My son has an 04 400z and the quad will just crank and crank without starting but if you roll it down a hill it will fire right over. It won't keep a low idle the adjuster nut needs to be turned up to stay running but when running the quad runs good.

Thanks

Stock quad? Will it idle fine with it turned up? How high do you have to turn it up? Does it start easier then as well? Maybe your just turning the idle down to low for the machine? No running problems at all other then that correct no backfiring or bogging?

I'm almost certain it's internals are stock it does have a Yosh Carbon pipe.

Yes it holds a good idle, but I would guess it is up around 2000-2500 rpms

It starts only when bumped over and will NOT start off the magic button, even if the motor is warmed up.

Again it runs great when it is running, this is whats throwing me for a loop.

Thanks again for the help.

Whats it sound like when it's cranking? Maybe that batterys not giving it enough juice?

You could be right but it will turn over all day, but maybe it doesn't spool it quick enough? but it even sat over the winter with no float charger and still cranks like it is fine..
It's an easy thing too check though.

no the problem is your valves are way out of adjustment. when you valves are that far out, there isn't enough compression for the motor to start by the wimpy starter motor, but when you push start it, the weight of the bike and the momentum forces the motor to crank at a higher rpm than the starter motor cranks. this also explains the idling problems. this is a very common problem on the crf250r dirtbikes that have alot of valve problems. get your valves checked/adjusted and it should fix the problem. you might need new intake valves, they are usually the first to cup. Im an MMI student so I've seen this problem alot. good luck - Matt

Yep valves out of spec, time to re shim.

Also check your cam chain tensioner to see how much is left clicks are left or how much chain has stretched, Almost certain if still original you will want to replace it while getting the maintenance done. I have a manual you can have cheap good idea to get one if you don't have.