XJ 1100 carb questions.

[foxjohnc]

I am fixing a set of XJ 1100 carbs for a friend and have some questions. First off, one of the carbs was destroyed by some idiot who was trying to clean them. They succeeded in cracking the body of the carburator on the top by the vacuum diaphragm. There is actually a 1/2 inch piece missing. I have a set of XS 650 34mm Mikunis that I am trying to use. I am planning on using all of the internals from the 1100 carb with the 650 body. The bodys are nearly identical except for a few things. The 1100 carbs have an adjustable jet on the top near the front of the carb while the 650 carb is non adjustable. Also the carb is #2 from the left and it has a fitting and a hose coming from it on the top near the front. I'm assuming this is for the petcock or for a vacuum advance. The 650 carb does not have this but the manifold from the 650 has the same kind of fitting so I am wondering if I can just hook the hose that normally hooks to the carb up to the manifold.

[sixtysix]

On the earlier models (XS's) the port in the #2 carb is for the vac advance, and id not the same as the manifold port. The XJ does not have a vacuume advance right? For any of the the carb specific stuff I would get hold of Rob Reil at www.motorcyclecarbs.com he knows these old carbs inside and out and can tell you exactly what the differences are.

[Mike Hart]

The XJ does have a vacuum advance, but it is different - the #2 carb vac port is connected via short hose to a vacuum sensor which provides a signal to the black box. The vac sensor is just above the carbs, under the tank.

[foxjohnc]

So if I change manifolds to the one with the hose fitting it should work? Will the fixed jet (idle jet?) On the top of the 650 carb cause me any grief?

[foxjohnc]

I have a set of carbs from an older xs 1100 that I am trying to get working on the bike. Can someone tell me what the differences between the two sets are? It looks like there are two fuel inputs on each 2 carbs. The fuel input looks almost identical to that on my xj carbs but there is another input above that one. Do I just run a T fitting from the octopus to the fuel intakes on each carb? The choke setup is different from the xj carbs but I will use the choke rod and hardware from the xj on the other carbs.

[TopCatGr58]

Hey there Fox,

The lower "T" fitting is the only fuel fittings, the one that is between each pair at bowl level! The other fittings are vent tubes, sounds like you have a set from a 78-79 since the 80-81's didn't have that extra vent tubing on top. I haven't actually worked with a set of those, and can't remember exactly, but I don't think you should cap them off otherwise the carbs can't vent properly, but I'm not sure how others recommended securing them and covering the ends, like with a fuel filter just to prevent dirt and stuff from getting down in there!?

HTH......T.C.

[Ken Talbot]

The upper "T"s, which vent the float bowl, are meant to be plumbed to two small nipples on the upper section of the airbox. If you have the stock, older model airbox, the nipples will be plugged and you'll have to drill them out to get the venting to work. You could also run them up under the tank and install a small crankcase vent type filter or fuel filter on each.