I have a 1999 Polaris Sportsman 500 4x4, it is a non HO and I have had it since it was new. My question is, Since it was new it has had a knock in the engine, it is only noticealbe when under load. Has any one else ever had this? Noticed this? Fixed this?

 

Have you had your valves checked?

 

Its a 1999, and the knock has been there since new,
Try premium fuel, compression ratio is 10.2 to 1, also use small amounts of carbon deposit cleaner in your fuel. If carbon has been building up since '99 the compression ratio might be higher now than when new. And Clean the air filter and put a new spark plug in.

good luck..............


handycap