Quadrunner dies and won't restart

I have a 1989 Suzuki Quadrunner LT250 4WD that starts OK, but then dies after it warms up and won't restart. It is cold here in Ohio and the colder it is, the longer it will stay running, which is about 15 min. If I wait a couple of hours and let it cool off, it will start. I have installed a new plug, and a new coil. Still no good. I have installed another new plug right after it dies and it still won't start. I remove the new plug and check it's condition and it seems dry. This model has a vacuum operated fuel pump. I have pulled the fuel line when it dies and I have fuel flow. Cleaned the air box filter. There is good compression after it dies. The plug I pull out when it dies is somewhat black with carbon. I have also drained the fuel and replaced with fresh fuel. I've also loosened the gas cap in case the vent was plugged. Any ideas would be appreciated. Thanks.

 

i would check the choke on your carb, it will cause this problem.when the bike is up to operating temp it will most likely dump too much fuel to the cylinder.check the plug when it dies if it is wet then i would suspect this..

 

I have the same machine and had the same problem. I found that gas was getting into my oil. In fact I had lots of gas in the oil. I replaced the needle and seat in the carb. This seemed to solve the problem of it running for a while and quitting Machine runs good but now I have to watch the oil level very closely. I may have polished the cylinder wall or the rings. This spring I am going to take a compression test and see what it says.
I live in Saskatchewan Canada. The last time I ran it was in mid Nov. and the temp was -15 C

 

sounds like it can be a choke problem as stated above. Does it just stall out or does it chug before it dies. any black smoke ??

 

I have a 1984 Quadrunner and it does the same thing, anyone have any help for me? Much needed and appreciated. Thank You.