faulty flywheel

[lofty]

Hers an interesting one..

scooter wouldn't start.. no spark
regular 'indian/ducati' type ignition system

did the usual:
plug
cap
HT lead
disconnect ign switch wire
different CDI
checked resistances/earths on stator-- all ok
had stator out, changed LT coil anyway
tried different stator
all still no spark

scratched head a bit, found another (full weight) electronic flywheel in the 'parts cache' tried that, hey presto a spark..
original (mid weight) flywheel looks ok, and magnets are 'magnetic'..
thought maybe pickup height, so fiddled with that, still no spark on original flywheel, but ok on substitute one..
I can only conclude the flywheel is the problem.. but why?
any thoughts?

[Scooterslag]

The magnets have been damaged some how but for all intensive purposes still magnetic? Paul

[Adam_Winstone]

Air gap? This is the distance from pickup trigger fingers to the corresponding magnet triggers.

If this gap is too big then you can run into problems. I believe that Anthony Tambs posted info on social media about how to adjust.

[MickYork]

Would be interesting to fit an external pick up and see if it works.....

[lofty]

sorted..

Adam was 'on the money'..

gap between pickup and flywheel 'fingers'.

I carefully bent them ever so slightly inwards and hey presto, it works..

it must have been so marginal as i only made a very slight tweak, i would say fractions of a mm..

thanks for the input all..

[Adam_Winstone]

Thanks for the feedback, which may serve to help others in the future too.

BTW the Antony Tambs suggested adjustment method is to slightly oversize the hole in the laminates that the small locating stub/post on the bottom of the pickup fits into, and slightly enlarging the hole that the screw go through to lock the pickup in place. The increased clearance for these 2 is enough to allow the pickup to be moved slightly forwards/backwards to alter the air gap.

However, interesting to hear that you managed to bend the trigger fingers fractionally; enough to result in a signal being delivered. I don't know how brittle said trigger fingers are but glad to hear that it worked ok.

[Fast n Furious]

Check for wear in the mag side bearing by grabbing the flywheel and lift it up and down. If you detect knocking then replace the mag bearing.