More carb problems

I have had repeated trouble with the carbs on my '86 VFR750, including, intermittently, gas overflowing from the overflow tubes. This cannot be good for mileage, and dumping raw fuel on the hot engine while underway seems perhaps even worse. I have cleaned the carbs, and checked that the floats were not stuck. It still leaked. I have the carbs off again now, and have removed the seats for the float needles. They are clean, and the needles seem to seat nicely in them. They seem to seat fine, and seal well. Why would gas still be overflowing? I am at a loss. As a minor note, two of the tiny filters did not come out with the brass seats. Should I worry about that? I am not sure how to remove them, or make them attach again to the seat.

 

How many miles have you been able to put on this bike since the last carb removal?

 

Where exactly is the fuel coming from?

 

Several hundred miles. Then it also developed another problem, where, twice, at almost exactly the same point five miles into a trip, it died, suddenly and completely. The starter would spin the engine, but no hope of firing. When I went back both times in the evening to figure out the problem, it started perfect, and took me home. That seemed electrical to me, and I contact cleaned all the spots in wiring harness I could get at. That issue rather reduced my riding. I am pretty sure that the fuel is coming from where the fatter overflow tee goes into the carb.

 

Are you against driving it to Sacramento and leaving it with me for a couple of days?

 

It may be easier in the long run.

 

I would have to make a lot of stops to fill the tank, and extinguish the flames. Still, it is a nice ride up the coast.

 

Is there anything that could hang up the float needle that I would not be able to detect? The floats all pivot nicely, the needles go up and down freely, they seem to seal fine. And yet, sometimes, gas gushes.

 

could the fuel pump be not regulating the pressure properly?? to much pressure?

 

I would, if he moved close enough for me to push the bike to his house.

 

I appreciate the offer, but Sac is a long way from San Diego, especially as work and children limit my mobility. Not sure what my next step should be, with the extracted carbs.

 

Remove the bowls and inspect if there is any big chunks of crud or debris in the bowls. Then turn the carbs upside down on your bench. Attach a plastic hose to the fuel inlet tee and blow thru the hose with your mouth. If the inlet valves are sealing then no air should flow. If air is flowing then try to determine which carb is not sealing and inspect for debris.

Do you have any fuel filters on your fuel lines? if not add one or more--you may have some debris or crud in your tank that is getting into the carbs and blocking the inlet valve from closing.

Do you have the original fuel lines? May want to replace them with new rubber, the inside of old lines can shed debris into the carbs and block the inlet valve from closing.

 

I tried blowing, and the needles seal nicely. I even tested moving the floats, and each one let the air in, and then resealed perfectly. They carbs were all spotless, and there is a new filter. I reinstalled the carbs (getting pretty good at that now, and can do it without using any obscenities), and started the bike, with the required pause for the pump to refill the hoses and bowls. Then gas dripped out. But now I cannot tell where it is coming from, as it just drips off the bottoms of the two back carbs. It looked as if the bowl seals failed, though it was more gas than I would have thought could make it past even bad seals. Enough drips to be almost a steady stream. I am not sure how to figure out the source now. The match suggestion above gets more appealing.

 

Excellent advice on the o-rings and bench test. You should find the culprit soon.

Are the plastic fuel rail tubes/tees loose--can you easily rotate the tubes or are they tight? If they are tight then the o-rings may be okay.

Has the bike recently been dropped, fallen over or wrecked? Maybe a cracked or dislodged fuel rail tube--inspect them with a magnifying glass if necessary. Also check the rubber fuel line and any plastic tees or fittings for splits especially if old.

 

Never happens, Gregg.


I think we all we all suspect the carbs were separated from the plenum at some recent time and that the fuel tube O-rings were disturbed or the tubes have a crack.

 

The fuel tees seem tight. The bike has not been dropped. I guess I need to pull the carbs again and see if I can find the course. Is there an easy way of pressurizing the fuel to the right level with the carbs away from the bike?