Thorspark Electronic Ignition advice.

[Mike Nash]

Dennis,
Can you do it by attaching the disc to the end of the camshaft? It's half engine speed, of course, but I've done it that way to make plots of valve lift. Not run the engine like that but I suppose with care its possible.
Regards from MikeN.

[paul.jameson]

Assuming that the Thorspark works much the same on a single as it does on a magneto equipped Square Four, you should be able to use the advance retard lever for some adjustment. This should at least give you an idea of which way to go and by how much in your adjustments. Using a strobe would be better, but I can't think of a way to use one on a single unless you put a degree disc on the end of the crank which does, as you say, involve takingthe primary side apart. That, with practice, is a fairly quick and easy job so if you need the 5/8 btdc in degrees, let me know and I will work it out for you.

[dennis.t]

Paul and Rob,
Than you for your replies. Yes the advance/ retard still works but I am still left with incremental adjustments at the rotor to get the ‘best’ starting point. If I am lucky I may not need to use a strobe light if I can find the sweet spot within the range of manual adjustment by the advance lever. I will post an update when I have more news.
Dennis

[Roger.Baker]

I put a Thorspark on my VB. I just set it up approximately so that it would run, then adjusted it until it felt right when riding. I couldn't'd be bothered to strip the clutch 3 times to strobe it, but I'm happy with it after a bit of experimentation. As you say adjusting the advance /retard as you ride works. Dead easy to adjust, just unscrew the magnet, move it then tighten up.
Roger

[dennis.t]

Roger,
That is reassuring advice thank you.
Dennis

[dennis.t]

I finally got the bike to start after much tweaking of the rotor. My 1955 VH500 seems very sensitive to small adjustments of the rotor alternately backfiring violently through the carb or the exhaust. I even contacted Thorspark for advice but they could only suggest "using a strobe". Luckily I hit the 'sweet-spot' with the rotor quite by chance and the bike burst into life and runs well. I am not inclined to make any more adjustments in case I lose the sweet-spot. I will run the bike for a while and see how it performs. The Thorspark system has definitely improved the spark compared to my magneto which my be 'tired' though it did spark.
It might be coincidental but I put a fibre washer under the carb fuel inlet/ needle holder to raise the fuel level because the spark plug seemed dry when trying to start the bike. This seems to have improved starting. On my VH the inlet manifold is tilted upwards at quite an angle so that might affect the fuel level in the carb?
Dennis