My 1988 CBR 600f pours gas out of the intake to the engine from the fuel pump line.

I have cleaned the carb jets, changed the relay, and tried a different fuel pump. All made no difference. The fuel pump pumps too much, but I think that is a result of the lack of pressure once the fuel starts overflowing out of where the fuel line out of the pump meets the engine intake.

Any suggestions what else would cause this problem and what I can try to fix it?

 

Its a little unclear what your saying. Is the gas coming out of the carb vent lines? Or just pouring out from the line itself that leads to the carbs? Is it pouring down the carb into the engine?

If its out of the vent lines, the floats are probably not adjusted correctly in the carbs. if you cleaned them. Did you remove the needle from the floats? if so, is it possible the needle was put back on incorrectly? Is it possible the tabs were bent on the floats?

If the gas is coming from the inlet line. Its possible the o-rings are bad, or there are cracks somewhere.

If you can post back with a little better description of exactly where the gas is coming from, someone here will be able to help.

 

Also, make sure you blow each passage, both pilot and main, out with carb cleaner and compressed air. Continue to blow out all the other passages in the carb (fuel in and the in between lines).

You wouldn't believe how easy it is for a little bit of gunk to get on the end of that rubber part of the float needle and ruin your day.

 

The gas is pouring out of where the inlet line meets the engine. It is not leaking out of the line itself, but the pump is over pumping, which causes too much fuel in the line for the engine to handle and the fuel pours out from where the inlet line clamps onto the carb inlet.

I have heard and seen that the floats might be the problem. I did check them and measure the distance of the tabs when I cleaned the carb jets, but I'm going to check them again tomorrow.

 

I would check the fitting where it attaches. Those pumps are really low pressure. They are only around 1-2 psi, and very unlikely the fuel pump is over pressurizing the system. If the floats are stuck open, then its possible the carbs are overfilling. But it would be coming out of the carb vents, not the inlet line. Since its the inlet line, I would inspect the fitting. Then also inspect the clamp to make sure its tight. Also, make sure the clamp is not on the end of the fitting, it needs to be seated on the tube itself. If its clamped on the fittings end, it won't seal right. Also, if your using a spring tension clamp, ditch it and get a screw type that you can tighten up. A lot of times, those hoses shrink and the tension type clamp no longer puts enough pressure on the hose to seal it.

I would at least check those things before tearing into the carbs again.

 

I'll second Squibs comments.
Get a jubilee clip for the fuel pipe and ditch the spring clamp. If you don't have a clamp at all and are just relying on the rubber tube its self to fit over the inlet nipple on the carbs it's perhaps a sign that your hose needs replacing. None of this should cost you more that a couple of bucks so go the easy route before tearing the carbs apart again. Sounds like you've already doe a decent job in there.
Good luck.

 

one other thing you might wanna try is to go on the right side of the bike near the cdi box and there is a 3 pin relay there. unplug and your problem should go away. from there you are going to have to figure out if the relay is sticking causing the pump to stay running or if there is something else going on. The test for the fuel pump is to unplug that relay and jump that connector and the pump will continiously run and obviously if it runs long enough it will pour right out of the front of the bike.(happened to me last summer when I was testing)

 

The fuel lines don't actually meet the engine. The fuel lines attach to a "T" fitting that is inbetween the carburetors. Can you provide a better description of where the fuel is leaking from ? A 1988 motorcycle is really old. The "O" rings are going to be really hard and brittle. They're really prone to leaking.

This is not from a 600F, but you get the idea.


After cleaning up the white crust off the "O" rings, you can see the pitts in the rubber. They're also really hard. This is off a 1998, which is 10 years newer.

 

Thanks for all of the help, everyone. I'll definitely replace the squeeze clamp, and the o-rings where the inlet line clamps onto the t before I go back into the carbs.

 

Update:

Replacing the o-rings did the trick! No more gas everywhere. Thanks for all of the help!