So me and my dad are about to pick up this sweet trx400ex its a 2004 and its been built a little. It was bored 40 over has aftermarket cams and some other things. But the problem is the guy said his brother was riding it and all of a sudden it died on him he tryed starting and it wouldnt start back up. He said he took it to a shop and they said it needs a new flywheel but i dont see how that would of caused the motor to die. We got him down to 1500 for it. do you think its worth it or could there be other problems with the quad.

Josh142, on 12 July 2012 - 12:38 PM, said:

Flywheel rotates around the stator and creates spark. Perfectly good reason as to why it died. Take off the flywheel cover and check everything out. Make sure it didn't eat the stator also....

Ya that wasnt the problem the timing chain came off. We put it back on and tried to start it but the motor just kept turning over the flywheel looks fine and so do the stator. Maybe valves could of got messed up when the timing chain came off?

Do you have a compression tester? If you don't I suggest you get one and test the compression. That'd be the easiest way to figure out if something in the top end is bad.

make sure you line the timing up right the cam lobes should be facing the rear of the bike andf there should be two little marks on the cam that should be level with the case......if you dont BOOM also i would get a new cam chain tell me how it goes

and you can always do a leak down test on the valves get some solvent and put it in the head (off the bike) and see if any solvent comes through the valves

Well me and my dad took the head off and the valves were completly bent and werent closing so we just bought a pretty new looking head that came with valves and everything. Also we figured out the reason the timing chain came off was because the tensioner broke and wasnt tightening the chain but we bought a manual adjusting one instead of the stock one. Looking to start it up this weekend and taking it for a ride next week, pretty good deal if you ask me the guy we bought it from paid 4000 for it in march and we bought it for 1300 and only put about 400 in it.