I have a 1999 yamaha r1 that keeps fouling the spark plugs. it has been jetted, has a k&n air filter, d&dpipe?

ive been told serveral things, clean the carb, adjust the carb, get hotter plugs. the plugs that are in it are a 9, but i will have to find the heat range for the bike to get a hotter plug. im open for any other suggestions. just trying to get some more input before i take it to a shop.

Ah, the blind leading the blind! No. 1. NGK 9s are the correct plug. Champion plugs have a narrower heat range, will be more trouble. NGK - as good as you can get, going to an 8,(hotter) invites detonation, and preignition, neither do you want. Fix the problem by getting the fueling correct. No 2, This is a comon problem, and 99% of the time, it is not fixed by reducing main jet size. You get the main right first, THEN DO NOT CHANGE IT!!!!! Start at the top, work down. Any other way does not work, as you affect something else when you start from the bottom, and work up. Did you just change main jets, or do you have a jet kit, if so, the brand name? Actually, the Factory kit is the only one I have ever had consistent good results with. The others normally have needles which are way too small, which makes them very rich. , which is what causes the fouling. Stock needles,, with one or two small washers under them are normally best, give a bit more fuel, and in proper proportion to throttle opening, which needles with the smaller tapers do not do. Some bikes do like a different spring in the slide, but most run OK with the stock spring.

This is a quick rundown, I am willing to respond to E-mail questions if you need more help.

Tomcotexas Source(s): This is the stuff which I get paid for, for the last 52 years. I know it works.

go with a bigger coil and you'll get a hotter spark
If all plugs are fouling equally, you could put a next smaller size main jet in each carb. Be aware the #1 and #4 carbs might have different size jets than 2 and 3. Also I'm not sure if thats fuel-injected or not. If not, see if the needles have adjustable e-clips, then raise the clip up one notch on each needle.
Try ND or Champion plugs.
Check plugs for dirt residue.Dust could be getting by the side of the air filter.
me

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