Jet size and recommendations

[Veeger]

I need to find out what the stock jet sizes are for a 1979 XS1100sf. I have just installed a K&N inbox air filter and the plugs are burning pure white. What size jet(s) should I move up to, and which jets will have to be replaced? Any help will be appreciated. Everything is stock on the bike except for the K&N filter.

[trukleon]

jet sizes

HEY vEEGER, do a search and you'll find plenty of suggestions,, jet sizes should get you close..

[Ken Talbot]

Before you go into the jets, you might want to try resetting the float levels. I got an amazing effect on Tsunami by changing the float level by 2mm. It had been running way too rich - totally black plugs turned to a very nice light tan, all without changing the jets. You're going to end up taking off and replacing the carbs a half dozen times anyways before you're done - might as well start with this and see what it does for you.

[pggg]

Veeg, does the motor seem lean when cold ? Once warmed up does it respond a lot better? Are your sparkplugs brand new?

[Do Lee]

Hey Veeger,
I also use the K&N filter in the stock box but with a 4 into 1 Winning Preformance header. Stock jets are 137.5 mains and 42.5 pilots with the needle jet clip in position #3. After replaceing the the stock exhaust and air filter with the Preformance header and K&N filter I increased the main jets to 145's and left the pilots and clip location stock.
When I worked for Yamaha we would increase the main jet 1 or 2 sizes larger with intake modifications and 2 to 3 sizes with intake and exhaust modifications.