About a month ago I decided to try again to tune my Mikuni's. I have been getting pitiful gas mileage, ( 19-22) for about the past year at least. I have tried different needles and positions and richer/leaner etc. with the different positions. Never could get it to run well and not run rich.
Anyway, a month ago I just ran the mixture in full and then backed out 1 1/2 turns. Since then I am averaging 26 if I am "on it" a lot and if I run around 65 - 75 I have averaged 30mpgs! I must say I do almost all highway driving, very, very little around town. I drive about 500-600 miles a week and have double checked my figures over several tankfulls at the same station, sometimes same pump for the last month.
Earlier in the week I had filled up my tank untill it was spilling out of the top of the neck, (easy to do in a 142, on some pumps it doesn't seem to cut off untill it reaches the top, but this time I did it on purpose...I know not supposed to), then yesterday after 399.9 miles and an almost empty tank I did the same 13.272 gallons. I have previously checked my odometer against the mile markers and it is very close so I am going to call this "a good reading...or close enough".
I may be running a little too lean as there is a flat spot when accelerating from a stop. I heard this is a Mikuni trate but I hate the pause, so I pull the choke out about 3/8" then push it back in when I am up to speed. I checked the plugs a couple of weeks ago and they are overaqll a very light tan.
Wooo Hooo............for now.