engine mods

[bubba's400ex]

what is the best bang for the buck on a 400ex?

[xtullyx16]

exhuast.. sprockets.. rev box maybe... stuff like that! then comes pistons,cams, etc... but if u have a totally stock engine a slip on pipe is good enough.. u can also take off ur airbox lid or drill holes in it and when u get a pipe rejet it! and also an aftermarket filter would help 2!

[boricua]

from what i understand, the cdi box's main purpose is to raise the rpm limit. not really necessary unless your motor needs to rev that far.......
the after market pipe and filter will make a difference and is the cheapest, even though its not cheap. it will also get much louder.
2 pennies.

[RiderTRX400ex]

exhaust, filter, hotcam, REJET!

[Rossco307]

Honestly if you have already invested in a exhaust and CDI box and still arent satisfed you could go two routes, first being a After-market cam...which from previous experiance does give a good results , but when doing so you should also look into Beefer valves with titanium springs. If you can afford it a after-market Carb does wonders for a 4-stroke engine also but will cost you around 400 to 700 dollars. Many companys do offer stroker/ 440 kits for the 400EX, but well cost you a pretty penny.

[upyours]

personally i went with a 426 but i used to run a 416 an they run strong also i used to run a stage one hot cam and 12:1 copression with the duncan fat boy 4 exhaust and a white brothers cdi it was a strong motor and i ran and still run a 36 tooth rear sprocket give you more wheel speed then the stock 38 tooth and less wheelies out of corners but best bang for your buck without over boring would be cam exhaust filter cdi re jet and optional sprocket change you dont wanna up the compression over 11:1 with a stock cranck
and stock compression is 10:1 so you aint gonna gain much there with a piston change unless you big boring it

[upyours]

and you have to whatch what exhaust you run i used a white brothers e series and it didnt really do much except make it louder there really was no power gain so i went with the duncan pipe and it was like another animal

[GPracer2500]

Originally posted by upyours
...stock compression is 10:1...

Stock compression is 9.1:1.