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1980 XS 1100 SG Carb Woes
Hi Everybody, I'm new to this forum, but not to motorcycling! A little bit about myself, I'm 49 now I've been riding and wrenching on bikes since the age of 12. I currently have about 45 bikes. I can't seem to pass on a good deal on a motorcycle! I have a great (and understanding) wife and two daughters, a dog and 2 cats. I work for G.M. Powertrain in Flint, MI where we build SUV motors. I have a little 32X48 garage where I work on my bikes. I bought a '80 XS 1100 SG from a friend who also works on bikes, this bike was a customers who wanted the carb intake boots replaced and the carbs set. Gary (my friend) did the work and the guy never picked the bike up, so it sat outside for about a year. Then I saw it and had to have it, I paid the bill on it and it was mine! I brought it home and it sat for a while longer. I finally got around to fixing it, I painted it Torch Red and recovered the seat new tires and polished all the aluminim parts, I put MAC four into two turnouts on it, and I cleaned the carbs. I generally brought it back from the near dead, It look fantastic! The bike would miss and sputter when cold but when it warmed up it would run fine. I noticed that # 3 and 4 pipes looked like those cylinders were lean (blue pipes). I sold the bike to a local minister who rode it for about 1500 miles, He brought it back late in the fall complaning that it no longer ran right and the carbs were leaking. Well this is where my nightmare begins... I have a Yamaha service manual for the '79 XS 1100 model I realize that the carbs are different but are the adjustments different? I've checked the timing and set it (it was off), The compression is #1 112, #2 112, #3 110, #4 120. I readjusted the valve clearence to specs, checked and adjusted timing chain, I checked the mechanical advance and the vacuum advance both working and in spec. I've had the carbs off this bike countless times, I bought kits for it, The carbs had 110 mains across the board and 42.5 pilot jets. So I put the kit jets in now it had 120's across the board, the pilots remain the same. I initially set the floats at about 22mm It was rich! so I reset them at 23mm It would run but when I revved it it would stay at about 2500 rpm and then drift to 1000 rpm then it would idle there for a minute then die. I set the idle higher but it would just run at 3000rpm then float to 1000rpm then die. I tried the pilot screws they are set at 1.5 turns if I turned them out to say 2 or 2.5 it wouldn't make a difference but if you turned them out to 3 you could tell it was too rich. When cold it would start right up and run fine (that's when I synched the carbs, 8 inches of vacuum across the board). I've now set the float level at 25mm and put the 110 mains back in it, at this setting the tang is bent so far down that the needle will fall off if you don't hold it when you put it in the seat. Now It backfires and won't idle at all, it dies. I would like to know what the difinitive setting for the float height should be, What kind if vacuum should I have, What is a normal setting for the pilot screws, Should I have richer mains for the two middle cylinders? All tests were preformed with the airbox off because at idle it shouldn't matter, And like I said I've had these carbs off this bike so many times that now all I have to do is snap my fingers and they fall on my bench!! Any help will be greatly appreciated.
Scott.
Scott.
Okay, first, there has recently been some controversy as to the presense or absense of the fuel supply tunnel between the pilot jet and main jet tower in the 80 circa models! The 78-79's have this tunnel cause the pilot gets metered thru the MAINS, hence their larger 137.5 size. With the 80-81 series carbs, that tunnel is NOT supposed to be there, and the pilot gets metered straight from the bowl, so it should NOT have a rubber plug over it! You say you kept the pilots the same, HOWEVER, the other mech worked on the carbs first, and so you can't truly verify that he used OEM Mikun pilots vs. the K&L which are notorious for being OFF....too rich for the stated SAME SIZE!!
,
A few taps with a hammer on the bowl during the ride sorta helped it get unstuck! I've since repaired it, and now it behaves very well thru the entire rpm range. 
Freddie Mercury that is/was! Sad he had to leave us! 
From their Night at the Opera.....I'm in love with my car!! Funny, I was going to post that to the Yahoo groups Friday Night music trivia they like to post!
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