Re: 1944 BSA WDM20 boat anchor and other gearbox hell
I read these last posts with interest because I'm currently running in a new piston & bore in my WM20 taken out to 600cc. About 100 miles so far.
Speed is kept to about 40MPH, allowed to 45 on downgrades & not lugged. The plug colour is a nice mid brown.
The carby is a 1" 276 as my correct 1 1/16" has issues. Main jet's a 170 & the needle's in #2 groove. Would it be a good idea to richen the mixture, & would I raise the needle, use a bigger main jet or both?
Re: 1944 BSA WDM20 boat anchor and other gearbox hell
Bob I presume you have fitted an M21 crank? The Amal book quotes a 160 main jet and needle position 2, but in a 1 1/16" carb. I'm not sure how it calculates with the smaller carb. Maybe raise the needle a notch for running in and see how the plug looks from then. Ron
Re: 1944 BSA WDM20 boat anchor and other gearbox hell
Hi Ron, thanks for the reply. Yes, there's an M21 crank in the engine so for practical purposes the engine's a standard M21.
I'm glad you pointed out the 160 main jet, I'd thought it was a 170. So while the carb settings are a bit mixed up for an M21, it's not too lean. I'll raise the needle a notch for the running in.
