engine question?

[jimmy7120]

Hey guys,
My buddy has a 400ex and he said the other day he was riding it and all of the sudden it made a sound similar to that of a gear-drive hot rod shutting down. (Never heard before so I dont have a clue!) And now when he tries to start it all it does is make a noise like the starter is spinning.

We have checked the teeth in the start, the gears in that side of the case, taken apart the top end, but everything seems fine in there to (valves, piston, cam chain seems wore out, adjuster is all the way out (prob needs replaced).

Anyone have any ideas?

[Thumper1220]

ok i have no idea what a gear drive hot hod sounds like...not even totally sure what it means but anyways. check the compression and the cam chain it's a good place to start

[jimmy7120]

if the motor is out of timing enough will the motor not start? It sounds like the starter is just spinning when he hits the start button.

We checked with the top of the motor off and the starter is turning the gears all the way to the cam.

Thanks for the response

[400exrider707]

So the cam chain is still spinning the cam gear then? That was my first thought. My next thought is it's jumped time. Since you already had the valve cover off, I would just check timing and go from there. It's a common issue, the stock chains stretch to unreal amounts, until the stock tensioner can no longer keep the chain tight. If it is the cam chain, replace it with an 02 CRF450 chain, it's the equivalent of a $100 HD one you would buy from DID or the likes, but it's only about $35, and still a lot cheaper than even a stock cam chain.

[jimmy7120]

yeah the cam chain was still spinning the cam. The tension was all the way out.

How do you check the timing on a 400? I assume it has to be at TDC on the compression stroke, but the book does not explain how to check the timing. Any help on this would be great!

Thanks guys for the replies.

[Thumper1220]

there might be a timing mark on the cam sprocket...not sure i have never been in the motor on a 400.

what i can tell you for sure is that when the piston is at TDC on the compression stroke all valves should be closed.

[jimmy7120]

that's what I was thinking. Thanks for the response