O.k. I have had this 300 for a month now and I seem to be having to change the spark plug more than my underware. With a fresh plug every thing seems fine runs great no problems. After about 25 miles or so at full throttle it starts backfiring and missing, I change the plug and it's back to normal. I thought about jetts for the carb but it's not blowing black smoke and the exhaust temp is good. Could it be the jetts or not enough air? I have been using NGK DR7E plugs or what ever the manual calls for. The bike has no mods. Please help this is getting expinsive. Also the plugs I pull out don't realy look bad quiet black but no build up or corrosion.

 

I would say you need to change your jets, I think you need to go up a few sizes. I THINK!!! [img]i/expressions/face-icon-small-happy.gif[/img]

 

Thanks, But now I'm realy confused. If anything I thought I would need to go down a few sizes. I have read on the forums that AC overjetted on purpose to compinsate for cold weather. Plus if it was lean wouldn't the plug have a white crusty look from burning to hot.

 

Ah yes, maybe that is it, try going down a few sizes. [img]i/expressions/face-icon-small-happy.gif[/img]

 

If bike is stock you should not have to rejet. Be sure air filter is clean (if it is the paper style get a foam one). Also the 250 and 300 are bad about needing the valves adjusted more often it seems. I would check these out before I went to the trouble of rejetting. good Luck, TORK

 

It is the papper style. So what your saying is the resticted air flow is giving signs that it is over jetted making it run rich but realy its probaly jetted correctly just not getting enough air. Hey thanks alot. By the way what do you think about these K&N air filters.

 

I personally don't like the K&N filters but there are alot of people on here that use them. Your paper Arctic Cat filter is doing a good job but is hard to get cleaned out and causes restriction even when it looks clean. Start bike with air filter in and then pull filter out and see if you can detect a change. TORK

 

Would you suggest running the paper filter w/ out the foam sleeve. Or just change to a foam filter.

 

Change to foam filter. It is easier to clean and will help your problem. Running the paper without the foam precleaner won't change anything because it is the paper that is causing the restriction.

 

If you run the quad without a filter, it will run very poorly. And dont do it to long, you can burn a hole in your piston. There are mixed feelings on K&N. I have one and swear by it, in normal riding conditions. I alway have my stock filter on hand incase it gets dusty, and switch it out.