440 hard to start when hot

[jimmy3fan]

i have a 2001 400ex with a 440 kit with 12:5:1 compression with stage 2 hot cam and rev limiter box and i was told that i needed to take the decompression off and not put it on the stage 2 cam and i got the quad running and it runs great but when shut it off it wont start back up untill it sits for like 30 minutes then it starts right up and does the same thing over.

[F-16Guy]

If you have one of the White Brothers style CDI's (smaller than the stock one; actually an XR250 bike CDI), it could give you starting problems. Those CDI's won't allow spark unless the engine turns over above a certain RPM. That is because on an XR250, it prevents the kickstarter from whapping you in the leg when you kick it over slowly. It could also be overly rich jetting. When the bike is cooler, the air going into the intake is cooler and more dense, effectively giving you more air for a given amount of fuel. When the engine is really hot, the air is less dense, thus creating a richer mixture. That is why you have a choke; to compensate for the colder air by adding fuel. Do you know what jetting you have right now? Does it blow black smoke when you stab the throttle or accelerate hard? I think it's probably the CDI, but I guess it could be either if the jetting's way off.

[cals400ex]

normally the CDI would make it harder to start when it is cold, not hot. that is what i have experienced anyways. is your battery low? when our bikes are hot the battery cranks slower sometimes, plus you do have high compression for a 400ex. yes, you want that spring and plunger out of the head with a hotcam. what is your jetting?

[Kaleigh]

im thinkin its the battery.. how old is the battery.. has it died on you before and you recharged it??