I've been playing about with my 'VH' again . . .
After fixing the tank, machining the barrel top face to fit the head without a copper gasket and fitting a 7.5:1 piston I had it running with a re-built MO1 Mag that had a 'Brightspark' condenser. The Dynamo is now running at 12 volts and the bike has been re-wired Negative Earth with a "Dynamo Regulators Ltd DVR2" Regulator. It has LED bulbs.
I had it running but starting wasn't good. When it ran it felt good with plenty of poke. It has a 28mm Concentric with a 200 main jet.
Then I stripped the Concentric down, put it through my Ultrasonic Cleaner and re-built it with some new parts and gaskets. At the same time I removed the points assembly from the Mag and fitted a 'Thorspark' Electronic Ignition System (it has a coil and a keyed ignition switch but still uses the manual advance/retard).
The 'Thorspark' set-up has an alloy rotor in place of the points assembly and a solid-state pick-up mounted where the face cam fits. The rotor has two magnets (?) at 180 degrees - presumably for balance. This will produce a 'lost spark' on the exhaust stroke.
Timing is a bit hit-and-miss. There is a felt pen mark on the static part and this is aligned with a magnet on the rotor when at full advance with the piston 5/8" before TDC on the compression stroke. so far so good.
On starting, the exhaust note is extremely loud, it won't run cleanly or tick-over (despite playing with the throttle stop, air jet and the height of the jet needle) but it feels to have great potential. A neighbour, who has the same Thorspark set-up on his 3GL Matchless, is saying "There's something not right there, but I can't decide what"
I have adjusted the timing (by rotating the rotor a little at a time) but it doesn't improve. I'm now thinking that the lost spark is the problem and its that which is causing the very loud exhaust (the basic motor hasn't changed since moving from Mag to Coil ignition).
My next step is to rotate the rotor 180 degrees in case the magnet polarity is critical. The little magnets may well have he same polarity as they are set axially in the rotor, so this may be a waste of time. Removing one may be the solution.
Has anyone else been here and have any pointers (apart from "leave the B thing alone, Ariels knew what they were doing"
Bob (striving for perfection).
My avatar shows the late Len Rich in 1970 with the bike I now have - a 1958 Ariel VH