strange sparking on points, R75/5

[DeeG]

this is on a 73 R75/5, but......

Changed the points and condenser today.  Gapped the points, checked the timing with ohmmeter. Fired up the bike to check properly with timing light.  timing is good, got the 'S' at idle and the 'F' at higher throttle.

BUT.  There is this bizarre sparking at the base of the points assembly, pretty much where the lead wire attaches to the base.  

I put the old condenser back in, thinking the new one was faulty.  No change.  

Bike also has some intermittent backfiring along with the sparks.

I'm a little confused and concerned about this. I've never seen this happen before.   :-?

http://youtu.be/D_R8HRhZCV8

[Tony Smith]

Put your old points back in and see if it still does it would be me start point (pun in_intended).

[Barry]

The back EMF at the points can reach a few hundred volts so if there is insufficient insulation or clearance between the points wire and any adjacent metalwork the voltage could jump the gap.

[DeeG]

The back EMF at the points can reach a few hundred volts so if there is insufficient insulation or clearance between the points wire and any adjacent metalwork the voltage could jump the gap.

The clearance was the problem.  Noticed on my 75/5 that the wire holder (or whatever its called) that is attached to the points was bent at a 45.

Took the points out of the other 75, bent them, put them back in. Re-gap and danged if it didn't just fire up and run properly.  ~sigh~  I should have thought of that myself.