Forum

[Adrian]

Mechanical advance and retard with this particular electronic ignition, Jamesy, like me you didn't read the previous posts properly.

[Rattlebattle]

So, perhaps the a/r isn’t working properly (eg weak springs) allowing the timing to be fully advanced when it should be retarded? Have you tried removing the spark plug, earthing it and gently turning crankshaft to see if the spark is roughly where it should be?

[Chris Tindal]

It's working again Rattlebattle. It's not very satisfying as I don't know why, but that awful kickback has gone. All I did was charge up the battery and it stopped but I don't think that was the reason. It must have been linked to the carb top unscrewing but I don't know why it carried on for a whole day with the top screwed back on tight, it remains a mystery. I checked the oil pump spindle last night and it looks as good as new so no damage done.

[Count Johnny]

Could a weak spark cause it?

[Aethelric]

Just a thought - the thorspark also works on twins where it works on the "wasted spark" principle. Are you getting a spark on the exhaust stroke?
There is a post here

http://www.britbike.com/forums/ubbthrea ... ber=677738

from someone who removed a magnet to eliminate it. Also lowering the current consumption.

[Citrus]

I have had the same problem with my bighead. Weak advance /retard springs was cause. Replace them.

[Chris Tindal]

Thanks for the replies, all seems well now but it's worth looking at those springs anyway. Citrus I'm trying to compile a register of surviving Bighead bullets. If you still have your bike and are willing to provide some details of it, contact me on [email protected]