Does the HPR 105.5 piston have a different deck height than the stocker? The pami does, so you can't put that in a sleeved cylinder. If the HPR piston will work it might be an option for a lighter piston than the JE or CP shelf pistons in a sleeved cylinder.

 

don't know about HPR piston.

the JE shelf piston (~105.0mm bore) is a very light piston design. I posted some pics in the past. for $160 it's hard to beat but only comes in 11.5:1 CR. i'm working with JE on the piston ring package - not sure the rings they send with piston is ideal.

http://forums.atvconnection.com/mess...hreadid=481573

 

I wanted a little more compression than 11.5, thats why Iwas wondering about the HPR. But for $160 I might give up a couple ponies and lighten my hubs instead. Thanks Dave[img]i/expressions/face-icon-small-smile.gif[/img]

 

That's a good point. Other than horizontal piston porting for reliable compression and precise CR, the weakest link is the rings.
And there is not much information on rings except lots of part numbers in JE manual. That alone may be reason enough to get the custom pistons.
May be mostly what piston designers do is calculate ring combination effects and complex interactions with the selected piston.

Sounds like a significant difference in performance/compression/reliability with the right rings alone. Two things I will require are customized pistons and exhausts. Other than 450r carb and sealed top end/head, that should be all I require for engine performance items.


Good Post Scooby. Thanks!!