E: Engine Comet elect coil ignition make and timing?

[BigEd]

I’ve no idea if this applies to Thorspark but some electronic ignitions revert to full advance even at kickstarting speeds if battery voltage is low. This could cause your kickback?

The old Boyer system used to revert to full advance if the voltage dropped below around 10V. (Beware starting with a low battery voltage!)
The Thorspark system has no electronic advance, it is just an electronic trigger. It fits in the end of the existing magneto so advances using the mechanical ATD or the lever on the handlebars if it is manual advance magneto.
Tom's ignition probably just needs retarding a degree or two.

 

[vibrac]

Yes thats where I came in above my guess is it was set at the old book of 38 degrees not 34

 

[clevtrev]

Hi Trev I have a timing disc that I use for static timing, but would not be any good with the engine running. The one you suggest would be brilliant if only I could find one. many thanks

I haven`t made any for over 20 years, but would ask, what`s the means of adjusting the mag with the engine running ?

 

[roy the mechanic]

I would be inclined to look at the a t d first. To ensure it is retarding fully.

 

[vibrac]

As I understand it the suggested range is 4 deg before TDC to (or from) 34deg BTDC, so thats 30 degrees which equates to 15 degrees on the ATD. I guess old ATD were set at 17deg and I believe Mr Price had started to reduce it to 16deg before he died, what a new one has now I have no idea.
All a bit academic for me, I have a BTH its curve seems to be ok for the road although we are going for a more sophisticated system that allows the map to be altered on the racer

 

[Bill Thomas]

I think on my Rita.
You undo the centre bolt.
And put the cam where ever you want.

 

[John Reynolds]

As this query relates to a Comet (where the primary chaincase can quickly be removed), I would suggest that the easiest and most accurate way to check the ignition timing is to fix a pointer to the inside of the primary chaincase with a corresponding reference mark on the ESA - see attached photo. The photo is of the ESA which comes with the Alton electric start kit but, with a bit of ingenuity, this could be done with the standard ESA.

 

[tom wilson]

I haven`t made any for over 20 years, but would ask, what`s the means of adjusting the mag with the engine running ?

Hi Trev as far as I can see you slacken the centre cam screw and turn the cam (that is what it says on the Thorspark info site). (They also say timing can only be set by strobe light). That is the only way I can see without withdrawing the mag gear. Do you have a spare disc & adaptor, if not can you make me one? many thanks

 

[Bill Thomas]

This is what they do with Rita !,
They give you a small tool , The width of the distance between the spike of the cam and the pick up.
But mine has NO ATD, So all in the magic box.

 

[johncrispin]

Tom,
I have one of these on My Rudge Ulster with a BTH KD1, I could not afford another Modern BTH
( although available) so had to use this . They are designed for use as your other respondents have said
with retention of the manual advance, and also stipulate use of a strobe light to time it..I did my best with it by using a strobe lamp and a large timing disc statically .
Just guessing but with your Comet would it be worth timing at 4 deg adv with a degree plate and if you ATD is ok you should have correct advance. Obviously then check again with the wedge in the ATD to see the angle it fires on full advance.
If you speak to them they are very helpful. I am pleased with mine.
One of our sw section chaps has one on his Comet and he let me have a go on it the other day , its a lively beast .