high comp pistons

i was thinkin about a cp high comp piston for my crf250...i was wonderin if high compression pistons last longer or shorter than stock and what octane to run

I used them in my son's quad. The +5 made more power for sure and seemed to last long enough. We bought another one this year.

When you purchase a high compression piston, the manufacturer will more than likely tell you what octane to run. I would assume that they will tell you to run race gas and jet accordingly.

I used a JE high comp piston in my crf250x. It raised the comp ratio from 12.5 to 13.5:1. Very noticeable difference in low and mid power. I could get 50 hours from a stock honda piston before I really should replace it but currently have over 70 on the JE and looks like I'll get 100 easy, maybe more. I did rering it at 50 hours and it needed it. I've heard you can use stock honda rings on one of the high comp pistons, JE or Wiseco, but not sure which one. If it was time for me to replace the piston, there would be no second thoughts, the power and longevity are worth it. And I have no problem at all running pump gas and it didn't effect my jetting either.

My CRF250R with a Wiseco 13.5:1 piston runs fine on premium. I don't know how much of a performance increace it made because it was added with loads of other parts, but I have heard it gives you about 1 HP more through the entire powerband.

sweet looks like ill get one most likely..i got about 70 hours on my bike rite now so im gonna tear it down i gues..but i dont know why my valve clearances are still perfect even to i ride the shit out of it..oh anyone know the stock compression (psi) is so i can check it before i tear it down...i think im goin je they sound like the best

u have to run race gas though...i barely noticed a difference between my high comp piston and my wiseco.

u have to run race gas though...i barely noticed a difference between my high comp piston and my wiseco.

All you need is premium.

ok i got people tellin me 2 diffrent things..im not lookin for a lot of performance im just lookin to replace it and figured why not get high comp..so pump or race

You can run pump gas, as long as it doesn't ping on acceleration. I choose to use race fuel in my own bike because of many reasons, but it will run on pump fuel if it has too.

Depends on what the final compression ratio is. Since you haven't said how high people can't tell you.

well mine pings rite now when i run it almost at idle...whats that mean

I doubt its pinging at idle. Its probably piston slap your hearing. Pinging typically happens under a load with a warm engine.

search the crf250 forums. You will have no problem running on premium pump gas with a 13.5:1 piston. If you want to run race gas fine, but you don't have to.

i was thinkin about a cp high comp piston for my crf250...i was wonderin if high compression pistons last longer or shorter than stock and what octane to run

Well, it does increase the squeeze which wil raise cylinder pressure, especially after combustion. I assume you will be going from a 12.0:1 to maybe a 12.5 or 13.0:1? It will make more power, will put higher loads on the cylinder from the pressure exerted on the side of the cylinder from combustion, but overall, I dont think you will see any shortened engine life as a result. Oh, higher compression does mean you MUST use higher octane fuel. Its possible you may not be able to use pump gas anymore. I assume you are not using it for slow speed trail riding? If you run ther engine at lower rpm's, you do not want higher compression ratio. The engine needs a little more speed/inertia to roll past the compression stroke now. If you ride trails aggressivly, will be fine. Usually for every pro, there is a con. You need to find a nice happy medium.

with 12.5.1+ i would recomend race gas. compression that high during the summer season has pre-detonation on pump gas. which can cause ping, and wear & tear on the engine. just my $0.02

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