I have a 2001 polaris scrambler 500 H.O. Sunday I went fourwheeling and throughout the day it started losing power (not right away ,gradually probably in a 4 hour time period). After a while it would not even spin in loose gravel t,rust me though that thing will spin like crazy when its running right it will ride a wheelie. But once I noticed how much power it had lost I became worried. It would run 20-25mph maxed out but the motor wasnt even buzzed up. As I was trying to get it home it really screwed up I could only hold it half open or it would start missing and backfireing like crazy. It also started spitting gas out the back out the carb. into the air box. I have know idea what it is. (checked fuel pump, timing, spark plug, clutches, water in gas, carb., and when I get off here I am going to check my valves).Does anyone have a timing mark picture? Back to the fourwheeler right now I can go down there start it up on first crank and it will purr like a kitten but once that throtle is over half way it starts its fit. Anyone ever have this problem if so please help.

 

This may sound stupid but have you changed or cleaned the air filter.My 500 does what yours did when the outerwear aka prefilter gets stopped up or a plugged vent line.Try running it with the gas cap off.If that doesnt work go to the valves the exhaust could be tight.Check the cam real good they do wear off lobes.

 

Thanks I will try that