differences betw 1979 & 1980 xs11 special carbs

[cabowabo]

Hi everyone,

New user.. I just bought a 1980 xs1100 sg and the original owner had put some 33 mikuni smooth bore carbs (non cv) on it. They are ok, but my old 700 maxim pulled as hard as this and being non cv, you have to roll on throttle slow.. I am going back to original carbs with dynojet kit but have heard of some differences between the years that you have to look for . Any help ..
Thanks
Mark

[John]

The 79 carbs are much more tunable than the 80's. Some of the internals are different, that's why the main jet sizes are different. The pilot circuit on the 79's is fed via the main jet, and the 80 has it's own circuit. That is the reason for the decrease in main jet sizes. The pilot screws on the 79 are adjustable, and the 80's are sealed for EPA pourposes. The 80's can be tweaked, but may be a little more involved. Either year will work, it just depends what you want to do with them.

[indyrick]

CV versus Smooth Bore

Hi Mark,

I've run 36mm Mikuni flat slide / smooth bore carbs on an XS11 and I can tell you that with the 36mm I lost a little on the bottom end but the bike pulled like a freight train in the mid/upper midrange (6000-8500). 33mm should have a little stronger bottom end with a sag on the top end due to the smaller throat dia.

One thing to look for (this is a guess of course) is a prev owner that was trying to increase his mileage. Because these carbs are different, you just have to experiment a little here. Check your jetting and increase the main jet and retest. Also, check the pilot jet and needle position as well.

If the low end is wrong, probably is a pilot jet / needle jet consideration.

These are guesses of course but smooth bore carbs work well on an XS

best of luck!

indy