400ex wont start-??

[pepshocks]

i bought a 400ex n the guy said it needed a new battery. it cranked fine but wouldnt fire. u put jump box on it n it fires right up. so i put new battery in it n does same thing until warm, then will fire up without jumpbox?? any ideas?

[drew416ex]

Does it have an aftermarket cdi? This is usually one of the problems associated with aftermarket cdi boxes.

[pepshocks]

Not sure I will have to check it out

[hocman123]

sounds like it still might have a 38 pilot jet my friend had 2 new quads that would never start untill we put larger pilot into it

[pepshocks]

Y would it start when u put booster pack on battery then?

[hocman123]

opps sorry its a bit late i didn't read it right

[drew416ex]

Because the aftermarket cdi's need the engine to turn over faster to get it to spark. Sometimes even a brand new battery won't do it. When you put the booster pack on it gives it that extra push it needs while it's cold. Not saying it is the problem for sure, but it sure sounds like the same problem I had.

[pepshocks]

Il try throwing another box on. Thanks for the info guys