Forum bmwbike.com

Does any one have experience with non original carburatores? The original Fischer-
Amal are difficult to find. What kind of carburatore will fit in the R51? Maybe a bigger
bore? Thanks for your answer.

regards,
Ueli Schmid

Hello...you can use a 1/22/39-40 from an R51/2, or a 1/22/61-62 from a early R51/3...you could get away with a 1/24/...from a later R51/3. The problem really relates to getting the air intake tubes to fit properly, but almost any plunger or swingarm twin Bing carb will bolt onto the head . If you have any part of the Amal Fischers left, some British Amal parts will retrofit. Good luck

Ulrich, Before considering fixing carburettors from "later" model BMWs to your pre-war R 51, have a careful look at the angle of the float bowls in relation to the body of the carb. "Later" models featured a downdraft style body with the bowl cast so that the float is level. Fitting a downdraft style carb. to a head with a vertical mounting may result in a float that is not "level".

Good luck.

PeeVee

By the way, I'm told that it's easy to grind the words "Mikuni" off a 22mm carb!!

My R6 came with Bing carbs from an R50. The floats are slightly inclined, but these carbs work better than the correct Fisher Amal carbs that I purchased later.

I have not noticed any problems caused by the inclined floats.

Best regards,

Bruce