Aftermarket Piston Selections??

[backfire]

Does anyone know if there are any sort of aftermarket piston selections readily available for the VMax- high compression or otherwise? Thx!

john

 

[shawn kloker]

Yamaha sells 77mm and 78mmoverbores. Arias has them wich Sean Morley sells and JE makes them wich PCW sells.

 

[backfire]

Thanks for the reply. I found the JE's that PCW carries from PCW's website, but there were no detailed descriptions of them other than the listed compression ratio. Also, I didn't find anything from Arias's website, nor at Morley's website either.

Does anyone happen to have a description or listing for the Yamaha parts?

I'm asking because I'm interested in a set of aftermarket, high performance forged pistons for my machine. However, I need to know what I'm getting by seeing some specifications before I buy.

If I can't find anything, than I'll engineer a set of them here at the shop, (we have that capability here) but I'd rather not have to re-invent the wheel if I don't have too.


john

 

[shawn kloker]

You'll have to call Sean.I do know that the after market pistons are only for the 1260cc and larger.I put the 1 mm over yamaha pistons in mine.1230cc.Dirt cheap from U/Motors.I kind of regret it now,that with not decking my block while I had a chance.After market pistons will be over $500 without rings.I think I bought my Yamaha ones for $45 each with the rings.

 

[backfire]

For those that do install larger aftermarket pistons..what are they doing to retain the factory engine rotating assy. balance? Larger pistons/rings/pins would be of course heavier than the stock parts.

To give you an example~
I have a 2007 Honda Rincon 680cc 4x4 and I wanted an aftermarket, forged, higher compression than stock, drop-in replacement piston for that engine to boost low-end performance, but there wasn't any to be had anywhere from the aftermarket.

Soooo, with the consultation/assistance of a major piston manufacturer, we engineered one here based off the stocker dimensions, only we produced it from a light-weight forging that retained the factory weight match of the stock slug within 1.7 grams, in an effort to retain the factory engine balance for smooth engine operation. Worked like a charm and the engine runs even smoother than it did stock, plus it pulls much harder down low from the added compression hike.

 

[shawn kloker]

I would have also machined the counter balance shaft wieghts off also.

They totally remove this shaft when building high perf Busa motors.Gains them like 10 hp.

 

[backfire]

Re-balancing the engine would be the logical thing to do of course, but from what I've read all over the net, most folks are only upgrading the upper-end of the engine without doing anything to the lower end. I can't figure out how they are getting away with it...at least from an engine reliability standpoint anyway. :confused2:

 

[4gasem]

I bet the stock crank is pretty balanced... Well depending on the year of the bike.

My buddy is building a 300+hp civic and had his crank balanced and the builder was amazed how balanced it was stock. He was able to get it closer but said it was 3 to 4 points closer than most American cranks...

The Japs are amazing engine builders...:thumbs up:

 

[backfire]

I know the cranks on any engine are balanced, but they are balanced to the overall crank pin bob-weight of each reciprocating piston/connecting rod/conn. rod fasteners/conn. rod bearing/piston pin/piston pin circlips/piston ring pack and approx. 4 grams for retained oil weight. All that reciprocating weight is generally what each crank counterweight weighs to match each pair of piston/rod combos for a given crank pin, +/- a few grams...which is what final balancing is for to fine tune it in.

The more one deviates from stock with the above combination using other aftermarket parts with different weights, the farther away from "neutral" the rotating assembly gets from its original balance using the stock parts as the reference point.

On the auto drag racing engines we build here, if the crankshaft counter-weight weighs less than the reciprocating bob-weight, we generally have to add Mallory-metal to the counterweights to match the recip bob-weight evenly, otherwise the engine will shake itself apart, eventually knock out the main bearings and it won't make as much power as a fully balanced, smooth running engine would.

That's how I can't figure out how they are doing it without the engine shaking itself apart over time. Maybe they can't feel it much at the handle bar to even know (or care) if its an issue? :hmmm: Just an observation I guess.


john

 

[one2dmax]

All the components are "Nuetral" balanced.

The pistons I sell are withing 1 gram usually and the stock rods are also very close to each other. Though there is increased vibration you can even remove the counterbalace shaft (actually cut off the weights) with no real ill effects.

I've got a set of 1261 pistons on hand that are about 1/2 a point in compression increase and will fit in your block with only a bore. Any larger and you have to change sleeves. I can get any combiniation you want though I don't have a lot on hand. You can mill the block while you have it apart to also increase compression and "Squish".

Sean Morley

 

[backfire]

Thanks for the reply Sean and I'll keep you in mind when I'm ready to tear this thing down this Fall. I'm sending the O.E. crankshaft to Falicon, we'll be re-working the O.E. rods here for re-use and I've got another set of O.E. heads to port that will go on the engine to top it off. I'll get with you on camshaft selection also when the time comes.

I've got a ride out West later on in the Fall, so I don't want to take the machine down until after that time and we only have about 6-8 weeks more of decent riding weather around here yet this year. I've got a 2008 Max on order to ride next year if my '95 isn't done by then and when it does arrive, I'm going to turn the '95 into more of a strip bike overall just to have some fun with.

Thanks again.


john

 

[shawn kloker]

Thanks for the reply Sean and I'll keep you in mind when I'm ready to tear this thing down this Fall. I'm sending the O.E. crankshaft to Falicon, we'll be re-working the O.E. rods here for re-use and I've got another set of O.E. heads to port that will go on the engine to top it off. I'll get with you on camshaft selection also when the time comes.

I've got a ride out West later on in the Fall, so I don't want to take the machine down until after that time and we only have about 6-8 weeks more of decent riding weather around here yet this year. I've got a 2008 Max on order to ride next year if my '95 isn't done by then and when it does arrive, I'm going to turn the '95 into more of a strip bike overall just to have some fun with.

Thanks again.


john

John,If you are going all out with this engine I would get the good rods.

 

[backfire]

Who carries those (Sean I presume) and what brand are they?

 

[backfire]

Never mind, I found them...Carillo? Geez, they are pretty proud of them aren't they- $1200 for only 4 rods?? I can purchase a set of Carrillo rods for a stroked LS2 415 V8 engine for the same cost, but get twice as many rods!! :surprise:

 

[one2dmax]

Carrillo has two different levels of rods. One level - "A" beam is good for approx 50hp per cylinder - about $800 per set. I do stock reworked OE rods. We bush the small end and resize the big end. I have a few sets on hand already ready to go $240 exchange.

Sean

 

[backfire]

Wow Sean, sounds like you're the guy I'll come to when I take this thing down and $800/set is far more pallatable. Thanks for the information and the time.

john