David Rutherford´s BSA B50 Racer
Here are the details on the bike. The stock frame has had the back half of the oil tank tube removed and
two 1" diameter chrome moly tubes extend from the top of the shock mounts to the back bone tube at the rear
of the gas tank. The downttubes are modified accordingly to make room for a 40 mm Mk II Amal carb.
This particular set up uses a crank mounted PVL ignition, although a Boyer with Accel coil fired by either a
stock stator and rotor or a total loss battery system are also used. The head is twin plugged and ported by Ted
Hubbard with a 1-7/8" exhaust.
I try to run approximately 28 degrees advance. Plugs are Champion C57R.
Titanium valves by Ted Hubbard with R&D springs. The piston is J&E sourced through E&V Engineering, atop a 6-1/2"
titanium rod from Dickerson Machine. The crank is assembled and balanced by E&V Engineering. Compression is about
10.8 - 11.0:1. The stock clutch assembly is used with a lightened chain wheel, an alloy pressure plate and Barnett plates.
A 19 tooth countershaft sprocket is used with a Renold 520 chain. Front and rear hubs are stock but lightened.
Rear sprocket for long tracks (Daytona, Road Atlanta, Savannah) is 46 tooth, ranging up to 54 tooth for short circuits like Talladega.
Exhaust is a personal design with no internal baffles; the reverse cone is sufficient to pass WERA Vintage and AHRMA noise levels.
The belly pan (required by WERA Vintage and next year by AHRMA) is simply a fiberglass cast based upon B50MX bash plate.
Front rim is a WM2 flanged Akront with a 110/80-18 Avon. Rear is WM3 flanged Akront with a 110/80-18 Avon; sometimes I run a 130/80-18 rear.
If so, the left side of the tire needs to be shaved a bit to clear the chain. A Kawasaki style steering damper is affixed to
the tubes by a 35mm clamp and the frame via a 38mm clamp. Throttle is an Amal aluminum body ¼ turn. Levers are Magura,
and the tach is a Scitsu. Clip-ons are from Woodcraft. Vintage Brake linings are used in the front brake and stock linings are at the rear.
Seat is an AJS 7R. Gearbox is stock with the cam plate reversed for GP style shift pattern.
I think that about covers it. It's a pretty small B50 racing crowd here in the US, and we all know each other as well as what
works and does not work on each other's bikes.
Hence, there are not a lot of secrets.
Atlanta Georgia. USA
Updated 11:39 2003-11-25
© Rickard Nebrér