I’ve been a bit detuned this year by health and other matters so I didn’t make it to the Stafford Show. As someone who is a bit of a sucker for electronic gismos on old bikes, I was very interested in Roger’s comments in the latest YOWL. However I do feel the need to correct an impression that he may have given about the BTH “magneto” – not often that you have to correct Roger!
Firsty, if anybody is interested in the new German magdyno replacement the website is : http://www.dynamo.mz-b.de I found it by chance when researching a replacement for the dire electrics on a 1950 s BMW.
Regarding the BTH magneto replacement: they DO make a version wiith auto advance and retard, I know because Tony Harris at BTH made me one just before Christmas!
I hasten to add that it was for a non-Scott application. My Matchless V twin had suffered overheating problems for some time and the penny had only just dropped that, apart from the fact that 50degree twin sparks are marginal even when new, when the cam ring wears you can get 15degree variation in ignition timing between cylinders!
A new cam ring didn’t seem to be an option so, after reading about Roger’s experience with the BTH, I contacted Tony and he kindly made me a platform-mounted version based on the design he makes for Vincents.
My early experiences are posted as feedback on the BTH website but, suffice it to say, it does everything that BTH (and Roger) claim, and the Matchless and I are very happy with it, auto advance and all.
I believe the main problem with the auto advance stemmed from magnetic interference. Single cylinder, fixed-ignition versions of the BTH incorporated the CDi unit into the body of the mag, the new version has a separate CDi which, on the Matchbox is easily concealed under the tank.
Interestingly enough, the new German “magdyno” uses the same arrangement so I suspect they have discovered that problem as well.
My 1939 FS has been performing well this season (always a worry to us “glass half empty” types!), until last Saturday when the mag failed on the way to a local VMCC afternoon run.
BTH don’t currently produce a magdyno replacement, I did consider the German unit but, for now, I have dispatched the offending item off to my regular repairer in the “Steel City”. Scott magnetos and magdynos do have a pretty torrid time of it at engine speed so I shall certainly be keeping an eye on modern developments. With self-generating types like the BTH you can of course revert to the original arrangement if you get an attack of “originality”!
Malcolm
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