What are you running "IN" your 300ex's

[Sjorge450R]

Well, its time for a new piston and rings and i am leaning towards a wiseco 11:1 (not sure on the bore yet, mabey up two sizes). I am just wondering what you guys are doing to your engines. I am new with 4 stroke and I need all the help I can get.

[hardkoratvmxr]

get 80 over and 11.1 compression that will put you at 297cc (true 300) and you cant still run pump gas

[stc416rider]

i would go with je

they r better quality

[rooster300ex]

If i was you get a FST 330 kit. I wish i would have, by the end i had spent almost as much on rebuilding it back to stock bore then i would have making it a big bore 330ex. its worth it in the long run.

[Sjorge450R]

i am racing and it has to stay under 300cc.

[Cody_300ex]

Originally posted by rooster300ex
If i was you get a FST 330 kit. I wish i would have, by the end i had spent almost as much on rebuilding it back to stock bore then i would have making it a big bore 330ex. its worth it in the long run.

When you get to much bigger than a .080 piston you really need to port the head a whole lot, get bigger valves, bigger carb, ect or you wont get to much more power out of it than a 297 kit. SO i would suggest just staying with the .080 11:1 compression. If it were me i would go with weisco also.

[Sjorge450R]

i know i asked this before but i have yet to get a clear answer. Someone told me that I need to replace the vavles too. Is this true?

[rollie]

im running... .80 piston with 12:1 comp ratio and a .335 webcam with hardened rocker arms....i having a ahop do it and im getting it back teusday...ill tell you have it is then:D

[2muchquad]

385cc kit ,wb cam(1850),11.5 to 1 comp piston.modified supertrapp exhaust with custom headpipe.ported head with only a slight cleanup on the intake side(keeping velocity up is where you make your money),about 3 hours of gring and polishing on the exhaust side.if i cant get it to run right with a keihin pwk series carb then ill just go with my 400ex carb.:)

[Cody_300ex]

Originally posted by Sjorge300EX
i know i asked this before but i have yet to get a clear answer. Someone told me that I need to replace the vavles too. Is this true?

NO, you dont.

[Sjorge450R]

Originally posted by Sjorge300EX
i am racing and it has to stay under 300cc.

Lil 300ex, you seem to be the only one helping my out. I am just going to go ahead and get a 11:1 Wiseco and lator decide on the bore. Is it going to be a noticable different going to a true 300. Also what happens if I score the head then what do it do? What is the size below 297?

[kyleschonert]

If your not racing anywhere that is AMA sanctioned you should be able to run as high bore as you want. If you can, get the 330 kit. And yes, you will see a big differnce going to a true 300.

[Sjorge450R]

i am racing 91-200 2str 91-300 4 str. I have to stay under 300.l

[hardkoratvmxr]

yopu will defantely see noticeable gains with 11.1 80 over piston

[Honda TRX250ex]

my brother 300ex went from being stock to 40 over in one bore!

[Cody_300ex]

You wont score the head, well unless you keep running 10 year old intake valves on a built engine like I did, then you end up breaking them then you will score the head. You will also notice quite a difference in power. I noticed quite a bit just with a .040 wesico 11:1. I would also reccomend getting a 400ex carb, you can get them for dirt cheap (40-75 dollars). This is the result of two broken intake valves. PS this picture does no justice, i just have a chitty camera.

[Sjorge450R]

what all do i need to make the 400ex carb work?

[Cody_300ex]

A 350x airboot.

[300ex mxracer]

dont have to have a 350x airboot, i dont :devil: