Size 100 jets?!?!

[deanstrickland]

Hey guys I am rehauling my carburetors as the bike hasnt been running quite right. Bogging down and such. Ive carb synced, colortune on the way.

Can anyone explain to me why I might find size 100 main jets and size 25 pilot jets in this carb? I understand 110 and 42.5 are the specs. PO trying to lean it right out? I replaced the mains with 117.5 as per the recommendations but it ran far too rich. Went down to 112.5. Ive measured float level at 23mm, cleaned the carbs, fiddled with mixture. Lots of backfiring.

Current setup:
1980 xs1100 s
dynacoil
Octy delete
2 to 1 pipes
pods

[DiverRay]

Are you using Mikuni jets? If not, that is problem #1 You probably need to "bench test" the carbs somehow. Sounds like something isn't correct, or maybe you have a bad seal in the needle seat, and are leaking gas into the carbs.

[cajun31]

Hey guys I am rehauling my carburetors as the bike hasnt been running quite right. Bogging down and such. Ive carb synced, colortune on the way.

Can anyone explain to me why I might find size 100 main jets and size 25 pilot jets in this carb? I understand 110 and 42.5 are the specs. PO trying to lean it right out? I replaced the mains with 117.5 as per the recommendations but it ran far too rich. Went down to 112.5. Ive measured float level at 23mm, cleaned the carbs, fiddled with mixture. Lots of backfiring.

Current setup:
1980 xs1100 s
dynacoil
Octy delete
2 to 1 pipes
pods

ditto on what Ray said concerning the jets. How many turns out are you on the pilot screws? Backfiring is and indication of they are probably way off. When you were in the carbs did you bench synch them. There is a tip concerning using a bread tie to accomplish that. I start there and always start with the pilot screws 2 1/2 turns out from lightly seated. You stated you are at 112.5 mains but did not say what size pilot jets?

[deanstrickland]

cajun31 I bench synched with a feeler gauge after using my vacuum gauge and they were all the same.ive got my mixture screws out 2 turns with 100 mains and apparently size 25 pilots. Idles fine right now, going to put a load on it tonight.

DiverRay they are in fact mikuni which is concerning why I found the 100 mains and 25s in there. It seems to idle fine now that ive put them back in, ill see about the load tonight.

[cajun31]

cajun31 I bench synched with a feeler gauge after using my vacuum gauge and they were all the same.ive got my mixture screws out 2 turns with 100 mains and apparently size 25 pilots. Idles fine right now, going to put a load on it tonight.

DiverRay they are in fact mikuni which is concerning why I found the 100 mains and 25s in there. It seems to idle fine now that ive put them back in, ill see about the load tonight.

You are running way too lean with those jets. you should replace with genuine Mikuni... 42.5 pilots and 110 to 115 mains.

[red bandit]

Just a thought. Are you sure they are xs1100 carbs? And what size are your air inlet jets?

[Bonz]

Was the bike running previously with that same set up in the carburetors? If you were not the original owner and it was running, someone could've potentially drilled out jets.

[motoman]

deanstrictland.....110main jets across all four carbs.

[Bonz]

deanstrickland, how did the bike run on your ride? With pods and the exhaust system your signature describes, you would want slightly larger mains to account for those modifications. Motoman is correct, just like you shared on the specs, that 110's are the correct size.

Are you the original owner or did you pick this bike up used? I go back to the fact with that exhaust and pods, a previous owner could easily have had some Mikuni jets he could sacrifice and drilled them out to the hopefully correct diameter on the mains and the pilot.

[deanstrickland]

I tried running the bike with 42.5 pilots and size 110 mains. It ran so rich that my eyes were burning. I tried to screw all fuel adjustment (forgot the term) screws down. Plugs fouled, I think I got a whole ton of carbon build up on the valves and now I cant get it to turn over even with ether.

[bikerphil]

If you have a 1980, that is the transition year for the new type of carbs, the early ones still had the crossover passage in the pilot jet tunnel. You would need to install the rubber plug caps over the pilot jet tunnel. Without them, you would have a very rich condition as you describe.

[cajun31]

Dean... do your carbs look like either one of these? Notice the hole from the main cavity to the pilot jet cavity. If you have this then like Phil said you need the plugs to block off the pilot from the float bowl. They should only be fed from the main jet tunnel. Might well be why you are running so rich.