Does anyone here have experience doing this? I have a 2 blade mower with a single cylinder 16HP Briggs engine that is over 20 years old. The faster I run the engine, the faster things break from vibration and poor design. One blade unscrews and the other tightens because of the way the belt drives them. Keeping the blades sharp helps, but slowing the engine down helps more.
From videos I have seen, the usual fixed timing is about 25 degrees before TDC. If I could make that 20 degrees BTDC the engine would have more torque at a lower RPM. When mowing, torque matters more than instantaneous HP. I do not like running any engine above 2/3's max for any amount of time., esp. a mower. Speed kills when parts fail.
A new machine would cost about $1700 at Lowes, and I don't have that kind of money to spend right now.