Before I turn too many wrenches I think I'm going to run to the dealer & get a new spark plug & air filter. Service manual said air filter should be changed once a year and I've never done it. (Had the SP 400 since Dec. of '04) On the spark plug my service manual says the following for what plug to use:

Under "General Infoormation"
SP 400 - NGK BKR5E
SP 500 - NGK BKR6E

Under "Maintenance" it list NGK BKR5E and is referring to both the 400 & 500.

Any idea which is right? I'm going to replace the air filter & spark plug on our 2005 SP 500 also.

 

I stopped at the dealer and picked up $50 in parts for our 2 ATV's (2 fuel filters, 2 spark plugs, 2 air filters) and I also talked to the mechanic there and he said since I'm at 200 hours he suggested a valve adjustment (which is really supposed to be checked every 100 hrs according to the book). He said if the valves are out of adjustment this may be the problem. I'm dropping it off on Thurs. and he'll adjust the valves for 2 hrs. labor ($140) and a new valve cover seal. Hope this does it!

 

Mine is fixed! I was impatient so I'm not sure what fixed it but I think the biggest improvement was from the Dyno Jet. I also moved the driven clutch spring to setting 1/1 and intsalled a K&N filter. It runs pretty good now. I guess I can wait on the 800...