Only Running On 2 Cylinders

[shortyno10]

i have a '80 xs1100 and it has been sitting for 10+ years and i have been workin on it for a couple months and got it running a few weeks back and i noticed at idle it only runs on the right 2 cylinders. its not till i hit half throttle the other 2 kick in. is there a jet i need to replace? ive cleaned them a few times already. i dont know what to do. please help, its driving me nuts.

[pggg]

Shorty, there ain't no easy way out, electrics are a nightmare and carbs are another nightmare, running on two cylinders and kicking in to 4 cylinders at higher revs, you're lookin' at either one or the other or both combined probably with other factors involved as well, I wouldn't like to be in your shoes but there may be a slight chance of someone on this website knowing the quick fix

[shortyno10]

yeah it sucks balls. i know for sure their getting spark, but i just dont know why they arent running at idle.

[mro]

enricher/idle circut not working on one and two...
off with the carbs...agin
pilot needle (fuel air mix screw) needs to be removed to clean that portion of the "low" rpm circut. If the caps/plugs still cover the screws they will need to be removed to get to the pilot needle.

Also there's a fuel jet in the carb bowl that seems to get over looked when cleaning carbs.

Could be something else but most likley above...


mro

[shortyno10]

i will try that and see what happenes. thanks for all the help.

[prometheus578]

"I agree with MRO."

( He pays me to say that)

[wingnut]

Could the sync be that far off?

[mro]

money well spent

( He pays me to say that)

you told me you wouldn't tell


mro

originally posted by wingnut
Could the sync be that far off?

has no effect on idle
needles start to lift aboce 2,000 rpm

[TopCatGr58]

Yeah, vacuum leaks do suck!

Hey Shorty,

I, too, concur with MRO, and my opinion is totally unsolicited, at no cost.

The problem you stated was a pair of carbs, linked by a common fuel supply, the right 2 carbs, #'s 3 and 4. IF it was ignition, it would be either 1-4 or 2-3 paired carbs. They start hitting when you open the throttle, so fuel IS getting to the carbs, and thru the mains, but the pilot circuit is most likely clogged. You didn't state what you did when you cleaned them, but you HAVE TO take the jets out to properly clean them, not just spritzing carb cleaner into the bowls!

A search for pilot jet caps will reveal threads on the removal procedure!

Also, BEFORE you remove the carbs, check for vacuum leaks around the intake boots. Folks have found the rubber synch port caps harden, and even though they are on the port tube, they are slightly loose and will leak! Easy replacements are available from Auto store, or homemade! Also check where the boots mount to the engine. Folks have also reported just enough of a vacuum leak to prevent the pilot circuit from being able to draw the fuel thru it, but once the revs are up a bit, there is enough air flow to activate the mains!

Just don't SOAK the carb bodies in a bucket, or you'll most likely damage the butterfly shaft seals causing yet another vacuum leak source!
T.C.

[shortyno10]

ok. so i replaced the mixture screws and cleaned all the jets in the first 2 carbs. i put the carbs back on the bike and now only the first 2 cylinders are running instead of the last 2. so now its reversed. so i guess i will do the same to the other 2 and see what happenes.

[LoHo]

Did you check for free flow from the tank? I chased a carb problem for a while once before I noticed that one petcock didn't leak a drop after I pulled the hoses. The hose had delaminated and blocked fuel flow...all of it, on one side. New hoses, no more "carb" problems...

[LoHo]

Duplicate post...
Took care of it for you, with a magic marker....
DiverRay