jetting question

[bcleveland]

A few months back I put a 450r carb on my 400. I have only put about 15 hours on it since this and have done several plug checks in the process. After changeing jets 5 or 6 times the plug started looking good light tan but real light tan. Yesterday I pulled the pipe off to do a little work and noticed inside the pipe and exhaust port were really light grey with a litlle bit of a chalky look. The valves were super light with a little touch of white chalk. This seems like to me the ole gorl is running lean. And on the verge of a burnt valve what do you think.

[JOHNDOE83]

You cant jet by looking at plug color, plug color only tells you pilot and needle jet, it also shows timing.

If your atv starts and idles, you dont really need to change the pilot jet, if your atv doesnt hesitate or stutter in the mid range rpms you dont need to change the needle.

The main jet is tuned by going large on main jet sizes until the atv stutters on the top end and doesnt fully rev out, then you back down jet sizes until it fully revs out. Only at this point will your main jet be correct in size.

In order to see main jet on a plug, you have to physically cut the threads off the plug after you do a plug run, thats why its called a plug chop.

You dont need to do that if you follow the directions above, it can also be found at www.jetsrus.com in the FAQ section.