Screws in idle jet passages on center carbs

[greengoon3]

When disassembling my recent acqusition of a rack of carbs I noted the 2 center sets had a screw in the pilot jet accesses. Any idea about this ?
Do I just remove them and install the pilot jets like the other 2 carbs?

Thanks
George

[TopCatGr58]

Hey there George,

Did the outer 2 carbs NOT have a screw sealing the pilot jet tower?? IF it's an earlier series of carbs, ALL 4 pilot jet towers are to be capped, the pilot jet gets it's supply thru the little tunnel between it and the MAIN JET Tower, and that's why the MAIN jets are so much larger than the later model carbs. You do not want the carbs/pilots feeding directly from the float bowl!!
T.C.

[bikerphil]

Yes, the pilot jets are under those screws. There should also be screws on the other two. If they are missing, it won't run right. Sounds like you have the early type carbs w/brass floats.

[tarzan]

Sounds strange to me.I have an SG also and it has pilot jets in all four.Not sure why someone would block two off.I have seen people talk about plugs on some models because some were drilled so the idle circuit feeds off the main circuit(IIRC). However I have not seen that myself.But I would suspect that it would be an all plugs or all jets situation.However someone else will be able to clarify I'm sure.
All the XS carbs I've been through have been off SG's and none had plugs in place of pilot jets.I have only rebuilt three sets,so I am no expert on XS at this point.But they all ran good.
And by the way welcome to xs11.
Rick

[TopCatGr58]

Hey Tarzan,

Just for your information, these older carbs STILL have pilot jets, it's just that the pilot jet tower is capped off so that it will direct it's fuel draw thru that tunnel to the main jet tower. The later carbs that you're familiar with have smaller main jets, 110-120 and NO sharing tunnel, and so the pilot jet towers are NOT capped, so that they can feed directly from the float bowl fuel supply.

Not sure if someone might have mixed and matched Georges bank of carbs, putting newer styled on the outer pair, and the older on the inner pair. The upper vent ports to the outside of the carb body is still there on the newer carbs, it's just sealed, and so the inner carbs would still be able to vent thru the connecting "T" fitting. The outer carbs would have their bowl vents going thru the inlet bell..that extra 4th hole in it, vs. the earlier carbs that only have 3 ports on the inlet bell.
T.C.

[tarzan]

Thanks for the heads up TC.
Now he has a later model bike right?
Do we know for sure he has the early carbs?
Will those plugs fit in the late carbs ,yet impede flow?
Could a PO have got hold of the plugs in a kit and tried to use them?

[DGXSER]

Can you also distinguish if it is the earlier or later carb by the mixture screw??

I think the earlier carbs that hve the covered pilot jets had the exposed mixture screws and the later carbs with the uncovered pilot jets had the mixture screw down in the tunnel.

[Ken Talbot]

The mixture screws on the early model carbs are very sharp and pointy. The screws on later carbs are quite blunt. Broken-off early screws look blunt, but not the same as later screws.

Broken-off early screw on left, blunt later screw on right:





.