Fuel level issue with one carb

Howdy-

I have been away from this forum for a very long time. We moved to a new city in 2013 and I started a different job. I have had no time for cycles or wrenching in general since then, but am FINALLY working on my '81 650 again. When I stored it, I had a fuel level issue that had stumped me, so I dug into that again recently.

I've rebuilt quite a few racks of XJ carbs over the years and have always dreaded setting fuel levels. Occasionally I've spent more than one full day on a rack before I finally had it right. I've never had as much trouble, though, as I'm having with the #2 carb on this bike. I'm completely stymied. The several times that I've thought I had it, I put 'em back on the bike and it overflows. Back it off by a whisker, then it's way low.

I always secure the rack in a clamp and level it carefully when I test. Kind of at my wits end.

Thanks - JAY

 

could be your needle valve is binding or your float is binding.
make sure the seat of the needle valve body is clean
in the xj4ever catalog they sell washer shims that go on the float pin to keep it from binding

 

When I do mine I leave them on the level bracket for at least an hour, during which time I purposely bump and move them just to be sure they don't overflow. Learned that the hard way. Also, if you have the rubber tipped needles I would replace them in case they are hardened or misformed. I got the solid brass needles and seats from Chacal and have had no problems.

 

This is possible, I suppose, although I've polished that float pin and the bores on the float that receive it. I've also tried a different float just in case there was some abrasion that might be causing it not to move freely.

Not familiar with the shims you've described. Can't quite picture how a washer would accomplish this.

 

I'll have to take a look at the needle tips. I've never had trouble with rubber-tipped needles, but who knows...?

 

washer goes on float pin to reduce sideways movement the whole float pin slop.
from xj4ever catalog fuel system listed with floats
kl7) Aftermarket Hitachi FLOATS, FLOAT PINS, AND SHIMS:

Unlike the Mikuni carbs, Hitachi carb FLOATS used a loose-fitting hinge PIN to secure the float to the cast float posts in the bottom of the carb body. Additionally, the formed "tube" that the float pin slides thru on the float bracket arm is somewhat "short" in overall length compared to the distance between the float posts, resulting in a float that typically has quite a bit of side-to-side "slop" in its motion and movement. This slop can allow quite a bit of erratic movement in the float on the pin, and can contribute to difficulties with getting the fuel level set properly and consistently on these carbs.

 

Interesting, thanks.

 

unless your needles are old and hard it should be no problem the "rubber"tip.

 

look at the tang on the float, if it has any scratches on it the pin on the needle might be hanging up on it. smooth it out with 1000 grit.
if all else fails, swap some parts from one of the other carbs. maybe those parts just don't get along in that body
or
3 out of 4 aint bad