Gasoline Contaminated Clutches | Tech Tip

Cursed Clutches

In the December 2010 issue, Pat Duff wrote in requesting some info on his 1986 Triumph Thunderbird. Specifically, he was having trouble disengaging the clutch and wanted to know how much travel the release mechanism needed to separate the plates. I couldn't provide the answer; it simply wasn't listed. But another reader and a friend of mine, a fellow named Jim Hamlin, who does some first-class wrenching down at the local Triumph dealership, mentioned to me that he'd had a T-Bird show up with exactly the same problem.

Everything looked fine, but Jim noticed that there was a strong smell of gasoline coming from the crankcase. When he measured the fiber plates and found they were slightly thicker than they were supposed to be, he rightly surmised that a leaking petcock and sticky carburetor float had created a perfect storm and allowed fuel to enter the crankcase. The fuel had swollen the fiber clutch plates, and prevented them from fully disengaging. Replacing the clutch plates cured the dragging clutch, and installing a new petcock and cleaning the carburetors took care of the rest of the problem.

In any event, although both T-Birds had clutch trouble, I have no way of knowing what caused Mr. Duff's problem: He didn't mention any odor of gasoline, and there are certainly a variety of other issues that might have caused his problem. Since I haven't heard of any other T-Birds with gasoline contaminated clutches, I'm going to assume the one my buddy ran into was an isolated incident.

That being said, this is the type of problem that could affect any bike where the engine and clutch share a common oil supply, so it's something to consider should you suddenly find yourself with a sticky clutch and poor fuel economy.