Exhaust "popping" on overrun?

[Chris KC]

Funnily enough only yesterday I adapted a later action plate marked 17 degrees - I agree an insert would have been a nice solution, and I did consider sleeving the pins instead of altering the hole; but it responded fairly well to a dab of MIG on the outboard sides of the holes, which was then ground flush and gently filed to give the desired amount of advance; in my case I settled on 8.5 degrees and got it more or less by sheer luck at first attempt. I used a DTI on the rotor arm to double-check the actual amount of advance.

One observation I would add is that I have stripped a number of DK4A's which have at some time been re-bushed; but have yet to find one where the oil supply hole had been re-drilled through the new bush!