It doesn’t happen often, but when it does, it’s an easy fix. You know the drill…you open your fuel petcock on a carbureted bike, and a few seconds later you smell gasoline. And then a few seconds after that you see fuel on the ground, dripping from your bike. Most of the time, the culprit is a stuck fuel float valve in the carb’s float bowl.
In the old days, before there where vacuum lines and multiple cylinders and all kinds of complications, getting to the offending valve was a relatively easy fix. There would typically be three Phillips-head screws holding the float bowl to the carb, they came out, you gently pulled the pin holding the float to the carb, and the valve mechanism dropped out into your hand. You might see a bit of debris that held the valve open, or you might not.
Weirdly, in our world of fuel injected, multi-cylindered motorcycles, this happened to me twice in just the last few weeks. Once was at the very beginning of a Baja trip, and the other was just a day or two ago on my TT250. The fix was easy both times, except for access. Even on our simple single cylinder carbureted machines, the manufacturers have made getting to the float valve challenging. On my TT250, I had to loosen the clamp securing the rubber passageway from the carb to the airbox, pull that passageway away, and then remove the two nuts securing the intake manifold to the cylinder head. All this was just to get the carburetor away from the engine a bit so I could turn it enough to get access to those three little Phillips head screws on the float bowl. After I did that and I pulled the float (which works exactly like the one in your toilet bowl, which works exactly like the one in a wing-mounted F-16 drop tank, but that’s a story for another blog), the float valve dropped out. Sure enough, there was a bit of rubber debris (or was it detritus?) on the valve. I flicked it away, reassembled the thing, and oila, no more fuel leak.
The trick for me on a go-forward basis is to find a very tiny, very short Phillips head screwdriver that will allow me to get the thing under the float bowl with the carb still on the bike. That will turn a 20-minute job into a 20-second job the next time this happens. It’s off to Harbor Freight for me. I’ll keep you posted.