PLEASE HELP! quad pops and cracks after a minute of riding and wont take throttle

[Jake250ex]

I just traded my 07 for a built 04 R.

it has a HC stg 2, 13.5:1 JE, ported head, hmf slip on, no airbox and a 180 main jet...

It RIPS - for about 2 minutes. Then pops and cracks so bad it wont get out of its own way. The 1st day i got it it was almost impossible to start and doing the same thing. So I checked the timing and it was waayyyy off. Idk how it even ran. So I set the timing. It starts 1st kick now and still runs strong for a minute then cuts out and falls on its face.

I have -

put new fuel in
cleaned the carb
adjusted the valves
set the timing
put a new plug in

Im thinkin it has to be electrical. Im not sure where else to look.

Any suggestions?

[Scro]

Make sure the gas cap vent is not clogged.

[honda400-4-ever]

fuse? samething happened on my 400ex

[Scro]

If it was the fuse, he would have to replace the fuse after it died. His symptoms are very close to what happens when the gas vent is clogged. The carb will run on whats left in the float (couple minutes), but can't get anymore from the tank because of the vent being clogged.

[JParisi48]

do u have a hot start that works, if not check the plug on the carb, thats the same thing that happened to my cousins, get a plug if thats it and ur problem should be fixed...i suck at this stuff so its just a guess but its worth a try...

[Scro]

What was I reading? :o I could have swore I read that it was dying. Disregard my posts.:o

[ppeengines]

Did you take the exhaust off? If you did did you replace the copper crush ring/gasket when you put it back on. This will cause your your engine to back fire and run poorly. You said the timing was off. Maybe needs a new timing chain and tensioner. Or it can be you need a new coil and cap. Its hard to figure it out without being right there when the quad starts acting up.