Motorcycle Classics Blogs > Tech Corner

Tech Corner

Technical Q and A for classic motorcycle maintenance and repair.

Gas Tank: Triumph Bonneville Special T140D

Motorcycle Classics tech expert Keith Fellenstein

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.

A bigger tank

Q: I have a 1979 Triumph Bonneville Special T140D. I am interested in using it for touring and am pondering an upgrade to the U.K.-spec gas tank, which has about twice the fuel capacity of my stock U.S.-spec tank. Would I have to modify my seat or anything else? Also, do you have any suggestions on locating a U.K. tank or a well-made reproduction? — Boyd Smith/via email

A: The parts book for the 1979 T140D model shows two different gas tanks, the 3.6-gallon U.S. version and the 4.8-gallon (4-gallon Imperial) British version. And yes, you will have to change out your seat assembly to accommodate the larger tank. The tank badges are different for the different tanks, too, so either get a complete tank with badges or make sure you can get badges for the larger tank. I wasn’t able to find a U.K.-spec tank in my searches, but you might email Burton Bike Bits and see if they can offer any guidance. MC