xs1100 carbs

[mav2]

hi all hope someone outthere hassomeinput forme, ihave an 82 xj1100 i have a 79 xs1100 engine in it. i have changed the pickups to the xj pickups and the xj alternator, the carbs are off of the xs engine. i have completely rebuilt the carbs, new kits and hoursand hours cleaning the carbs inside.. all passages clear, new jets, floats all set to 25.6 mm. bench sync of carbs, put back on bike, ran bike and did vacum sync, all seemd to be fine, when i unhooked sync tool and put caps back on started bike and i have severe black smoke out of exhaust, no rpm ,trouble idling. and measured header temps 1=296, 2 = 300, 3=306, and 4= 112 degrees f checked for vacum leaks around boots and carbs, all good, anyone have any ideas as to where i can look next???

[Larrym]

Excitement

Gotta start somewhere but I'd start with simple.

Is the choke/enrichment lever in the closed or open position?

Are you sure that the vacuum lines which open the petcocks are connected at all the ends both at the carb boots and the petcocks?

Is the tank low on gas as in needing to turn the petcocks to reserve to get fuel?

Octy or no Octy and either way, would you bet $$$ that the lines are routed right?

Smoke out of both sides or just one of the pipes?


The best troubleshooting equipment is built right into your face. Start looking for something which you overlooked in the excitement of finally getting things ready for the road test.

[Ivan]

Black smoke indicates too much fuel. I would double check the float needles to see if they are hanging and over filling the bowls, since you were just in the carbs.

Since #4 is running much cooler than the others, suspect that cylinder. It is probably partially missing, meaning not a dead miss, but not burning all the fuel, and causing the black smoke. Pull the plug on that cylinder and make sure it isn't fuel fouled.

Report back on what you find, and we can go from there.

[mav2]

carbs

well, as far as the petcocks, the bike had an octy, but i removed that. so no vacum lines to worry about there, and the tank is still off the bike on a stand, and i checked both fuel lines before hooking them to the bike i have fuel on both. as faras smoke goes, only have 1 pike, it is a mac 4 into 1 exhaustsystem, the bike seems as if it is running way too rich, maybe i have my floats set too high?? what ya think?

[Larrym]

square one

If in fact the bike ran "well" when the gauges were connected and now that the gauges are removed it's running like cr*p then something is different between those two setups.

If you set it up just like it was when you were synching the carbs and it runs well then the problem should be with what you did differently. If it still runs like cr*p when you repeat the original sync setup exactly then something else has happened.

Decision point here:

Is it something new going on or is it something different between the setups?

Nobody would want to go back to square one but that would tend to rule out one possibility or the other. "Introduce one change at a time and see what the result is...."


Do you place fans around the motor to keep air flowing and the the engine cool?

[mav2]

carbs

i haven't gonebackand set up the sync again yet, and no ididn'thave fans aroundthe engine while i was syncing, but was keeping an eye on the temp..
the other thing i am wondering is ifthe float setting for the xs is different then that of the xj, because the engine is running with xj electronics, anyone have the answer?

[DGXSER]

If you have the old style 79 carbs then you need to se the carb up for what it is regardless of the year fo the engine or the machine. So you should find the stock float level for the 79 carbs which I believe is 25.7mm IIRC.

[Larrym]

Nothing special

Are you saying the carbs are for the later XJ model but mounted on an Earlier 79 engine?

Pretty much irrelevant as far as a mismatch. XJ and XS carbs don't require any special settings when you swap the electronics. IMHO

Just make sure that you set the carbs according to what they are. The engine really doesn't care as long as they do their job

[mav2]

carbs

the bike is an 82 xj, the engine is from a 79 xs1100sf, and the carbs are the carbs off of the xs1100, i didn't buy them with the engine, but went back the next day and bought them..float height is set at 25.68 mm now,and i did check that both sides of the float were the same, and all 4 carbs are set the same unless i measured from the wrong point, i measured fron the flat gasket area of the carb to the highest pointof the actual round float..

[Larrym]

Addendum

Really is frustrating sometimes when you're so close to putting the bike back on the road and then something sends you back to the G'rage.

I built a test bank of carbs to isolate exactly what the deal is in situations like these. I'm even considering putting them up as available to the members for troubleshooting purposes. Unfortunately they're jetted for an unmodified bike and might not help you out here, Mav2.

Gotta bail for now as the real world "to do" list is calling.

Keep looking. You'll know it when you see it.

Will check in later!

[DGXSER]

Also measure with the gasket removed, although that would only richen the mixture up. Take the bottom off the air box and open the petcocks to make sure your not flooding with a stuck float needle?? JAT

[mav2]

carbs

did another check this evening, and what i have discovered is that cyl's 1 and 4 are not firing all the time, now i have brand new dyna coils in there, so i suspect istill have an issue with my igniter, ihave already resoldered several bad joints on the board, guess i will have to do the entire board..any ideas?

[DGXSER]

JAT, did you eliminate the vacuum advance and the mechanical advance form the 79 engine? The XJ model did nto have either and the TCI was setup without them. I have learned that the engine will work ok either way, but it may be effecting your setup. The TCI could also be the issue, if it has had problems in the past, I would think you would rework it.

[Geezer]

Pull all the pilot jets and look in the small end. If the tiny opening is at the end, this isn't the problem but if the metering hole is toward the big end of the jet, you have the later model jets that don't work right in our carbs. The later pilot jets in XS carbs will do exactly what you describe.

The funny thing is the old and new type jets look about the same from the side but only really look different when you look at the small end...

Geezer

[tw1980]

Like Ivan said if it's smoking you have to much fuel.(unless you're burning oil)If you didn't have this problem before you rebuilt the carbs I would recheck them.I know it's a pain but so is looking for the problem in the wrong place.My guess is you have a stuck float valve.I don't see how disconnecting the vacuum gauges could cause a problem Good luck.

Terry