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 the subject.
Q: I have a 1984 Honda VF700F Interceptor, which I bought new. It ran flawlessly for 20 years until it started having trouble idling. I took the carburetors apart, cleaned everything up, put it back together and it ran like new for a few years until the idling problems started coming back. Last fall I brought it to a local shop, which rebuilt the carburetors, cleaned the tank and did a full service. Last week it started having trouble idling again. If memory serves me correctly, the pilot jets in this bike are very small, which leads me to believe that there is a compatibility problem between my bike and modern fuel. For 20 years this bike ran great on any fuel I put in it. Before the idling problems I would never shut the fuel off or run the bike in the winter. Now it has to be run every week or it will stop idling correctly. Do you know of a fuel that will stop this from happening? — Charlie Linley/Easton, Conn.
A: This is a problem for many of us, as we are running motorcycles on modern fuel mixtures different than what the motorcycles were tuned for. The component that gets most of the blame is ethanol. It would be worth your while to find a local station that promotes its fuel as ethanol-free. Run two or three tanks of ethanol-free fuel through it and see if that cures the problem. In my locality, Phillips 66 advertises ethanol-free gas. Your area may have a different vendor offering the same fuel. One way to find pure gas is to check pure-gas.org for your location. If the fuel change doesn’t help, you’ll have to investigate richening the idle jets. MC