Ok thanks! I'll have to get a compression tester and check it

 

If it just died while running at full throttle, it could be electrical. If you sprayed starter fluid or primed it some other way and still no hint of kicking over, then I'd suspect electrical. First, replace the plug. Just because it sparks when you remove it and ground it against the block, doesn't mean it will spark under compression. It's a cheap thing to change out. Then second, check all you wires where they rub the frame. One could have worn through and is grounding out. Especially if it's the kill switch wire.

 

All the wires look ok, I was tapping on my valve cover and heard a light thunk from inside it, you think a valve was stuck?

 

I don't know. Does it run now?

 

is it possible your timing chain jumped a tooth. If you have good spark and fuel and all of a sudden it just shut down on you that is where I would go.

 

Yes. I hadn't thought of that. BUT, if the chain was still on the cam gear, even if it had jumped a tooth or 10, I would think that the engine would pop once in a while due to the fact that it would still be getting gas and spark and sooner or later, the gas would explode. OTOH, if the chain broke, then there would be no pop, ever.

 

It still doesn't run, but it does pop more of the exhaust, I didn't think the ex had a chain, but I don't know much about these atv engines

 

Have one timing chain on camshaft which works both rocker arms I would prolly check compression then see what its readings then if ok then remove value covers and get engine TDC an inspects values and rockers to see they are moving,If was running at high speed could have jump time or floated an value [bent] value or rocker nut came off, Then inspect TDC with cam timing and crank timing on flywheel to see if engine still in time

 

I am going to get a compression tester in the next couple of days to check it, being a eletric start only, it might be hard to get it tdc to check the timing.

 

It is very easy to find TDC. Your machine has inspection covers to view the timing marks and to manually turn the engine over using a socket and ratchet/breaker bar.