I use my ears on all my engines. 2 and 4 stroke alike. I have no problems. I use all of the above mentioned methods. I do have a tach. I don't even know if it works. Never turned it on.

YS engines have a lot of power. Way more than you need on a Lt-40. But they are very good engines. Should last a long time. I run 10% nito in all my engines. I also use a synthetic/castor blend. i would never use fuel that did not have castor in it. It is a safty feature against lean runs that I cannot do without. Besides I LLOOOOVE the smell of properly cumbusted castor oil. Befor anyone says it yes I am a lot warped. Good luck with your YS and enjoy it.

Mark Shuman