piston......(and has the least effect on balance and rotating mass).......and this movement is transformed between the lower rod and upper rod......

the Crank.....in most vehicles... .should be balanced to other reciprocating parts such as the flywheel... crank gear... etc.... (clutch pressure plate and harmonic balancer in a car)......

then comes the 'counter balance shaft/weight'.....another segment in the balancing act....



so before you go changing your flywheel.....think about balancing the entire assembly...

but for just a piston.... your good to go....


jmho...me~[/b]
Why then do companies like crankworks, need the piston in order to balance the crank? It makes total sense to me that the weight of the piston DOES have an affect on the balance of the crank.
 

·
Registered
Joined
·
10,711 Posts
I cant say for sure Bueller....... you would probably have to ask one of the crank companies.... but remember, whatever answer you get, MIGHT just be for BS purposes.... im sure a totally different weight of a piston... maybe going from an extremely heavy stock 05 piston....to a much lighter slipper skirt style piston.... MIGHT make a LITTLE bit of difference..... BUT, I also know...over years and years of building engines.... that I have never had a balancing issue when changing pistons..... after all... Pistons are a wear item.....and they get replaced quite often.... unlike cranks and rods, etc..... and, along those same lines, is the simple fact that you can purchase pistons on a consistent basis, w/o ever knowing what they weigh, and yet NO piston manufacturer that I am aware of claims you must now have you crank balanced to match these new pistons.....

however....there is a claim from Hot Rods that you cannot use HIGH compression pistons with their cranks, but never any mention of how much your piston must WEIGH, in order to maintain the balance of the crank assembly......

see if this makes sense..... and NO, I am not saying I am 100% correct....and they are 100% wrong... just listen to my explanation, and if it doesnt make any sense...then simply ignore my information and assume you must continue to balance the piston with the crank....

ok...here goes.....

the Piston only goes UP and Down.....so if it weighs a little bit more....or a little bit less.... lets try and figure out the outcome of this weight on a crank...

*piston on top traveling downward.....

as the crank reaches TDC....and is now being pushed downward as it rotates past this point.......there will be added weight on the crank journal pushing it downward...(from the extra weight of the piston)....causing it to become out of balance....correct?

NOPE..... remember how insignificant this weight would be given the extreme force being pushed downward on top of that piston from the combustion process.......no amount of extra weight could accommodate for such a load...not to mention this load would VARY with each and every combustion cycle cuzz it would NEVER haveexactly the same amount of pressure during combustion....even if you could manage to maintain a steady throttle......which we dont... we add and subtract throttle input...which in turn adds/subtracts the amount of force being pushed down on the piston....so who cares about 10 or say grams of weight......


** piston on bottom being pushed upward....


on the other end of the rotation......the upward stroke or compression stroke..... now the crank must force a heavier piston to travel upward during this stroke......so, we can assume that this either heavier or lighter piston would throw off the balance of the crank at this point..... well, not really..... and here again is why.... yes, the piston may or may not be marginally heavier/lighter... however, this makes almost no difference in the grand scheme of things..... once that piston begins to compress the a/f mix....it adds a TREMENDOUS amount of pressure in comparison to just the additional weight of the piston..... and, remember, as we all love to mod our bikes and ALTER this compression or PRESSURE amount....... which would GREATLY alter the balance of this crank...if in fact it actually mattered... which it doesnt.....not really.....

think of it this way........a layman's explanation... cuzz I really dont have all the facts/figures and fancy words to explain it any other way.....I am after all...just a backwards old school person....... but hear me out...... remove your spark plug...and kick over your machine....when you kick over your machine...you are turning all the parts of the engine.... goes over rather easy w/o compression....and for the most part you cant really tell where the piston is....or when your at TDC or BDC etc.... now think about changing to a new piston....and adding/subtracting lets say....10 grams.... okay.. lets go all the way and say we just took out or 05 stock BOAT ANCHOR of a piston with 10.5:1 compression......and just put in a brand new Venom slipper skirt Big Bore 100mm piston at 14.25:1 compression..... must of saved at LEAST 50 grams on that deal..... now kick the bike over again...with no spark plug....... guess what... you cant really feel the difference in this rotating mass......... now put back in the spark plug.... and HOLY SCHNIZZLE..... you can REALLY notice a huge difference now...... WHY? cuzz the compression makes FAR MORE of a difference to the actual 'load' of the crankshaft than a few grams of weight does.....a HUGE difference....... and THIS is why some manufacturers say you should not use HIGH COMPRESSION pistons....yet they never mention anything about the actual piston weight...


again....I aint an expert...or a guru....or an engineer..... or even an engine builder....... just an enthusiasts...... but I do have some 'common sense'.....and this tells me that the actual Weight of the piston has very little...if anything... to do with the balancing of the rotational mass inside this engine...



now if that dont make any sense...... then by all means.... have your pistons balanced to your cranks.....


jmho.....me~
 

·
Registered
Joined
·
495 Posts
Calculating bob weights isn't difficult, but it does require a littletime at the scales. Here's the complete list for determining your bobweights for zero-balancing a crank.

Rotating Weight
* Big end of rod (including fastening hardware)
* Bearing
* Oil (normally estimated at four grams)

Reciprocating Weight
* Piston
* Wristpin
* Pin locks (if used)
* Small end of rod
* Piston rings

Bob weight = Rotating Weight + (Reciprocating Weight x .50)
 

·
Registered
Joined
·
10,711 Posts
I am familiar with 'bob weights'..... and they are not used in all engine applications.... usually V-8/6 type engines due to an irregular offset of the crank.... they are not needed in most 'in-line' engines.... as this type of crank utilizes opposing cylinders/pistons to offset each other....... you also hafta ask the question as to whether or not these engines are internally balanced...or externally balanced...... otherwise the flywheel would play in important role in the balance.....


I am not saying that a crank company would not want your piston (full weight with rings, pin, etc) and current Rod (if not already attached to the crank) in order to perform a complete balancing job on your single cylinder crank.......

what I am saying is that I HIGHLY DOUBT the weight of the piston has any 'real life' impact on the balance of a single cylinder thumper engine......... as I explained above.... a crank rotating in the balance machine with bob weights to dial it in is one thing....and that is all good...... but there are NO 'Dynamic forces' being applied during this process....

but a working crank...inside of your engine.. with all the forces I explained above.... the added pressure during combustion forcing that piston downwards... the added pressure of that piston being forced again during the compression stroke......not to mention your bore diameter (cuzz a larger bore = more drag).. the differences in drag between 2 and 3 ring pistons as well.....and so on and so forth.... remember...the Piston, does not Rotate..... it merely travels up and down....so ANY force.. whether it be more or less weight....or added compression or combustion....or more/less drag.... etc... will effect the Rotational mass of the crank.... to such a point that it could never be calculated due to ever changing events occurring w/in each cycle of the engine.....

its kinda like this.....why isnt a bigger port better than a smaller port in all aspects.....or a free flowing exhaust...or better yet....NO exhaust at all..... better than a restrictive exhaust with back pressure? its simple.... its called engine Dynamics.... and they are ever changing within the engine......

yes...you can control a crank spinning all by its lonesome on a balancer machine.... but you cannot control the FORCES being placed on the large rod journal end during each cycle of the engine...... and THIS is why.... at least in MY opinion and with my experience..... the weight of your piston has very LITTLE effect on the rotational balance of your engine while it is actually operating.....

If it did...the weight of your stock piston... would be highly advertised... as would the exact weight of each and every after market piston available for your machine..... some say companies try and make their pistons as close to OEM as possible.....yet most high performance pistons advertise how much LIGHTER they are than stock... etc.....

again.... I know what the 'book' says....and im sure its correct.... but for me.... I will never worry about the weight of each piston I install in my machines.... except I want the LIGHTEST piston possible than can still hold together..... and by the way... that is exactly what I am using......


this is just my opinion........ like I said... if it dont make no sense... ignore me... im an idiot.....
 
1 - 20 of 80 Posts
Top