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Tech Corner

Technical Q and A for classic motorcycle maintenance and repair.

Triumph Bonneville Carburetors

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.

Bonneville carburetors

Q: Can you give me any advice on carburetors for my 1970 Triumph Bonneville? Right now the bike is using Amal 930/43-930/44 carbs, which I believe are worn out. Do you know which new ones will fit the bike? Would it be the 930/9 or will the 930/300-930/301 premium be better? — Graham Rashleigh, U.K./via email

A: I’m a big fan of using original carbs on these bikes. That way someone else has taken the time to figure out the jetting and slide cutaway. With that in mind, the Amal carb website shows either the 930/43-44 standard carbs or the 930/43-44 premium carbs for your model Bonnie. ACK145 is the carb set for the standard and PACK145 is the premium set. I like the features of the premium carbs — improved metallurgy, improved idle circuit and stay-up floats — but you do have to consider the extra cost. A less expensive option I’ve used here in the U.S. is having the carbs sleeved. I don’t know of any firms offering that in the U.K., however. Here it costs about $100 per carb to have the bodies bored out and the slides turned down and sleeved with stainless steel. That brings them back to original tolerances and removes the sloppy fit of slide to body. Having dissimilar metals in the body and slide then reduces the rapid wear you get from the original setup. MC