[mfhutchins]

i bought this bike and it ran like a champ until i took it to work one morning about 2 weeks ago...........on the highway. since then, 3 things have happened. the voltage meter that is built into the headlamp came off (small problem), the speedometer stopped working (slightly bigger problem), and there is a "puttering" coming out of the left muffler. single amal carb. no puttering when i accelerate, only when i am cruising at a constant speed. it is a fast puttering. i dismantled the speedo and found that the square metal tenon that is inserted into the back doesn't spin when i'm riding, which must mean the part that is attached to the rear wheel is broken. any suggestions anyone?

 

[kenessex]

I would suspect points or valves need adjustment. The hard run either wore the points rubbing block down so the gap closed up or either the valves seated in, the rocker is a little worn or you slightly bent a pushrod. So, pretend it needs a tune up and check the valves and points.
If thats not then you have to give me the BSA and I'll give you my Honda or Yamaha in trade.
Ken

AHRMA 412
Vintage racing - old guys on old bikes

 

[mikeo]

I would be suspicious of the carb for the puttering. Amal concentrics are not really very good carbs. If it original or been on the bike for few miles then I would look at the idle circuit and/or replacing it with a brand new one, or better yet a brand new equivalent size monoblock (which in my opinion)is a better carb.

As for the spedo its most likely the cable. The inner cable should pull out from the spedo end and have square "tenons", as you call them, at either end. My bet is its broken. If you get a new one get the whole thing (inner and outer). They're available any where that sells vintage british parts.

Mike O.