1981 XJ650LH Fuel Leak

Hello, I'm working on my neighbor's 1981 XJ650LH Maxim. When he brought it to me, the sump was full of gasoline, and the air cleaner soaked with gasoline and oil. Having been doing this for over 30 years, I replaced the needles, seats and screens with parts purchased from XJ4ever. Upon doing so, I also set the fuel levels.

The bike still leaks fuel but not so obviously.

It appears as though fuel is creeping up along the main jet nozzles. The area around the needles on all four carburetors gets slightly wet with fuel. If left to sit overnight with my auxiliary fuel supply connected and the petcock shut-off, very tiny puddles forms around two of the throttle butterflies . I checked the copper washers under the main jets for flatness, and even applied a bit of Hylomar to the washers to ensure they're sealing. Obviously, something isn't sealing. I was wondering if anone else has encountered this problem and what measures, if any, were taken to remedy it. This bike has me defeated and demoralized.

 

That is really odd. Did you wet-set the fuel levels to be sure that the float needles are getting fully shut?

 

use a clear tube to check the fuel level. Hylomar is good stuff but the main jet has a hole in it.
if the fuel line was empty, the needle valves are leaking. if the line was full, the petcock is leaking

 

It's also worth noting that there is at least one brand of rebuild kit that contains float needles that don't quite sit right in the seat bores. They can get a bit cockeyed and stick.

 

Thank you for the replies. Yes, I "wet" set the floats. I even lowered the fuel levels, and still the problem persists. The bike had new needles and seats when I received it. After multiple attempts to get things to seal, I came to this site and was directed to XJ4ever and purchased recommended needles and seats. The new needles and seats stopped the excessive leakage immediately, but still have the fuel creeping problem. I did notice that the main jet nozzles don't fit snugly in their bores. I'm wondering if the slight play is allowing fuel to creep up. If that's a tolerance fit, then I'm ready to condemn the carburetors. The bike had been sitting for 25 years and the aluminum inside the carburetor bodies is a bit corroded. Buying a used set , especially from a bike that hasn't been in service for years concerns me; I don't want the same problem.

 

The problem can't be with the fit of the needle jets. The fuel level won't go any higher than the floats and float needles allow, and gasoline does not creep up through capillary action anywhere near as easily as water does.

Was the petcock rebuilt?
It is possible for a constantly leaking petcock to force gasoline past the float needes as the bike sits.

 

to save old ones i burnish the seat with 0000 steel wool on a Q-tip then a few spins on the needle, you could try that.
did you start the bike, sometimes the vibration lets the needle find the seat better

 

I believe the problem was, in fact, with the fuel levels. While I did "wet set" the floats, I made the novice mistake of setting the float heights and 17.5 mm and calling it "good enough" (it is for most Hondas). Wrong! After several painstaking hours of adjusting the actual fuel levels to get them in the specified 2-4mm range there appears to be no leakage. I'm going to leave the carbs set in the bike overnight and see if gasoline gets into the sump and/or airbox. If not, I think the problem is solved. I'm cautiously optimistic. I did notice that the motorcycle petcock drips occasionally...I don't know if that's going to be an issue.

 

A small drip from the petcock won't be a problem as long as the float needles are sealing.

 

The 17.5 initial dry float setting is for quite a few of the hitachi carbs, but for the 650turbo, you should have Mikuni BS30 carbs. The wet levels are specified in the Information Overload