Mick.
First of all the power head is designed for a particular volume of air to be passing over the cooling fins.
Running even a little slower means a lot less cooling is is an expidential type of curve.
Running slower does generate less net heat but it also ends up in different places so your crankcase runs a lot hotter than it is designed to.
The jets in your carb are of a fixed size and designed to flow a particular amount of fuel into the engine as a fuel / oil mix.
Adding more oil means you are getting less fuel than the engine is designed to work with and that is before you you start playing with the jets.
So all you are going to achieve is a lot of carbon build up on the piston & head which nearly always ends up breaking loose at the exhaust port , getting stuck on the ring and scoring the bore.
If the smoke bothers you then switch to a synthetic low smoke oil at the same mix ratio as the machine instruction tell you to run.
You really are your own worst enemy.
Running a thicker mix does absolutely no benefit to your engine in any way shape or form.
I run all my blue smoke stuff at 50:1 and my FS 35 is better than 30 years old and never missed a beat,
Only thin replaced on the engine has been the fuel filter & lines and mine does about 20 hours work a week, every week.
The Chainsaw is the same age and again working flawlessly.
Never touched the carbs on either other to adjust for unleaded and of course change the filter, very regularly.
8 stroking is really a 4 stroke engine term.
It means missing due to richness generally accompanied with some black smoke.
I really do not know why you are here as you obviously think you know more about how to care for and use your trimmer than the engineers who designed it and I shall sign off and leave you to your fate.
Just one last thing, all the lawn care people I know use an Atom to do the edges except 1 who use a tilt a cut because they do actually cut dead strait edges.
Good luck.
* stroking
