07 trx400ex electrical problems

You dont have to buy a service manual. There are pdf.'s of it all over the net. Honestly to me it still sounds fuel related. I would take the gas cap off to be sure its venting properly. And i would also suggest pulling the screen that is down in the fuel inlet on the carb. Alot of people have no idea its there. Make sure its cleaned. Put the gas tank outlet hose into a gas tank and make sure you have steady fuel flow. It is possible its a coil or spark plug issue that only happens when you rev and it vibrates more than at idle. Welcome to the forums!

Start by removing the spark plug boot. Unscrew it from the wire and cut off about a 1/4 inch of the wire and screw it back on. If it was sparking at the wrong time it wouldnt start very good in the first place if at all. I would suspect ignition coil, cdi or some other electrical wiring issue. Does it do it in neutral and in gear with the clutch in?