Re: Tacho problem

[Mike Wattam <101714.1343@domain.elided>]

David

Yes, the tacho will definitely go intermittent if the spark is not
happening reliably.

Gap correctness is essential as there is a very small dwell angle. 
However, this is in vain if the dizzy is badly worn, e.g., loose spindle,
lateral movement in the base plates etc., as this will cause the dwell
angle to disappear some (or most) of the time.  Therefore do check dwell
angle very carefully with the motor running.

A secondary cause can be high resistance in the HT leads or bad plugs.

I presume from your elecrical knowledge you have checked resistances
throughout LT side of ignition, including on the starter itself.

Mike Wattam
Triumph Stag Register