Nothing wrong with using a tach if that’s what you have to hand. It’s actually a good way to get you close and safe. The issue arises when you:I'm pretty much stuck with tuning by tach, as I can't hear very much, and I'm not willing to lose more hearing by running my saw with my hearing aides on. Unless one of you guys wants tp come to southern oregon and help me?
1). have an engine that doesn’t have rpm specs. Typically cheaper equipment or old equipment, that’s when sound and feel are handy.
2). When the ignition coil lead has some means to suppress emf and you can’t get a good reading