Lawn mower hunting/surging

[Hpd]

That's correct it did seem to behave at high speed. Awesome I'm going to follow your instructions and hopefully get somewhere

 

[Hpd]

Making some progress! Ive figured out that 1 1/4 turns works best like you expected and that the idle must have just been to low. If I have it running and slowly loosen the idle screw it stays nice up until I get to a point and then it hunts badly. Perhaps I just need to keep the idle speed up more than i had thought?

Also... When I start the mower from cold now (after leaving it a while) it does hunt but only for about 10 seconds and then levels out nice and even. I guess this is a good improvement so just leave it at that?

Thanks again for all the help by the way

 

[Burnerman]

As you undo that idle screw, the mixture gets too rich and the engine starts to hunt.....eventually there will probably be some black smoke coming out of the exhaust. My technique is to turn the screw back in until it stops hunting - this gives good throttle response once you open the throttle from idle.
Until the engine has run for a few seconds, ignore any hunting....what happens here is that once you press the primer bulb (I assume your motor has one) a blast of air is forced across the top of the emulsion tube. In turn this causes a drop of raw fuel to be blown into the engine to hopefully give you a cold start. This is somewhat hit and miss and its very easy to overdo the priming!
Its very important that the gasket between the air filter and carb is good, as air leaks here do prevent cold starting.
Well done for your efforts, its been a pleasure to be of help!
John