400ex hard to start

[lillbro11]

I have an 03' 400ex with a curtis sparks exhaust, 11:1 compression piston, k&n intake, 152 and 42 jets, and a shindengen cdi box.

I have been reading that its the cdi box that causes the weak spark and the hard start. Its about an inch or so shorter than the stock one. I put it on a friends bike and he had trouble starting his.

If this is the problem what cdi should I buy?

[EXinMB]

i put a 12.5:1 440cc piston in mine and its hard to start with a stock cdi. I had an aftermarket one and ya it wouldn't do anything i had to pull it with another quad to get it to fire. i put the stock one on and now it works fine. just hard to start cuz of the compression my starter can't spin over fast enough

[lillbro11]

it was the same before the 11:1 piston

[aDviSol2y]

I have a BigGun and mine is never hard to start. Fires right up, every time.

[raptor660103]

check ur valve. make sure they are in spec. just a thought