Topic: backfiring from one cylinder on a cb350g, the other cylinder runs great

[griffin]

the bike sat for a couple mmonths and now left cylinder won't fire won't at all except to backfire occasionally. is this probably just in need of a complete carb rebuild? i sprayed a bunch of carb cleaner down the venturi and took the slide out and cleaned that but it is still doing it.
i also checked the compression and that was about 120 in each cylinder, which is pretty good, right?

[mattcb350f]

Well griffin, this is an all to common problem with bringing an old bike back to life. The issues to cause this can be numerous but you've already started to narrow it down 
Compression is good and even on both cylinders and if it's backfiring than there is some sort of spark.
Check to see if there is good consistant spark on the missing cylinder, if not my guess is the points need to be cleaned on that cylinder and adjusted.
If you've got good spark, than take the carb off and give it a good cleaning. Check to make sure that every jet is open and that the float needle functions properly.
Now, with a good carb and spark and compression, it should work 

Those are the usual suspects but I did work on a 360T once that had a bad coil that would cause the same thing intermittently.
 Matt.

[Killer Canary]

Mine did the same thing and I tried a few remedies at once so I don't know what actually fixed it but here goes:
1) only a few strands were left  connecting the wire to the pointset.
2) vacuum leak between boot and the head.
3) float height was out, should be 26 mm.
I first measured compression, set valves, c/chain and timing, soaked carbs and replaced all rubber and it fired willingly on #2 but I needed to do these other things to get #1 banging.
Keep telling yourself it's nothing major( which it isn't) and you'll find it.
This thing hasn't run since '79!

[mikedialect]

good points above.

As I say- Mind the points. Check for that fire. I've had some weird problems where it was being grounded in the switch, but it's not likely that is what is happening. Run a points file over the points to clear any of the crap off. If that doesn't work go after those plug boots. If still nothing check the coil (I've never had a 350 coil die on me, YET). Then the valves. It's pretty easy to check to see that you're getting fuel, but the above ignition stuff is ofter the culprit.