305 scrambler running too lean

[1966edward305]

can anyone tell me the stock main jet size for my 1966 cl77 honda 305 scrambler and how to fix the bike from running to lean? thanks eddie

[rbaselt]

The stock size is 120, but that's assuming baffled exhaust and stock air filters. You can try raising the needles by one notch at a time and checking the plugs after each change. Make sure your plugs are the correct heat range (I use D8HA). If you are still too lean, go to 125/130/135 main jets in a stepwise fashion. --Randall

[1966edward305]

hey randall, thanks for your help. i sent you a private reply. look it up, eddie

[rbaselt]

Eddie,
Right, you definitely don't want to be lean with straight pipes, you'll burn the valves. You will probably need 130 mains. The backfire is most likely a slight difference in the timing between R & L cylinders. Be sure to use a strobe timing light to check both sides after doing the static timing. But if there is uneven wear or different spring tensions in your advance weights on the camshaft, you'll never fix it with timing adjustments. --Randall

[1966edward305]

hey randall, read your help response and am excited. will show your posts to my mechanic and hopefully, he can do what you suggest adaquately. i ordered 130 and 135 mains from ohio cycles. i have the correct plugs. interesting note to you, the backfire is only coming from the top pipe (left cylinder) maybe you have something there about incorrect timing on both cylinders! i hope its not in the camshaft, don't really want to go there, if you know what i mean..........lots of work....... thanks, eddie........P.S. can i keep you posted on my progress?

[1966edward305]

hey randall, had the bike worked on today. tuned carbs and timing, checked plugs for type of burn (they were a normal light brown, not white and not black). adjusted carb floats. had the main jets changed to 135. this improved performance at low speed, however when i got the bike up to about 65 mph, it began to sputter and would not accelerate anymore. i raised the choke lever and at about 3/4 raised, the bike would give more proper performance. should i put 140 jets in or raise the needle clips in the carbs one position. i still think the bike is running a little lean, however, it is better with the 135 jets. also, the backfire is gone at low speed but is loud when i let off the gas at 60 mph and am beginning to downshift thru the gears till it finally disappears at about 30 mph.........thanks, eddie

[rbaselt]

Eddie,
I would recommend addressing the timing issues before changing anything else on the carbs. It sounds like either your two sets of points need to be better synchronized or the advance mechanism on the camshaft needs attention. --Randall