Technical Q and A for classic motorcycle maintenance and repair.
Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as your subject.
1970 BSA Victor Special Leaking Fuel
Q: I have a 1970 BSA Victor Special and have a question about a leaking carburetor. Other than the fact that the petcock leaks fuel into the carb, why does the carb leak fuel into the air cleaner? I have owned the bike from brand new and only have just turned 2,500 miles. I have kept this bike pristine and use it only occasionally in the summer. As you know, they can be difficult to start, and I have a bad kicker leg. Over the last two years I have been touching it up a little, polishing bolts, repainting the frame, etc. I took the carb off and cleaned the surface, and took it apart and cleaned up the inside float bowl. I took apart what came apart easily and cleaned the fuel strainer and so forth. I know it is back together correctly, which is not difficult anyhow. I did have to make a new gasket, but cut it exactly like the original. The float and needle valve (plastic needle) all looked like new. My thought is that the float is not coming up far enough to push the needle valve tight or the needle is malformed, but again it was smooth and the carb did not leak before taking it apart. Any thoughts? — Larry Bush, via email
A: I’ve always liked Victors and I have worked on several. I still kick myself for passing on the opportunity to buy one years ago because I thought it was too costly. For the time being, I’ll have to settle for my Royal Enfield Bullet 500, a mild-mannered substitute for the high-spirited BSA. Regarding your problem, I suspect a couple of things. First, is the gasket you cut interfering with the hinge for the float? I often have to trim the pattern gaskets to keep them from bearing on the hinge and impeding the float. Second, it’s probably time to replace that plastic needle with a brass one with a Viton tip. I seem to recall concerns with the nylon needle not having enough mass to resist being pushed open by the pressure of the gas. That may be an old legend, but the Viton tip will seal better than the hard plastic. Just make sure they are the same length, otherwise you’ll have to go through the difficult task of setting the float level in an Amal Concentric. Also, on starting: if you have the energy transfer (ETC) ignition system it’s easier to sneak up on compression without fear of the bike kicking back. I rely on the compression release to get past TDC, and then give a firm stroke on the kicker, making sure to follow through to the end of the kicker travel. If you have a battery and points you follow the same procedure, but don’t turn the ignition on until you get past TDC. MC