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Discussion Starter · #1 ·
Hey all!

This is my first time using any forum for information, and after perusing several forums I still can't seem to nail down the problem.
I have a 1976 CJ360T that was running until I began a budget brat build on it. The motor is stock, brand new Mikuni VM30's, pod filters and 2-2 high flow exhaust. I have all new ignition parts from the coils to a PAMco electronic ignition. New boots, wires, the works.
My left cylinder is running cold, even after warming up, and the right cylinder is doing all the work. I can pull the boot off the plug on the left side and there is no change, but the engine dies when I pull off the right side. There are no air leaks, and the carbs have been synced. Today, and the reason I am writing on the forum, I noticed that the inside of the left exhaust pipe had a black sludge gathering on the tip, the right side does not. I'm not sure if that was un-burned fuel mixing with the carbon in the pipe or oil. The left plug is white and clean (the cylinder not working) and the left is normal, light brownish. I swapped the plugs themselves and the right cylinder still ran with the left not. The plug on the left side is firing, and was verified visually and with a tester on the wiring.
Could it be oil in the left cylinder? Could sitting for 6 months do this? Why would the plug still look brand new when the cylinder is firing, and getting fuel?
I'm trying to do this without a rebuild, but...

Thanks ahead of time!

-Trogoloff
 

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Sounds like your left cylinder isn't firing at all (which I get, cause mine isn't right now either :p ). My problem was the PAMCO, so don't immediately assume that's a safe bet - try reversing your coils (left spark plug wire to right spark plug, left control wire (blue/yellow) to right control wire, etc.)). If it still runs only on the right cylinder, your spark's probably OK.

The mantra is always fuel, compression, spark - if you're sure your spark is good and firing at the correct time (with a PAMCO you'll need to do that via dynamic timing light), move on to compression. Grab a compression tester and check the left - anything above 150 psi when the engine is cold is decent, 180+ is happy.

I don't have any experience with VM30s, but there are a lot of good folks on here that can point you in the right direction for checking fuel delivery as well.

Good luck, and welcome to the forum!
 

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Discussion Starter · #3 ·
Thanks for the quick reply!
I reversed the coils and the right still ran the show, with nothing from the left. The left exhaust is pretty weak (with and without the coils reversed), but there was still exhaust. Could my pipe be plugged somehow? I start work again, and school, tomorrow, so my summer-time officially ends tonight. I will find an evening to check the compression. It had good compression in May, so I just assumed (whoops) that it would still be fine.
And on the PAMCO, what is the problem with yours? Good to hear it is not a safe bet...unfortunately that's why I dropped the money on it...ha!
As this is a budget bike, something to teach others how to ride on, or for my kids, I didn't want to do a tear down and rebuild, but if compression doesn't check out, then I'm afraid I may need to.
 

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If you still have the parts, put the points back in and see if it runs.
 

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I'd honestly gamble that your left side isn't firing at all - the weak exhaust is probably just coming from the 'whoosh' of the the left cylinder compressing air and then releasing it unburnt. Try to feel for temperature, if you can - if the left header is warm, then you might have partial combustion, but I wouldn't think so based on what you've mentioned; the exhaust air is also likely cold, compared to the warmer stuff coming right pipe.

I wish I knew what the problem with mine is! :( Pete can be hit or miss on supporting them. I've checked continuity on all of the wiring, visually examined the solder (that's a road I don't wanna go down) on all of the boards, and tried reversing everything; I suspect it's a problem with the left magnetic sensor.

Autozone/your local chain auto store will rent you a compression tester for free (though admittedly sometime they're crappy :) ) - Mike's got the right idea though, it's probably a quicker test to slap the points back in, gap them correctly, and see if it runs both cylinders that way.

To give you my full opinion, I'd bet it's the PAMCO you're having an issue with - I would think that you'd have enough compression to be getting at least a little combustion out of the left cylinder if it was running OK before.
 

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Discussion Starter · #6 ·
Thanks for the replies!
So an update. I went out to test everything, and the bike definitely isn't getting a spark on the left side. I started to test power on everything, and the points have power to both of them, but there is no power to the blue wire. The right coil, I get power to both wires. I plugged the old coil in, and I got slight power to both wires. When I switched up the PAMCO wiring, the bike fired up on the right side only (meaning that both points are firing when hooked to a working coil).
So, a new coil will be coming soon. Hopefully it is returnable, because both coils came together, brand new.

I could not get the right side to run when I switched the plugs (no spark from that left coil), and the left cylinder (working coil from the right side) was backfiring every now and then, but didn't run. Could it be flooded with fuel at this point? How could I fix that? I want to make sure that the left cylinder is ready to roll when the new coil gets here.
Thanks guys for the pointers, and please steer me the right way if I am drawing inaccurate conclusions.
Thanks for the help so far!
 

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Sorry for the slow reply - currently out of the country. How did the new coil work out? There's a test procedure for coils on here too if you dig a bit, it's probably Sprint66's - I'd guess at it but then you'd really end up needing a new coil :D
 
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