BRUCE
Carbon build up in the combustion chamber, especially seagulls, (even though BS said there was no need to de-carbonise) to me, now looking at 40-50 years of use or more is utter nonsense. Fuel quality wasn't that great, oil quality wasn't that great, and what you see now is the after effects. Modern/better fuel and oil combinations reduce the amount of soot and carbon build up. leading to better performance and cleaner emissions. (your average car these days is no different)
Various topics have sprung up in recent times on here about oils and how they've improved over the last 20/30 years.
I think i recall somewhere on here that BS even commented that you could quite safely run a seagull on used engine oil of all things? (probably after it was strained and seived) I can well beleive that, certainly during the war years and several years after that, as there was very little money about.
Even fuels have improved to some extent (perhaps not with ethanol in gasoline) and we all know what that does to your fuel lines and carb fittings over time.
I for one, would like to try and keep my seagulls running for another 50 years, with whatever fuel and oil combination might be around.
I am, and will always be a big beleiver in stripping down old engines to see how they've coped over the years. It tells a lot if you know what to look for.
P.S take a look at the piston crown whilst it's apart. (does it have any pitting on it?) like it's been shot with a 12 gague

most of my 102's are like this as well.
p.p.s any colour you like. its your motor after all? (silver/gold/black always look quite good together)
jon