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I bought a 1982 CB650 a week an half ago as the guy selling it couldn't get it running and he didnt know anything about engines. He also didnt want to even try with it.
Said he had a new battery, but it must have froze over last winter in MN and it was bad.
Replaced the battery.
The guy also said that he had someone rebuild the carbs last spring, but he believes that it was a kid that didnt know what he was doing and was right out of school. It was back-firing badly and that he could get it to run but it wouldnt stay running.
So as the battery was charging I pulled the carb rack and cleaned it...after dealing with some stripped screws.
I dont think that other guy touched it, it was pretty gummed up.
Let the needles and jets soak in some carb cleaner overnight, put it back together and after reading a little bit on some of the carb issue, I made sure that things were tight to prevent any vacuum leaks.

So...I got it running, but there was the backfire! Sounded like a gunshot.
(See link for video) youtu.be/oR-_nz2rtl0
My first thought was to test the coil/spark as there must be an issue with coil not sparking regularly or the firing order was off.
Pulled the Coils off, did some scrubbing on forums. Most were saying coils should be 3 ohms primary.
I thought they were bad as mine were only 2.5 ohms primary...and I couldnt get anything (open) secondary from the + to either of the secondary.
Did some more searching how to test the secondary, and with these coils, for this bike, the AW82-Tri Coils, secondary is between both the outputs an should read about 12k ohms across them. +5k for the plug boots.

AW82-Tri coil is 2.5 ohms primary, 12k secondary +5 boots.
I then learned that the plugs, at least one, had to be connected to ground/installed for them to even be tested properly.

I also learned, firing order really doesn't matter as long as the correct coil corresponds to the correct cylinders. Coil (blue wire) on the left (port) of the bike is for cylinders 1 & 4. Coil (yellow wire) on the right (starboard) is cylinders 2 & 3.
The coil fires both spark plugs at the same time, one cylinder is 180º from the other on the same coil. One will fire on the compression, the other on the exhaust. I understood that it was also an emission thing, to help burn up any remaining gasoline.
Back to trying to run it. When I had the plugs out and replacing them, they were all black and sooty. So, running really rich.
Somewhere along the line I had an epiphany...Running rich....exhaust stroke w/ spark....backfiring.
BAM!
I decided to back down the mixture screw on 1 cylinder (#2 was the only exhaust that was cold yet) to only 1 turn out...no drastic backfire anymore.
I backed the others off to only 2 turns out. Still chugs a little right now and had to back down the main Idle screw.
Right now, I am going to pull the carbs back out and clean them and probably do a rebuild kit for them. Go through the bench sync and read up on tuning.

Hopefully someone can learn from my trials and wracking my brain the last week.
Not in the clear yet, but here it was, running tonight.
youtu.be/CaBomtvFR9A
 
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As we all well know in Minnesota you have to store the battery in a warm place in the winter. Other then that, I can't help you much. I do what I do and others do what they do.

However, after reading your post you seem to have it.

Welcome from Minnesota! :thumbsup:
 

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Thanks for the welcome!
Pulled the carbs this afternoon and just going back through them. I found the idle screw for #2 broken and the tip stuck up in the main body. Any ideas for removal without marring up the aluminum?
 

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Victory is sweet.
Bike is up and running well! (Or at least it seems that way to me)
I was able to drill enough of the tip with the smallest drill bit I could find and then pop it down the canal.
Bike shop in town had a bunch of 650 parts in a box that he was able to give me a screw for replacement, score!
Now I am able to go for a joy ride...on probably the last warm and nice day left of the year. Just in time!
 
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