Carb synching... what the heck is the problem??

[hobbsy84]

No. Your carbs should have the plastic floats. The correct setting for the 80-81 carbs (BS34-III) is 23mm, upside down, bowl gasket removed. If you had 26mm, that is too lean. 26mm is the correct setting for the brass float (early) carbs.

Now, normally I'd agree with that, but for some queer reason, my bike has the earlier style carbs, brass floats and all. When I first got the bike, it made ordering a few things a bit difficult before I worked out what was going on. Try explaining to a poor unsuspecting high schooler at a sales desk that you own a 1981 XS1100, but why you're ordering parts for a 1978 XS1100...
Not really sure if that was a previous owner thing, or whether it came with them for some unknown reason. So I'm guessing in this case that 26mm would be the way to go?

[randy]

With an aftermarket muffler system and the UNI filter, I'd go one size up on the jets to the 140's you have spare. Worked well for me. Fine adjustments can then be made with the mixture screws. I just PM'd you about it.

[dbeardslee]

I replaced the plastic floats in '79 F carbs and set them to 25mm and they work well, but 26mm should work as well. Probably be and eensy bit leaner that way. Then again, some say 1mm makes a difference...

[79XS11F]

The carb synch should be the last thing you do in a tune-up. I'm a big advocate of colortunes - some people swear by 'em, others swear at 'em. I like them because it allows you to adjust the mixture by what's going on in the combustion chamber, not by number of turns on the mixture screws. Every one of my carbs is set to a different number of turns, but my pipes are all even colored and my plugs all look the same. The other thing you might check is your timing. I tried advancing mine a little, and Betsy didn't like it. Set it right dead on 10 degrees btdc (with the vacuum advance disconnected and plugged) and it made a big difference, even though it was only off a little. You've got the big guns lookin' at this one, but that's my $.02.

I also color tune and I would never go back to "seat of the pants" adjustments to my carbs. "Sometimes the truth is ugly, but it's still the truth" Color tuning tells the truth...
Rob

[Korr]

I think that someone here on the forums has a set of stock or tuned carbs that he will loan to members for cost of shipping.

[hobbsy84]

I think that someone here on the forums has a set of stock or tuned carbs that he will loan to members for cost of shipping.

I think the cost of getting a set of carbs shipped to Australia from the US would be a little extreme just to veryify I probably need to clean the set I already have... For that I'd probably be better shelling out for a brand new set of modern carbs to fit up to it. And thats not really on the cards at the moment.

[foreda]

Finding the answer

When you find the answer, let me know as I am having the same problem.

[79XS11F]

Get yourself a coffee can or other right sized container. 4 of them is best, 1 for each carb. Disassemble each carb without mixing up the parts. Put the body of the carb in the can intake side mouth down and add carb cleaner to the can to a level that is just under the shaft seals. Soak as necessary. After soaking turn them over so they are engine side mouth down and add more carb cleaner to the can to a level that is just under the shaft seals. add the other parts to each can and soak as necessary. Get yourself some spray paint gun cleaning brushes. They are very small. Use them in all the galleries along with spray carb cleaner. Follow with compressed air. If no compressor is available use computer cleaner air in a can. Clean all other surfaces with a tooth brush and rebuild with care.
My experience is that spray cleaning is ofter not enough. Brushes that make contact with the walls of the galleries is best.
Rob

[hobbsy84]

Might have to try and track down some of those brushes if I can, if it saves removing the carbs again I reckon it's worth it. That said, I went through the carbs today with spray cleaner and my air compressor, and as far as I can see, the galleries are allowing flow through the orifices it should (the three small ones in the throat too).
Did find a bit of crud in the pilot circuit in carb #1, and a bit of other spurious stuff that must have been missed last time. Other than what was in #1 though, nothing really out of the ordinary. Waiting for the air filter I ordered to come in, then I can give things a go. Will be sure to let you know if it solves the problem. Fingers, toes, arms and legs crossed.

[79XS11F]

That's the reason you need to run brushes through as many of the galleries as you can. The spray and or soaking will soften the crud up but not in all cases dislodge it so it will float off the walls in due time and plug things up causing trouble. Soak them, brush them, blow them and you should be good to go. After installation also run some sea foam through the system with first fill up of fresh gas and if not already in place use gas line filters.

Rob