What is the maximum rpm's for my riding lawnmower? I have a 23 year old Lowe's 45" cut, 18 hp Twin II vertical drive shaft with horizontally opposed pistons. I estimate the engine has been run 1000 to 1500 hours. It sounds as if the engine is running too fast and/or loud. How do I go about adjusting rpm's on this engine?
Most of the older opposed twin engines ran between 3000-3400 RPMS. The real old ones ran at 3600 RPMS. Do you have a small engine tachometer, you will need it. Most are adjusted by locating where the throttle cable is attached to a mounting plate or the carb. You will loosen the clamp and pull back on the cable pulling the the throttle butterfly open further.
Rivets explained how to set the throttle control, but the actual engine rpm is set by bending the tang that the governor spring hooks to. You will still need a tach to see what it is turning. Most likely noise may be caused by either a bad muffler, getting burned out, or possibly a blown exhaust gasket.
