Retarding the Ignition Timing on a P1800S

[DaveG38]

I have a P1800S, which is fitted with a Broquet catalyst in the tank, and which has run well on unleaded for the past couple of years. No sign of valve seat recession yet!! Recently, I had some running problems and as part of the overall work to clear them, I replaced every part of the ignition system. The problem turned out to be some dirt in the carburettor float chamber valves but thats another matter. Anyway, the result of all the ignition changing has been to suddenly introduce some pinking. A check on the timing showed that it was running slightly advanced, and I re-tuined it back to the correct figure. Unfortunately, this hasn't cured it, and I guess I need to retard the ignition slightly to allow the engine to run on unleaded.

Finally, the question on which I need some advice. How far would I expect to retard it? I don't really want to spend a long time changing it slightly and road testing for an optimum figure. A best compromise will do, as the old girl is only used for short journeys at lowish speeds, so performance isn't too critical. Is a typical figure one or two degrees, ten or what?

[Andrew (UK)]

When I asked about this on my 240, I was told it might need a couple of degrees of retard to prevent pinking. A slightly rich mixture will also help.