1996 Sportsman 500 approx. 900 miles. Took out for a ride the other day and after running approx. 15 minutes while sitting still motor misses, backfires and stops and will not start. Got around to looking at it today, checked gas and appears good couple weeks old tried to start and with just start button just turns over will not start. Used full choke and fired up. Let it run for a couple minutes and turned choke off and kept running . Took for a drive 10-15 minutes and ran fine. Several minutes later started missing, I feathered the gas and kept running. Drove it wide open and kept running, tried to sit and idle and no problem. Wide open for several minutes and ran ok but did notice top end not quite as fast. Maybe 5 mph slower. Put carb cleaner in gas and ran a while wide open about the same speed maybe a little faster, continued to idle OK and no issues and put away hot. Any ideas what to check? Carb was cleaned and rebuilt 6 months or so ago and no problems till this, not sure where to start looking? Ideas please?

 

From your report it sounds like you might have some water in your fuel... try and drain it into a clear jar/container then hold it up to the light, if there is water you will see it trapped near the bottom. Can't siphon as the water will sit on the bottom, might try adding dry gas and see what happens. When it sucks gas it runs decent but when it sucks water they miss and run crappy if they run at all.

 

I pulled a quart from the bottom but did not see anything separating, thanks for the suggestion. I put some cleaner in that may help, will try it and see.

 

6 months may seem a short while ago but not if the fuel and carb wasn't protected. Stabil Marine,Startron,etc are good stabilizers along with keeping the battery on a tender. If you still have problems after using the cleaner you may have to go back into the carb,clean the jets,make sure you can see through them and make sure all passage ways are blown out. Doesn't take long for carbs to gunk up with ethanol fuel we get now days.

 

Will do. I took it back out today, it stopped once or twice but started right back up. I will get it back out and run newer gas and more cleaner. I think this will do it. Will let you know. I will also start the stabilizer as well from now on.

 

Gas can go bad quickly especially if your tank is not kept full. Many fuel stations run there tanks quite low, so getting poor fuel today is not uncommon. I use the blue Stabil, I have it for my boat but use it in all my toys. Only takes a small amount but it does help to keep fuel usable for a longer time. It helps to keep your tank full as well especially if your not using it on a regular basis.