I have a 94 Polaris 300. It is a two stroke my son bought about five months ago. For three months it ran great. Now it will run for about 15 min then start loosing power and eventually will not idle and then dies. It will not start after that until the next day or after it sets for a long time. Then it does the same thing. I took off the carb and cleaned it very well. Still does the same thing. I am not very familliar with 2-strokes. What do I do next to fix it? Thanks for the help.
I changed the plug and same thing.

 

could be the spark coil getting hot after awhile,,,,,,,,,,,,,

 

run it until it gets warm and dies then check to see if it has spark.

 

Does that model have oil injection? When it dies - can you still turn the engine over, or is it stuck? It's possible you are "seizing" the engine due to lack off lubrication of the cylinder. You need to either mix 2-stroke oil with the gas or make sure your oil injection system has oil in the oil tank and is working. When the piston expands in the cylinder, it will expand and stick if it doesn't get oil to lubricate it. When it cools down, it will start/run again until it gets too hot. Just a possibility.

 

There is oil in the tank and it will turn over fine after it stops running.

 

If you still have spark after it shuts down check to make sure the fuel tank vent hose is not restricted,clogged or kinked. just a thought.

 

Good thought, easy way to check...next time you fire it up crack the gas cap loose. If it continues to run you know the tank vent is the issue.

Wenty

 

check your machines compression. sounds like your engine is loosing compression when it gets hot.

 

I'm not real familiar with 2 stroke atv's- but I had this issue with a 2 stroke husky saw (all 2 strokes are the same!)

Turned out to be the reed valves. When the valves were cold- they sealed, when they were hot- they would stay open causing poor running, lack of power, bogging down and constantly stalling. Replaced the reeds and presto- like a new saw!

 

polaris 300 motor doesnt have reed valves.