Possible to swap carb bank from 78 t0 80?

[westpat]

Hello,
I am new to this forum, thanks for allowing me to register in light of the issues.
I have an 80 xs11Special and a 78 xs11.
I took the carbs off of the 80 to clean and reassemble. I have had good luck with that, but I am entering new territory with synching 4 carbs. My questions is, can I transplant the carbs off of the smooth running 78, in need of new tires, to the 80? everything else on the 80 is really pristine and I would like to be riding it while I bring the 78 up to speed. I know this would be cheating, but I would have one bike to enjoy while taking the time to fix the other.
Is this even a possibility, and is this a wise thing to do?
All guidance is appreciated, my feelings won't get hurt.
Thanks for your time,
David

[DiverRay]

Yes, they will go in and work fine. The problem is you will STILL need to sync them to have it run correctly. each engine is a little different, and they can change over time. that is why you need to sync carbs. Part of the sync is adjusting the idle mixture which WILL be different for each engine.
Welcome to the site!!

[westpat]

Awesome,
I would feel so much better about being able to enjoy one right now.
I have the vacuum gauges and my son and I now have our weekend project lined up!
David

[TopCatGr58]

Hey Pat,

Just remember, don't change the jets!!! The jets are set for the year/model style of CARB body, not the year/model of bike. The 78 will have larger mains than the 80's, along with a variety of other differences, but they will not matter...they(78) carbs are jetted properly for their carb bodies. As stated by Scott, you will just need to tweak the fine tuning aspects...pilot screws and vac. synch.

Also remember that the 78's upper T's are VENT ports, and need to be open to vent...not plugged or capped....they are usually piped into the airbox nipples which are vac. ports to help recycle fuel vapors as well as allowing air to let the float bowl chambers vent. The 80'81 carbs have the bowl vents built into the intake/inlet bell...that's why there are 4 small ports vs. only 3 on the 78. If you have the airbox on the 80, check the nipples, they are probably PLUGGED because their carbs didn't need them, and Yamaha just left the nipples in the mold, but sealed the opening on the inside of the airbox.

If you cap the vents, the carbs will flood and leak!!!!

T.C.

[DiverRay]

Thanks, T.C., I forgot about that! Put a fuel filter on each VENT hose, and call it good. The airbox has a brass fitting inside the plastic that you would need to install, so don't bother. The other way is take the airbox off the '78, and use it on the '80. It should be a bolt on, as the ONLY difference is the vents....

[westpat]

Will definitely do that, since both airboxes are in equally good shape. I will just swap them out. Thanks for the insight and quick response.
David

[BowlingSS]

Good luck with the carb swap. I did not know that the carbs would interchange without changing any thing.

Bill

[Bikes]

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