95 Bayou 300 4x4
 

This quad was given to me from a friend at work. It ran when he used it last but hasn't been run in a couple years. First thing I did was to clean the carb, although I never seem to get a carb cleaned the first try. Reinstalled the carb and it would turn over about 4 revolutions and pop the carb off from the boot. I did some research and found out the valves should be adjusted. Adjusted the valves and installed a new spark plug and it runs, idles nice but boggs out and stalls at anything over 1/2 throttle. Also noticed a pretty good blow back coming from back out of the carb. It will run for 10 minutes and then stalls out. If I put a rag over the carb I can get it to start again as long as I let just a little amount of air in. Checked the valves again and put the air compressor on the compression tester lead and could hear a little air coming from the valve cover area, but nothing distinct from the exhaust or carb. Then I did a compression test after that and was at 90. Am I chasing to many things? Is it a carb issue or something in the head? What should be my next step...
Thanks
Bman

If it now runs OK apart from over half throttle, you probably didn't get the carb right first time. Does it run better on choke? Because they have car style DC ignition, battery and charging problems can cause upsets. It is worth checking voltage across battery with engine running, should be 13v to 14.5v

Checked voltage on the battery before starting 12 volts. Starts up idles for about 2 minutes fine then it dies. Voltage on battery stayed at 12 volts while running. Thoughts....

Did you not try revving up when testing battery voltage? If voltage didn't rise, sounds like you have a problem there, but it is overcharging (above 15v) that upsets ignition boxes. Un-plug the voltage regulator, in case it is taking all the battery power, and check if the bike then runs right. However, this is unlikely to be your problem, which is still probably carb related, if it isn't the regulator, check that carb again.

Update... Still not perfect. I figured out the issue with it running and then staling, petcock was plugged in the on position,it would flow a little as I turned it on but then would stop. Still idles great but has no power. I pulled the head off and looked it over and was expecting to see something but everything looked good to my eyes. Put it back together and the timing mark seemed a little behind the mark, so I moved the timing one tooth. Put it back together and it would barley run. I moved it back to the original positon and it still idles good. A buddy stopped over and was asking about it, I explained what was going on and we started it, he thought maybe my exhaust was plugged. While it was running he put his hand over the exhaust to block it completly but it kept running. Not very long, he thought that was odd. He said that maybe my cam was worn down. I went to the exhaust and loosened the valve and tried it again and it turned over a couple of times and poped the carb off from the boot again. Is it something in my head or timing?

Bman

Did you check the piston ring gaps when you had the head off? Have you done a compression test? The cam can wear badly on the 300, but can be checked when you have the head off, did you check it?