[Gremson]

I posted this problem originally in the electrical forum, but I'm starting to think it might not be an ignition issue and hope others might find a solution to this conundrum.
My 73 CL350 isn't firing on the left cylinder. I replaced the plugs. I've checked both side for spark and I can see both plugs spark when I turn the motor. I've reset the cam chain tensioner, I've adjusted valve clearance, I've set the timing spot on. I resynced the carbs too.
I can start the bike and it'll idle, but it's lacking a ton of power at take off. Won't rev much higher than 4k. It sputters and surges when I try to hold a constant speed.
I've noticed that after idling for a bit only the right exhaust gets hot.
I'm running out of vintage honda YouTube videos to watch! I'm lost on what to check for next. Any help is appreciated.
https://cloud.tapatalk.com/s/59a05bb19eb6c/received_10155658615611528.mp4

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[Yendor]

Have you tried spraying some starter fluid directly into the Left Side Carb Intake?

In your video you have them open for access.
If it picks up the RPM with that I would suspect Carb.

 

[-alan-]

Good point.

If that is inconclusive, another old-fashioned but occasionally invaluable aid is one of the see-through spark plug devices.

I don't know whether they are still available, but if you van beg steal or borrow one they will let you see if there is any spark or burn in the cylinder.

 

[Gremson]

I'm starting to think it could be an altitude thing. Everything was fine back in portland, and okay in eastern Oregon. But the problem happened after I got into high desert area, and reno isn't much lower.

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[doode]

Is your plug wet or dry after trying to start it?
Does your header feel warm or cold?

 

[Gremson]

Getting closer to a carb problem. I spent some time squirting carb cleaner and just plain fidgeting with the left carb and it somehow started firing and seems to be running fine now. Just went on a quick ride and no trouble.
I've taken apart the carbs, cleaned them and adjusted float height over the past few months, but I haven't done a full rebuild on them yet. Looks like that's next on my list.

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[Yendor]

Might have just gotten a speck of debris in one of the jets - then getting that cylinder to fire created enough vacuum to suck it out.