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Discussion Starter · #1 ·
Was out riding my 350 yesterday. I was pushing the bike rather hard, misfiring starting at 70mph in 5th. I was able to get the bike back home but was unable to get over 50 mph and it was sputtering like crazy.

I readjusted the points and that didn't help. I am now going through the electrical and experiencing some strange test results, hoping I can get a little insight here.

Right cylinder will start and run but will misfire with throttle.
There are no starting/running issues with the left cylinder.

If I put left-side plug wire on the right spark plug it will not start.
If I put right-side plug wire on the left spark plug it will not start, lots of backfiring through the exhaust.

I will leave comments with further test results. Any help is greatly appreciated.
 

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Discussion Starter · #2 ·
I have now swapped the condensers and coils.

The right-side cylinder (with left coil/condenser) will not start the cylinder.
The left-side cylinder (with right coil/condenser) will not start the cylinder.
Bike will not start with this configuration with both plug wires on the spark plugs.
 

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On a 180° twin, you can't reverse the plug wires - that changes the spark timing to opposite of what each cylinder needs to fire on compression stroke. You can swap coils from side to side as the coils themselves are the same, but the points for the respective cylinder - left to left coil, right to right (no matter which side the coil was originally on) - have to match up for the ignition timing to be correct for each cylinder to fire at the appropriate time
 

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I'd load check the battery to make sure it's charging. I put a volt meter in my tank bag and watch while riding. Battery's will hold a surface charge and that's a good way to check for me.
 

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Discussion Starter · #6 ·
Faster, I think you're right. I put coils and condensers from a non running cb I have it's running much better but still misfiring. Maybe the main or primary is clogged and causing coil to burn out?
 

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Carburetion aside, the mixture isn't going to damage one of your coils... totally separate systems. Too lean for too long could ruin a plug (but would likely ruin a piston before that if you were running hard) and too rich for too long would foul a good plug
 

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Discussion Starter · #9 ·
I have not yet taken the carbs off, will do that later this evening if needed. I found the motor to idle best at 1/2 turn out on the fuel screw on the right side and 1 full turn out on the left side.

I took the bike on a short ride. It was riding smooth with no misfiring or bogging down until I came to a stop. I downshifted as I normally do and when I proceeded to 45 mph there was some bogging down so I turned back.
 

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Again, what do your spark plugs look like?
Try plug chopping right at that moment you’re experiencing that bog down - that would give a decent indication of what might be going on. So, if your plug, whichever side is either wet/fouled or white/bone dry, you know you are either running rich (probably worn o-rings or mains not properly seated) or lean (something clogging your passages), respectively.

Let’s see a pic of your bike. I’m not sure we even know if you are running a stock air filter or pods setup...


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Do a compression test and a leak down test... I'm betting a possible head gasket or valve seat.
 

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I recently fixed a friend’s CB360 that had a similar condition as yours with misfire. The bike was only firing on the right cylinder; meanwhile, the left side exhaust was not even warm to the touch. I checked the plugs, and they were wet with fuel. Checked compression, and that was good, even with the right side. What’s left? Spark. Well, it turned out that the points connector on the left was bent in a funny way that made it ground out on the cover. I bent it back away from making contact, and voila, we got fire on both left and right.
I hope yours can be just as easy a fix.


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