I'm restoring a 1948 M33 (M20 frame with B33 engine), which originally came with a 289 carb. It's in very poor condition and bordering on being scrapped. I see from 1955 the B33/M33 changed to the 376 carb. Is the 376 a better (i.e. more advanced) carb or would I be better in sticking with the 289 and getting a new/refurbished unit?
Thanks
My 1949 M33 runs a 376 monobloc. I have had no problems. The older carbs do tend to leak a bit. It all depends how much of a rivet counter you are.
I swopped worn 289 on a Matchless and a 276 on an M21 for monoblocs...They work very well, and have less potential for leaks!
And they are cheaper than new pre monoblocs.
I have a 47 B33, although the frame is much later. It seemed fine when I bought it except for an intermittent tick over. It also popped on the over run. I wasn't too bothered about the popping but the tick over did cause concern, mainly because I dreaded the engine stopping when at lights etc and being unable to re start. (Dodgy cartilage in right knee) Eventually I purchased a 376 from Surrey Cycles (extremely helpful Amal experts) which came jetted correctly for my engine, and when fitted the bike was transformed... real steady tick over and no over run popping in the exhaust. If I want to really impress myself I can progressively retard the engine and the tick over gets slower and slower until it resembles an old lorry engine with a massive flywheel.Essence!
Thanks for all the feedback guys, much appreciated.
they seem to be pretty tolerant on carb size. My 53 B33, I stuck a 1 5/32" 689 on it and that's all I've ever ridden it with. Seems fine and I've never thought about experimenting with other sizes.
I have run with a 389 monobloc on my 55 B33 for years with out a problem.