Xj700 - Fuel Leaking out Overflow

Hey all, hoping someone can give me some pointers here. I have recently dismantled, cleaned (carefully) and fixed up my carbs on my 85 XJ700.

When I did this I used a float bowl replacement kit, and thought I had done it correctly.

Good news is the bike started like a champ immediately, no hesitation, no roughness. Bad news though...

Fuel is still leaking out the overflow. I did note that the tabs that go into the needle valves are a little tired looking, so I am not sure where they should be set. Can anyone give me some pointers on setting these properly as well as anything else to look for?

Thanks for the help.

-Jason

 

Welcome to the site yesterdayze.

The tang on the float assembly is used to adjust the fuel level in the carb. Either the float level is set too high or the float valve is stuck and you’ve got too much fuel and it’s running out of your overflows. You can try tapping on the carb float bowl and see if the fuel stops, this will rattle the float valve and allow it to shut off the flow. If this doesn’t help then you should check the float levels, which should have been done when you had the carbs off.

Here’s one link with some pictures of setting the float level on the bench.
http://www.xjbikes.com/Forums/viewtopic ... level.html

From the XJCD, the fuel level on an XJ700 should be 1.0 +/- 1.0 mm below the carb body of a vertically positioned carb.

Hope this helps.

 

Nick - Thanks for the welcome and feedback, I'll give that shot tomorrow and see how it goes. When I put these back together I had set it so that when the float was parrallel with the casing it made it so that I could no longer blow air through (used a hose and my mouth). So most likely I have it set to high.

Someone also mentioned that it is possible that the floats no longer float. Ever heard of that happening? (So much fun to get those carbs on and off....lol...) Thanks again for the help, I'll let you know what happens after Saturdays test.

 

An easy way to check your float level while they are still on the bike is to get some clear aquarium air hose and fit it in the carb bowl drains. Hold the tube above the carb and see where the fuel stops in the prime position without the engine runing.

 

"Floats No Longer Floating" = holes in the float

But I agree, probably set to high or stuck float. The float sticks occasionally in my Honda. To test and see if its that, just take a long screwdriver, put the head on the bowl and tap the handle with a hammer (lightly, you are just trying to free up the float). If the fuel stops pouring out, that's your problem.

Hope that helps.

 

Alright, did some more tests on it this weekend, I am definitely going to have to adjust the carbs (which I knew, just didn't know how far off they would be, ...ouch...). I have seen numerous threads on that, so I will check those out.

I think it may have been sticking floats, after running it a bit and giving it a few taps, it stopped overflowing quit so much, still some, but only at times. I will pull the carbs back off and see what I can do. I know that the pins holding the floats were a little nasty, maybe it is time I try to find something to replace the pins with.

Thanks guys. I'll post again when I get a chance to pull the carbs and set them.

 

Okay, I pulled the carbs, set the float levels using clear tubing, not 100% certain I have them right, but I set them to the same level I saw listed as 'purrfect' in one of the linked posts above. Made sure nothing was sticking and put the carbs back on. Jets, slides etc are crystal clean. Turned over bike, it didn't want to at first, finally got it to go but it appear that only the 2 and 3rd chambers are firing when under 2500rpm. If I give it any gas it dies, unless I start it holding the gas 1/4 open, then I can safely rev it after. I fiddled with the pilot screws on top, not sure if I am missing something there, but they appeared to not have much, if any affect on anything.

Over 2500 rpm they will all fire with the third becoming intermittent. Compression is good on all of the pistons except the first which is a little lower then specs but still there. Checked alternator, that is good, checked wires, those are good, all plugs are new and sparking. Swapped around the plugs to no avail. I am stumped.

At this point, any help would be great. Thanks guys.

 

Pilot Screw's set at 2.75 turns out.
Floats set so level is 2 mm below bowl rim.
Compression in 1 = 85psi, 2 = 135psi, 3 = 145psi,4=135psi - Yeah I know 1 needs to be addressed, working on it, probably a sticky valve, checked the rings and they seem fine. (Oil check)
Alternator/Generator - Good brushes, clean and running well.
Wiring harness - Cleaned and checked all contacts, swapped out TCI with spare, no diference.
Plugs - New, Gapped properly. All have been checked for spark so coils and plugs are good.
Boots, solid and flexible. No cracks.
Slides drop beautifully, no hesitation, no staggering. No tears, springs are great.

So it looks like I am running too rich (which would explain why any gas added by throttling it will cause it to die....flooding...)

It is sucking gas down like there is no tomorrow, but ONLY when it is running, so don't think it is floats as I can (and tested this) hook a can of gas to the carbs via a hose and leave it over night without it flooding or loosing any level in the can. Turn it over and once it begins to run it will down 16 ounces of gas in less then 2 minutes....that isn't right.... That would be 1 gallon every 16 minutes or so, or roughly 4 gallons an hour....a staggering 15 mpg at 60 mph give or take.

I CANNOT start it with the choke in, have to open the choke up to start, so pilots are not too rich.

Hope this info is useful.

 

Okay, so I finally got a copy of the manufactures service manual. They list my exact problem as being due to the compression being more then 14lbs difference between the cylinders. Didn't know they were that finicky. So I did the only sensible thing and pulled the motor, tore the head off. Checked the pistons and rings, seemed okay. Valves looked kinda rough though so I cleaned them up the best I could. Had everything all but sparkling when I was done. Put it all back together, it's now down about 30 psi on each chamber give or take. So that was not so good, some of the sludge was probably helping the seals.

I guess now it is off to go find a machine shop to redo the valves and while I am at it I will have them re-hone the piston walls and re-ring the pistons.

Anyone know where I can get new valves, valve guides and piston rings for an xj700?

Thanks.