Left cylinder cutting out mid-rpm range/CL-77

[CandyBlue]

Left cylinder begins to sputter mid way through third gear, badly in 4th. Unless I floor it, then it roars down the road. Idles fine. Have been through carbs more times than I can count. Super clean, original jets. The floats are cutting off flow well after fuel level touches main jet so it's getting fuel. Air screw 1.75 turns out. Slide and needle are proper size, at right height and are moving fine. Spark plug new and properly gapped. Had coil checked and is "like new" the shop told me, "functions 100%." Timing is dead on, idles fine without backfires. Just the mid range sputters, you know, the one you operate the bike mostly on!! I'm really stumped. I can't think of what next to try? Advice any of you fine people?

Further specs: Compression both cylinders 165-170 psi, gas is clean, no water. All fuel delivery lines have been checked twice and are free flowing from petcock to main jet. Left plug is black, sometimes light brown, so I can't tell if it's not sparking enough and not burning fuel, or sparking just fine and not getting fuel. Rebuilt this bike over the past two years ( I used to play on it when I was 7), Ed Moore helped me in the early stages when I was 17, the first time i tried working on it and it's gorgeous. But can't get this damn cylinder remedied. Any advice or help very much appreciated lads and lasses. Scott

[LOUD MOUSE]

Properly clean the points for the bad side. ...............lm

Left cylinder begins to sputter mid way through third gear, badly in 4th. Unless I floor it, then it roars down the road. Idles fine. Have been through carbs more times than I can count. Super clean, original jets. The floats are cutting off flow well after fuel level touches main jet so it's getting fuel. Air screw 1.75 turns out. Slide and needle are proper size, at right height and are moving fine. Spark plug new and properly gapped. Had coil checked and is "like new" the shop told me, "functions 100%." Timing is dead on, idles fine without backfires. Just the mid range sputters, you know, the one you operate the bike mostly on!! I'm really stumped. I can't think of what next to try? Advice any of you fine people?

Further specs: Compression both cylinders 165-170 psi, gas is clean, no water. All fuel delivery lines have been checked twice and are free flowing from petcock to main jet. Left plug is black, sometimes light brown, so I can't tell if it's not sparking enough and not burning fuel, or sparking just fine and not getting fuel. Rebuilt this bike over the past two years ( I used to play on it when I was 7), Ed Moore helped me in the early stages when I was 17, the first time i tried working on it and it's gorgeous. But can't get this damn cylinder remedied. Any advice or help very much appreciated lads and lasses. Scott

[CandyBlue]

Certainly will. I'll post a reply soon as I can get to it later today. Thanks!

[CandyBlue]

Took my time with a point file, ignition cleaner solvent, and an air compressor, double checked point gap and timing and I'm still having the same problem. Idles fine. When I kick it over it's instantly idling perfectly with a cold engine, I'm used to this bike being a little bit cantankerous and needing to be choked when cold, so this is a new symptom. I also checked intake valve, it's clean and free of debris and has the correct .1mm gap. Still starts cutting out left cylinder top of third, fourth pretty badly. I'll keep plugging away, and if anyone else can give me some good ideas, I'd love to hear em!

[barnbiketom]

Trim plug wire ends yet?
Check cap resistance?
I replace plug caps with non resistor.
Also swap coli leads and swap the blue/ yellow points leads to the condenser an see if the problem stays or moves to other side????

[Hoosier Tom]

After the symptoms appeared did you already try swapping plugs side to side or try a new plug?

HT

[CandyBlue]

Yep, tried swapping and later tried new plugs with same problem. Raining like a banshee here today but soon as I can get it out on the road with ends trimmed and if needed leads swapped I'll update. Thanks guys..