Piston?

[raptorman22]

Anyone know who makes a highcompression piston for the rappy?

 

[baja226sport]

how high of compression are you looking for? I believe JE makes a 12:1.

 

[raptorman22]

ok Thats the piston i was looking at. Are they good quality pistons?

 

[yamarider]

unless you want to spend $5 or more a gallon on race fuel, don't get a 12:1. JE makes a 10.75:1 piston, it's very good quality from what i've heard, and you can run pump gas with it. That's what's going into my warrior this month with the rebuild.

 

[warriorspeed350]

i dont understand all the numbers

 

[raptorman22]

where did u find a 10.75:1 piston at? I dont want to bore so i dont know if that piston will work. Plus a local dealer said that i will only have to run premium in it if i get a 12:1

 

[yamarider]

I never looked for one, I know they make them though because other guys on here have them. I'm pretty sure you can't run pump gas for a 12:1

 

[boxhead]

You will have to add octane booster in order to use the 12:1. I'm sticking with the 10.75:1 JE.

 

[DeathShadow]

where did u find a 10.75:1 piston at? I dont want to bore so i dont know if that piston will work. Plus a local dealer said that i will only have to run premium in it if i get a 12:1

WRONG - the cut off is at 11:1 still running premium - after that you should move to a race fuel/premium mix. The power dif between 11:1 and 12:1 hardly makes it worth spending that much money on fuel.

 

[raptorman22]

Ok thanks. How much $$ will the 10.75:1 run me?

 

[yamarider]

albaaction.com has them for $150. I'm hoping someone else has them for less, because $150 seems like too much for a piston.

 

[raptorman22]

ya $150 is quiet a bit. let me know if ya find one for less.

 

[warriorxcr1]

i dont understand all the numbers

i believe that the compression numbers equal the size of the length between the botom and top of the cylinder. when its at the top of the stroke its equal to 12 cm in between or some **** number. when at the botoom its 1/12 of that full stroke.

not sure about numbers but thats what that means- more compression equals more powerful strokes

 

[btownraptor]

Check Ebay....

 

[barlow96]

albas the only place ive ever found the je 10.75:1

 

[boxhead]

The compression is the volume of the air/fuel mixture at tdc as opposed to what it was at bdc set as a ratio. If your combustion chamber has 100cm3 at bdc and 5cm3 at tdc that would be 20 to 1 compression like a diesel motor. Usually the very high compression pistons will have a larger dome to reduce the volume available at tdc, that is why they tell you to check valve clearance. The dome on the piston sort of squeezes between the valves. Bigger the dome, less valve clearance and more compression. The often overlooked factor is the actual pressure inside the cylinder. If the psi level gets too high you're gonna blow a gasket clean out of the motor. I've actually seen a few motorcycles blow the gasket from running only 10.5 to 1 with the ignition timing advanced. The temperature running too high in conjunction with the already raised compression blew my boss's head gasket right out of the motor on the harley.