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Time for a rebuild
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Posted by: AtvMxRider

Well it's time for a top end rebuild on my 400. I plan on going up to a 416. What compression ratio should I run? Any particular piston brand? Any help would be appreciated

Posted by: trx400EXtreme

ive always heard good things about JE pistons. wiseco are good too but ive heardd people say stay away from them. as for compression im not sure.

Posted by: AtvMxRider

I have always had good luck with Wiseco pistons on 2 strokes. This will be my 1st 4 stroke top end.

Posted by: nickk

I got a 416 with a JE 11:1 and a stage 2 hotcam and I love it .... pulls so much harder then stock.. I would also recommend a crf 450 timing chain ... I didn't put one in at first and the stocker snapped so I had to tear it all apart again and put that in and it runs awesome no problems whatsoever... and it will still run off of 93.

Posted by: Ruby Soho

i think JE and wiseco are manufactured by the same people.. but anyway

go with 11:1 CP, you can still run pump gas and not worry about a rod breaking. i would also throw in a stage2 hotcam along with a CRF450 cam chain. and if its a 416 just to stay on the safe side, put in the hd studs it can't hurt, only help.

Posted by: wvspeedfreak

Jerry,that 400ex that I had a couple years ago(the one cletusEx had) was a 416.It had an 11:1 JE piston and a Web Cams 450/451 grind cam.That thing ran better than any 400ex I have ridden.Whenever my current 400ex needs a top end,that is what it is getting.

Posted by: mitchamus

Not sure if this is true but something to check out if you buy a wesico. Whenever wiseco offers a piston for the 400ex engine they base their compression ratios off the XR engine. Example- If they say its an 11:1 piston its really going to be a 10.8:1 compression. To fix that problem you can put on a XR headgasket and that will bring it back up to the true compression ratio due to the 400ex having a thicker headgasket.