2010 crf250r what piston should i use

well its near time to change the top end in my 10 crf250r and was wondering what piston to go with stock or wiseco or anyother brands that are decent with minimal stress to my crank along with good quality

I ended up putting a stock in mine, but I didn't research the aftermarket stuff because I was busy with work.

I had 28 race hours on Wiseco 14,5-1 ,when i took it apart it looked like brand new

not even visible wear on the black coating

if you look for quality i would go wiseco

Kim

the wiesco has worked very well fot TUF racing they also sell them

My first choice would be Cosworth.

Wiseco, CP, JE, Cosworth are all good quality pistons. No matter which one you use, you can't go wrong.

ive narrowed it down to two brands doing some research,, im looking at a wiseco 14.2.1 ratio or a JE 13.8.1 or 14.2.1 do these pistons require race gas im pretty sure they dont but i want to ensure they dont before i order and which one would you guys run,i dont want too too much stress on the crank,would there even be a difference in power over the stock compression ratio let me know thanks

ive narrowed it down to two brands doing some research,, im looking at a wiseco 14.2.1 ratio or a JE 13.8.1 or 14.2.1 do these pistons require race gas im pretty sure they dont but i want to ensure they dont before i order and which one would you guys run,i dont want too too much stress on the crank,would there even be a difference in power over the stock compression ratio let me know thanks

If you are coming from a worn out stock piston to a new high comp. you will deff. feel a difference ,but how much a high comp. piston alone will give you over a new stock i cant tell

you can run pump fuel with the 14.2-1 but choose the highest octane availeble

Kim

If you are coming from a worn out stock piston to a new high comp. you will deff. feel a difference ,but how much a high comp. piston alone will give you over a new stock i cant tell

you can run pump fuel with the 14.2-1 but choose the highest octane availeble

Kim

At 14.2:1 your really pushing it with pump gas. Detonation really comes into play at that point. 13.5:1, I've heard that guys are getting away with 91 octane. I run 93 octane with 13.5:1 and have had no issues with detonation. The scary part is that I know in different parts of the US, 93 pump gas is hard to find. So take that into consideration. The other consideration is that if you do go with 14.2:1 and you experience detonation with 93 pump gas, where do you go from there? Now you have a bike that depends on $5+ per gallon fuel. You can either bite the bullet or change a brand new piston out to a lower compression. Are you racing this bike?

Kim, are you running pump gas with that 14.5:1?

What is the stock compression ratio for an 09? Does it vary from year to year?

what is the stock compression ratio for an 09? Does it vary from year to year?

13.1:1

13.1:1

Thanks. Ill be doing my first rebuild on my bike since getting it in july. It will be interesting to see what piston is in there. Hopefully I can identify it by the markings. And just replace with the same thing. Compression ratio that is. Will probably go with wiseco. Always had good luck with them in my jetski and my old cr250.

At 14.2:1 your really pushing it with pump gas. Detonation really comes into play at that point. 13.5:1, I've heard that guys are getting away with 91 octane. I run 93 octane with 13.5:1 and have had no issues with detonation. The scary part is that I know in different parts of the US, 93 pump gas is hard to find. So take that into consideration. The other consideration is that if you do go with 14.2:1 and you experience detonation with 93 pump gas, where do you go from there? Now you have a bike that depends on $5+ per gallon fuel. You can either bite the bullet or change a brand new piston out to a lower compression. Are you racing this bike?

Kim, are you running pump gas with that 14.5:1?

you are right you need 93 oct (99europe) ,as i remember its not only the comp.rate to look into

I only did a few hours on 99 octane (93 us) with 14.5-1 ,no problems with detonation , the rest of the time was on racefuel

But a friend of mine ran 14.2-1 the hole season with no issues using 99/93octane

there was a thread about this once and i think Ron said there it should do ok with 14.2 on the crf250

Kim

That's good to know. I'm still a bit on the fence with it. I built race car engines in the past and seen the damage that detonation does when the octane wasn't right. After seeing that kind of stuff, it puts fear in me. Going down a 1/4 mile track and having a failure is a little different than at the face of a 140' double! Luckily in these engine, I've never seen any damage that was caused by detonation. I'm sure they're out there, but I've never come across it.

That's good to know. I'm still a bit on the fence with it. I built race car engines in the past and seen the damage that detonation does when the octane wasn't right. After seeing that kind of stuff, it puts fear in me. Going down a 1/4 mile track and having a failure is a little different than at the face of a 140' double! Luckily in these engine, I've never seen any damage that was caused by detonation. I'm sure they're out there, but I've never come across it.

I think in a 250 the filling of the cylinder is not 100% because of the small bore ,cam duration ,rpm etc

even in a 450 i dont think its possible to run 14-1 with pumpgas

And start supercharge your carengine and it goes all crazy(guess you`ve been there:smirk: )

Kim

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