Posted by Max on July 14, 2003 at 07:11:07:
In Reply to: Improve gas mileage ? posted by Mike on July 14, 2003 at 06:49:06:
First have you read the plug for mixture. 2nd is the exhaust opening on the Jardine sooty, if so your probably need to put 1/2 the spacer thickness back in and try again, maybe even the spacer (hope you saved it) if you live at altitude over about 300ft. Fine tuning a single cyclinder engine w/o a dyno involves reading the loug at various engine speeds and loads and adjusting that part of the carb meeting devices to dial it in closer.
Reading the plug has to do with the amount of carbom on the base of the insulator and lower part of the outer shell. Will need a good light and magnifying glass maybe. Nose of the insulator is a good place to start tightening up the fuel and then read it lower. run the engine say 40 in 5th level cruise, for about 1/2 mile, pull in the clutch and flip the stop switch together allowing the engine to stop without running on the idle circuit. Carefully, it will be hot an can pull the threads, remove the plug and read it. change one thing and then make another run. I'd suggest removing the LH chrome cover so you don't have to pull the tank everytime and have a plug socket that will retain the plug for removal and reinstallation. Put the cover back on when you are through. Carl Shipman wrote a great book published by H.P.Books years ago, Tuning for Performance that detailed all this. Try to find it at a library or used book place. So old is doesn't have an IBSN. Pub date 1973. Haynes also has good carburetor book that is more recent. Happy tuning Max