I have a Qualcast Classic 35s - which refuses to run properly. The symptoms are as follows, it will start and run nicely on tick-over, but as soon as I try to increase the revs the engine will either start to "hunt" or cut out all together.
My theory (from past experience) is that all is fine while idling, but when the throttle is opened, the main jet kicks in, and the mixture leans out - the governor then reduces the engine back to tickover, and the cycle starts again.
Normally, I would tweak the main jet mixture at this point - but the carb has a fixed main jet

I am struggling really hard to find any information about this carb (It has Dellorto FHC20 stamped on it) does anyone have any information that might help me further?