HOME and how to join Forum Open Area General Scott topics Mag for 1930 TT Rep Re: Re: Mag for 1930 TT Rep



I have sent photos of the BTH magneto to your e-mail address. As you will see, the type is KCV50 A1. Serial number is 1F 307922.
I am using a replica BTH electronic magneto on my Vincent Black Shadow, and I am very satisfied with it. I have two other BTH replica magnetos made for Scott. One of them is the new type where you can put the Lucas generator on top. It will then look a lot like the ordinary Lucas MagDyno. I have not used any of them yet, but will try the new type magneto on my 1936 Scott, which I use as a test bed. The 1936 Scott has a Roger Moss tuned engine with a tungsten-balanced crankshaft, hi-compression head and flow tuned transfer ports, Silk pistons with “windows” etc. It goes very well with the original (overhauled) MagDyno, but it is a fact that the magneto is one of two Achilles-heels on a Scott (the other is the clutch). The magneto runs at engine speed on a Scott and has a hard life. On an “ordinary” bike it would run at a half of engine speed.
With the original magneto, everything is well up to ca. 4000 rpm. Then the magneto starts giving erratic sparks, and the power drops. There will be violent vibrations in the engine until it gives up around 4.400 rpm. On a Moss-tuned engine the torque/power curve rises steeply from 3.500 to 4.000 rpm, and power would undoubtedly continue to rise if the magneto could cope with the engine speed. This is where the electronic BTH “magneto” allegedly is superior. It will function normally with much higher engine speeds than the Lucas magneto. In addition it will give a “fatter” spark at low revolutions, making starting easier.
My TT-rep 1930 is not Moss-tuned, but has been used for grass-track racing etc. in the 1930’s and functions very well with the original BTH magneto – at least well enough for my use. It seems to me that the BTH was a better magneto than the Lucas, but this is only based on subjective observation.

On my Henderson 1928 DeLuxe, there Is a BTH magneto, probably from a Tiger Moth or Gypsy Moth. A beautiful piece of work. I have just overhauled it, and I was impressed with the quality of both mechanical and electrical parts.



Kind regards,