Here are the things I'd like to know for sure Paul:
1. Can you always make the engine run well, whether or not you have to apply the right amount of choke to do it?
2. Does that apply whether or not the governor is connected to the throttle?
3. If you apply that amount of choke, and set the engine at a fixed speed, is it stable? That is, will it still be running perfectly five or ten minutes later?
If the answer to all three questions is yes, it seems to me we should be focusing on making the mixture stable and correct, if possible without modifying the carburetor.
All that is based on the idea that the engine having "come good", is temporary and will not continue if the wind changes or something equally irrelevant happens. In that connection, you might try a crude and brutal trick. If you can get it to go lean again, try tapping the carburetor body once or twice with a rubber hammer while it is running, and see if that makes a difference. If you can't get it to go lean any other way, tap it and see if it goes lean.
It may be that whatever the problem was, it has now gone away forever, but I doubt it. More likely the situation is unstable. Unless we can find what the cause was, it will be a long time before you'll feel comfortable that you are going to be able to use it when you want to.
My favourite guess is that the needle was slightly jammed where it fits into the top of the float lever, and it has now come unjammed. You can help clear this up by answering two questions:
1. Had you just dismantled and reassembled the carburetor when this problem began?
2. When you put the float mechanism back together, did you gently lift and lower the float a couple of times before you re-attached the float bowl, and did you then keep the carburetor the right way up afterwards?
Question 2 relates to something you should do every time as a matter of habit. Float mechanisms are always tinpot, even back in the days when they were used on cars.
Last edited by grumpy; 26/01/15 04:58 PM. Reason: Add detail
