Tip # 17-Just in case it an exhaust flow problem, hook up a vacuum guage and slowly keep speeding up the motor and see if the vacuum gage gradually goes to zero. Sometimes even carbon deposits in the muffler can cause restriction. If mouse nest or carbon is suspected, lean the complete exhaust system, outdoors of course, on a 45 degree angle, wih tail pipe up. Slowly pour diesel into tail pipe unil it trickles out header pipe. Light the diesel at the lower end with a piece of newspaper. Once lit, it will "draw" like a chimney. Keep adding diesel from upper end until the whole thing is glowing RED! Cool it off and put it back on.
Roar the engine & you'll be surprised how much soot, scale & crap comes out that has accumulatd for 80 something years!! A friend did this and increased top speed from 52 MPH to 62 MPH! It's kinda' like when we're sluggish and have to resort to a laxative! Bill W.