Sorry, not really a proper old mower but some one might have some ideas.
I bought this L38 Flymo about 25-30 years ago to do banks when I was doing mowing contracting and got it out the other day to use it or get rid of it and gave it a good clean and tried to start it. I got it started but it won't run without the choke half on no matter where I set the mixture screw and as soon as it starts running on the half choke setting, it starts to hunt (that's what I call it when the revs go up and down). It has no throttle lever, just set at full throttle.
I have cleaned the carb out several times and cleaned the fuel tank, checked the air filter etc. It appears to have a good spark although I don't have a new plug for it, I have given the old one a good clean. I feel it is a mixture issue but don't know what to do about it now. I don't really want to throw it away but am close to giving up on it.
The carburettor is a conventional one, not a diaphragm one.
Thank you for taking the time to look at this.