rejetted carbs now REALLY bad mpg

[xs1100rider]

this weekend i replaced my new jets on my 1980 xs1100 standard full dress bagger,120s on1/4 and 125 on 2/3,with the original 110.trying to get more mpg before i installed the other 120/125 in january i would get 50 mpg and that was with the pilot jets plugged.cleaned carbs and rejetted beginning of jan when i rebuilt the carbs with kits from georgefix off ebay.had issue with all the jets in the kit so i called him up and he sent me an extra set of 45 pilot jets.so i installed the 120/125 mains and 45 pilots with my drilled out(entire dimple removed) stock airbox with k&N filter,4 into 2 exhaust and it ran Great,but bad mpg(30-35?) and fouled plugs.so thinking the jets were too big went back to original 110 but kept pilot at 45 i went through half a tank of gas today in about 20 miles.i also left the airbox off of it when i reinstalled the carbs trying to save some work if i had to pull the carbs again,would the airbox make that big a deal.i checked the oil-no fuel,no fuel leaks either. thanks to all

[bikerphil]

You didn't mention what height the floats are set at. They should be at 23mm, carbs upside down, with float bowl gasket removed. Every time I rebuild the carbs with the mismatched main jets, I run all the same, all the way across (example, 120's).

[xs1100rider]

float height

never touched the floats,dont remmeber what i set them at. was told to run the 120 on outer and 125 on inner for the "cooloing effect" got poor mpg(but ran like a bat out of hell) and fouled plugs so i changed back to the 110 straight across now it gets even worse mpg and runs so so

[Ken Talbot]

Whip the carbs off, remove the float bowls and see where the floats are. Move them all 2mm leaner that where they are now i.e. "up" when he bank is upside-down. Don't get hung up about whether they're 23 or 25 or whatever right now, just move them 2mm, and make sure they're all the same. Then check your plugs and see what mileage you're getting.

[petejw]

another thing you could check is your oil level,
fuel may have leaked into the engine. This will also make the bike run like crap.
How did your bike run thru the rev range when u rode it?

[boyat68]

xs1100rider:

I suspect that you may have leaking carbs where the fuel flow does not turn off when the bowls are full. I suspect that the leak is not enough to allow fuel to collect in the air box (you took yours off), but enough to go through the carburetors and foul your plugs and get lousy mileage. This will happen if you have the vacuum cutoff petcocks as they cut the fuel off when the bike is parked. I suspect that if you turn the petcocks to prime while parked you may see that the carbs are leaking.

[81xsproject]

120/125 is too large. I run pods and 4-1 exhaust at sea level with 45 pilots and 117 mains. Forget about the mixed jets sizes, also. If you have K&N and 4-2, I would recommend going back to the 42.5 pilot and 115 mains.

[xs1100rider]

No leaks

I did check the oil -no fuel,after i installed the carbs on the bike i turned it to prime and walked away for a few minutes and no fuel leaked out so i know that they are not leaking out. I believe its just the jets giving me the problem.the bike bogged down on initial take off but over 3k ran ok. Thanks ken i will try your suggestion. And will also go back to the 42.5 pilot jet and try it after the snow clears,cause here in colorado we got a nice spring blizzard goin.

[CatatonicBug]

cause here in colorado we got a nice spring blizzard goin.

Funny you mention that - our Denver (Aurora) office is closing early due to "a light dusting of 12-24 inches of snow before 5pm" today.

[GaryF]

Please keep the snow there!
We are just about cleared out here in the north east
my heart goes out to you with 12-24 forcasted

[Ivan]

I'd be happy as all get out with 35 mpg.

50 is pretty rare to hear of on these bikes, or at least I haven't heard anyone say they get 50. Well, except for the guy that sold me my bike, but he also said it had a good engine.

Most of the time you hear 30-35 MPG. I have a sprung right wrist, so it won't stay out of the throttle, and I get bad mileage. there is nothing I can do about it.

Man, 50 mpg on a special, you could get over 200 miles on a tank!

[tarzan]

I'd like to get 50 mpg too.I get 38-39 pretty regularly.Less if I run it hard.
I run 110's in all four and 42.5 pilot jets.Stock exhaust and stock airbox with a k&n filter.Its a little toward the lean side but It runs good.I plan on going to 115
once I install the Kerker I bought on ebay about a month or so ago.