Jump to content
Sign in to follow this  

high comp piston vs stock

Recommended Posts

seems as if i may replace my piston while i am doing my valves. i am thinking about going with the hihg compression. can someone tell me the pros and cons. will it be harder to kick? will the power be noticed? or will it be all top end power? or should i just stick with the stock? thanks

any help will be appreciated.

Share this post


Link to post
Share on other sites

can anyone help me here? i am going to order later today, can some one talk to me about the benifits of the high comp piston? what do you guys think wiseco or JE? thanks

Share this post


Link to post
Share on other sites

Ok, I am not an engine guru by any means, but I read your post and looks like you need info. quick. I believe that a higher compression piston means more low end grunt. Also, this can put more stress on your bottom end, but how much quicker it will "wear it out" I don't know. Now, I am going to be purchasing a 14:1 J/E piston soon and I was told that I needed to run different gas with it all of the time (to realize the power increase). I also know that every person has different beliefs when it comes to the gas on a high compression piston and I am not saying my way is the only way. For practice I can run 110 or 112 octane with 91 pump gas 50/50. For race day situations I will be running U4.2. So, if you are looking for a little more power this might be an option for you. I hope I have helped.

Share this post


Link to post
Share on other sites

thanks man, it is my understanding that the 13.5 will be fine on 93. i always thought that the higher comp piston would place more strain on the rest of the motor. but when i researched this ( in the fall) it seems alot of guys were saying that it did not. so i dont know. i am new to this 4 stroke dirt bike stuff. thanks for the reply.

Share this post


Link to post
Share on other sites

Your welcome. I am with you in that I think along with more compression comes a greater load on the bottom end, but I am not an engine builder. Btw, I am going with a J/E due to preference. Hope everything works out for you.

Share this post


Link to post
Share on other sites

i have alot of experience with two stroke stand up jet skis. and i always run wiseco in them when i rebuild them. but i think for my crf i am going to buy the JE. i would really like to hear someone comment on the high comp piston adding strain onthe bottom. anyway thanks again man

Share this post


Link to post
Share on other sites

My JE is on the way, 13.5:1.. this will be the bikes first rebuild as well as a first time high comp piston user. Look at it like this, the 08''s and 09's are running 13.1:1 compared to a 06 or 07 12.9:1 stock. so the JE high comp is not much higher than that being 13.5:1. now the 08 and 09's might have a stronger crank to cope but that is another story. thats kind of how i looked at it as, and it kind of calmed me down about the hole stress on the crank thing.

Share this post


Link to post
Share on other sites

couldn't tell ya. i am just saying that they might have differnt, updated cranks. but if you dont mind me asking.. where you located in pa

Share this post


Link to post
Share on other sites

08 nad 09 have different cranks, weighting is differnt is all, but the rods are the same.

The problem with a heavier piston is with hte rod not the crank.

The JE 13.5 runs quite well with west coast 91 octane, the crappiest of all gas.

Share this post


Link to post
Share on other sites

i heard the 13.5 was actually better on the crank/rod, due the the extra cousion of air the higher compression gives, is this true?, idk

Share this post


Link to post
Share on other sites
couldn't tell ya. i am just saying that they might have differnt, updated cranks. but if you dont mind me asking.. where you located in pa

harveys lake. like 25 mintues from wilkes barre

i ordered a JE 13.5 and kibble whites intake valve conversion kit. hope to get it running again soon.

Share this post


Link to post
Share on other sites

try using standard piston but with 04 head gasket . the head gasket is only 2 ply thick so works like fitting a high compresion piston . works good.

Share this post


Link to post
Share on other sites

the JE piston is actually lighter then the OEM piston... as for bottom end wear, there really isnt any extra wear with the high comp, the HC piston isnt going to make your motor take off like an F-16 but it will add a tad bit of bottom end

Share this post


Link to post
Share on other sites

thanks man, i am sure it will be fine for me. i had no real complaints with the power i had. is it garunteed that i am going to need to rejet?

Share this post


Link to post
Share on other sites
you shouldent have to rejet at all...

you will have to rejet to get the best possible results out of it..

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×