Finally got to do it today.
This is on a standard '59 GoldFlash, engine rebuilt and run in, tappets checked.
New Amal monoblock 376/17, 1 1/16 dia, Pilot jet 25, Cutaway 3.5, Needle jet 0.106, Main jet 250, Needle position 3
The only thing non-standard about the carb set up is the main jet which is one size up from the standard 240.
The other changes from standard which might affect carburation are, its got a pancake filter and straight though exhausts, i.e. no baffles.
The analyser measures CO2 from which the air/fuel mixture can be deduced. The ideal mixture is about 14.7 : 1 for petrol engines, that being the point at which the amount of air entering the engine is exactly sufficient to burn all the fuel (Ethelred the expert, having read the manual
)
I Used the Amal tuning guide as the basis for the tests.
At idle I could see it was running a bit rich, sounded fine, ticked over fine, you'd never have known by ear. I adjusted the primary air screw to get it just right. Didn't sound any different. It was amazing how much change in the idle mixture a very small turn on the screw causes, an eighth of a turn is significant.
Throttle open 1/8 to 1/4 where the cutaway controls the mixture: mixture still spot on.
Throttle open 1/4 to 3/4 where the needle controls the mixture: mixture's gone a bit weak.
Fully open, where the main jet controls the mixture: mixture spot on.
So I raised the needle a notch and tested again and now the mixture is spot on across the range.
It does ride better now, more responsive, but frankly I'd never have known it could be improved, not having had much experience of A10s.
It does demonstrate that even relatively minor changes from the standard set up can affect the mixture and require carburation alterations.
