Strange Stag Misfire

[MikeParker]

do you apply the vacuum with one of those hand pumps?

M&M
I used a syringe. Perfect for the amount of air and vacuum levels you need. The connector on the syringe was the perfect diameter for vacuum hose. Not sure if that is standard? It was a 50 ml syringe I think, buried somewhere in the garage.

[richardthestag]

Definitely! I have a special test rig, on which I have tested quite a lot of dizzys and it's shocking how many have the problem of unstable mechanical advance. It's not that easy to spot but some are so bad they cause a really bad engine response when revved up. I sent a small batch to Dizzy Doctor, and he confirmed the problems, and fixed them for me.

So anyone with a mysterious badly running engine should consider this a a possibility.

This is my theory Chris, the distributor didn't come from him originally btw.

There is definitely something amiss with mine in the 3k rpm range. after driving for lets say 20mins at constant revs the engine starts to generate a lot more heat. decrease to 2500 or increase to 3500 and the issue goes away.

I have done the usual checks with the strobe but using the timing marks on the front of the engine requires some accuracy in the location of TDC and the test equipment of course. Plus you need to extend the range. not easy when the graduations are fixed.

[Wheelz]

The problem is difficult to spot on an engine with limited access, and engine noise. On my test rig such a problem is noticeable as a blur on the strobe disc, plus a change in sound, like a bad vibration at certain revs. The good ones sound smooth all the way up the rev range.