Motorcycle Repair: honda motorcycle running on one cylender, honda cb350, air fuel mixture

Question
ok, here's the thing. i inherited my honda cb350 ('73) from my brother last summer. it ran great when i first got it and then stopped working for reasons i'm not sure. my other brother who was living with me at the time did some work (unexperianced) but never got it running and never told me what he did. just a few weeks ago i tried reviving the bike, unable to get it started. i picked up a repair manual and adjusted points, timing (the bolts holding the timing plate were gone for i don't know how long--probably the reason it stopped running in the first place), valves and valve cam tensioner, but the bike wouldn't start, but would backfire every 15 or so cranks. i then found that the timing cam was 180 deg. off (my brother?) and fixed that and the bike came to life... half of it, anyway. the right cylender runs, but after running a while i removed the spark plug to find it black with carbon (rich?). but try as i might i can't get the left working. i have noticed while turning the engine with the alternator bolt the left cylender will make a hiss noise on the compretion stroke, but compretion tests have revealed 140 psi in both sides. i think (from my unexperianced point of view) that the carberatour might be to blame. anyway, that's all i can explain about the bike. thanks for any help.

Answer
Hi Nick,

Cylinder compression is very good at 140 psi.

If the ignition timing and point gap is properly adjusted, consider cleaning and tuning the carbs. I suspect they are the problem. Ensure fuel is reaching the float bowls and are at proper levels.

Black plugs means overly rich air-fuel mixture and may be from choke use during starting.

The float bowls should not have any kind of contamination inside them. Gas changes to a gel like substance, and eventually a powder/crystal like subatnce. This process is known as varnishing. Check that the jets and passage ways are clear.

Send me an email address as requested. I'll return repair files that will assist you with repairs.

Respectfully,
Mark Shively