I posted a while back about my quad possibly jumping timing. Well, I am sure that is not the problem. I thought that it was fuel related because it would always start up after sitting for a while then just shut off. I replaced all the fuel lines,new filter, blew air in the shut off and reserve switch, and have taken the carb apart and cleaned twice, I even put on a brand new fuel pump thinking that may be it. The last time I put it back together it started right up and ran perfec for a few minutes, reved great, idled great, then started missing again and shut off. WTF? I tried running it with the choke 1/2 on and it ran really well, not perfect, but well, ran it for about 5 miniutes or so. Took the choke off and it fell on its face and shut off. I looked for a kinked line, found nothing. Is it possible the carb is just crap? I have never ran into such a thing. I have always been able to figure it out but this one has me stumped.

Jeff

 

Don't remember what you may have posted earlier,but you mentioned jumping time. Have you first checked the cam for damage to the exhaust lobe? Did you check the lower timing chain sprocket on the cranks shaft for damage to the woodruff key? Fresh fuel, carb diaphragm and slide ok? Plus you can do a compression test on the 500 even with the cam compression detent lever. Should be between 50-90 pounds compression. Plus is air box intact,no broken bolts on the box lid that could suck air? Have you checked the stator and pulse coil resistance? 90-115 ohms on the pulse coil White to White/Red, I think around 244 ohms on the source coil Red and Red/Black wires? Could be electrical breaking down?? Don't know if any of this might help. OPT

 

Opt,
Thanks for the info. I did check the chain and sprocket. All looks good. Rode it tonight for a bit. Is the fuel filter suppost to be full of fuel all the time? Mine is not. It will run pretty much normal with the choke lever 1/2 on. If I take the choke off it will run good for about 10 seconds before starting to fall on its face, then I put the choke 1/2 on and im off and running again. I just do not get it. I changed nothing to make it start to do this. It has 80psi on compression with the throttle off. So I tried it with the throttle at full and it went up to like 170psi. Is that normal? Sounds normal when running.

Jeff

 

Running good with choke half on is usually a sign of fuel problems still in the carb or fuel supply.Plus is the old style air box lid tight,no bolts broken off to where it's sucking air?. Did you replace the needle and seat when you went through the carb? Is there any blockage on the fuel inlet to the carb (can you blow throw it ok?). Are the main jet and pilot clean enough to where you can see through them? Fuel filter wont always be full since it's a vacuum operated system,plus did you check the vacuum hose going to the carb from the fuel pump for any damage ? Plus can also be a bad fuel valve itself stopping or reducing fuel flow. I've have had to replace them too. Pull the fuel line off the carb and try to crank,should be a pulse of fuel through the hose in reserve and in the on position. Could be this or even all the way back to the two filters and lines in the tank. Fuel has to travel from the tank to the pump, fuel valve then to the carb. Not normal to have that much compression on the 500 unless the cam exhaust detent lever spring is broken,slipped off,etc ,but check the fuel lines and fuel valve out first. OPT