1974 CB 360...only firing on 1 cylinder

[wrenchwench]

Hey all....I've done so much work to this bike...rebuilt the carbs, new plugs, plug caps, new points and condensers, new air filters, coil is good...etc. If the bike is idling really high, both cylinders will fire, however, once I drop the idle down...the left cylinder dies out. There is a small hole in the exhaust...? Also, I can only get the left cylinder to fire by turning the idle mixture screw out over 3 turns...which is excessive! Any suggestions???? thanks.

[redcoat]

I absolutely hate problems like this.

I ussually throw my hands in the air and take it to the old man at the dealer who will work on old bikes.

However: It's a twin, so it's only one side or the other- and you know the problem is with the left side, and adding lots more air, via the idle jet adjust, it runs. It seems to me it;s saying that it's getting an incorrect mixture. More air via the idle makes up for too much fuel. That could be caused by a low speed jet that was too big- maybe you exchanged the jets with each other (I've done it), or the float is set too low, or half sunk anf the carb is being partially flooded.

Persoanlly I'd go with the easiets first: Check the size of the jets: check they are in the right holes. The I'd take it to the shop, spend the few hundred, and be riding in a few days, rather than aggravated for weeks.

Let me know how it goes, I'm genuinely interested. I hate anything more advanced than dunking carbs in cleaner and replacing jets.

Justin

[wrenchwench]

problem is that it's a customer's bike...I work on bikes here and there...not a full time gig. sooooooooo, can't really take it to another shop,...and there is NO dealer that will work on old bikes in the area! I'll double check the jet size....and mess with the float level. Thanks. I'll let you know how it goes!

[ghost4life]

hey i have seen the same thing happen on a friends cb 350 it turnd out to be low comprtion on the one cyclinder rigs went bad or were stuck i cant rember hope that helps

[Fargo360]

I'm having the same problem with my 360T. Same cylinder, same problem, only mine won't run on both cylinders when I rev, just the right one. I'm interested in seeing what fixes the problem because I'm in the process of rebuilding the carb.

One question I have: On my bike the plugs are sooting up real bad, real quick. Is that bike doing the same?

I'm feeling the pain of no one that will work on my bike too. No dealer in town will touch it and the general bike mech guys tell me its easier if I just fix it. Kind of aggrevated. Anyhoo, if you find out what is causing that to happen let us know! I will stay tuned.

[insaneman_12]

First check the points gap at time and the timing of the points on #1. Then if that is not the problem check the carbs. Paticurally the rubber on the slides because they are a cv style and then synicroise the carbs. Make sure when you clean the carbs clean the passages though out the carb too because I see that problem time and time again. You can clean the jets all you want , but if something is blocking the passages nothing will get though. Hope this helps.

[Fargo360]

My 360 is still only firing on one cylinder. I cleaned and rebuilt the carb and put in new plugs. It seems like it runs better than it did before, but still only on one cylinder. When I try startinging it, every once in a while it makes this spitting or snapping sound, but not from the exhaust. If I spray starting fluid into the air intake of the inoperable cylinder it throttles up, but only for a second. I don't know. I'm really starting to get pissed at this bike.

Also, I think the bike has an alternator problem. Seems when I bought my bike it started on its own no problem, but within a couple weeks the battery was dead enough that I had to kickstart it. After having it on the charger it started on its own again. But after about a week and a half, could barely kick start it.

Now after I've cleaned up the carb, it runs fine on one cyl., but the bat is dead and I have to kick start it. Runs fine for a good long while, but doesn't really get the battery charged. Is the battery bad, or is the alternator going? Like I said, I'm starting to get pissed at this bike.

[mydlyfkryzis]

Synchronize the carbs. At a slow idle, one carb butterfly is completely closed, the other cracked. Got to get them both cracked.

[Fargo360]

They are both sync'd. I made sure to do that when I put them back together. It doesn't matter how far I open the throttle, only one cyl. runs.

[BuzZz]

How is the ignition system? Try swapping the spark plug leads from one cyl. to the other and see if the problem follows the lead.

If it does, then you may have a bad coil, bad high-tension lead or bad boot.

If it doesn't, the cold cyl. may have mechanical problems, like a bad/busted valve or piston ring. Have you done a compression test?