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Preface: Been troubleshooting this the last few days on a bike I brought back to life out of someone's building after about two years of sitting. Replaced top end because it dropped a valve before it was parked, then replaced fuel pump, fuel filter, air filter and plugs because the pump was bad and had old gas from the time it was parked. Didn't properly clean out the tank but I dumped the old gas and have ran about 15 gallons through it by this point with fuel treatment. First time out on the bike I ran it slap out of gas primarily due to stupidity, but had no problems filling it up and riding off again.

Now to the current issue: Going down an interstate with my brother after about 80 miles of riding that day before the bike bogged down around 65mph @ 5.5-6k rpm. Got my brother's attention and we pulled over; when I pulled the clutch, the bike slowly gave up. Started it again and it sounded like it was running on 2-3 cylinders, so at this point I figured the top end was gone again and just hauled it back home. Took about 90 minutes to get home and once it was in the building I tried starting it up to get a better idea of what happened. Bike fired right up like nothing was wrong and took it down the road about 2 miles with no problems before parking for the night. Woke up the next morning, took it to the store about a mile down the road and the issue was present again. Parked the bike for 4-5 minutes while I picked up some stuff, came out and the bike fired up and ran long enough to get me home before showing the same symptoms. In these gaps, the bike runs like normal; no bucking, no sputtering, no loss of power, no abnormal noise.

I've pulled the stick coils and the plugs to inspect and test primary and secondary resistance on the coils and they're all within spec: 1.6 ohms across the board for primary and between 9.65 to 9.95 kohms for secondary. The plug from the #3 cylinder seemed to be wet with fuel with a noticeable fuel smell while 1, 2, and 4 didn't show this. The firing ends are grey with a black ring around the threads, even the plug with fuel on it despite being wet. I also checked for a vacuum in the fuel tank by popping the lid open the second time this happened (the trip to the store) and the problem persisted. About 200 miles before this issue occurred I did a mixture adjustment to solve a bad hunting idle and delayed return to idle. The bike ran well after this adjustment, no hunting idle and significantly better return to idle.

At this point I'm thinking it's a bad coil for #3 cylinder, but when the coil is cool it tests perfectly within spec and I just don't have the money to replace parts that don't need replacing. I also have no idea how to isolate this coil in a running scenario to unplug it while it's acting up for an rpm drop test because first, I've gotta ride it enough for the problem to occur, then I've gotta take off the tank and airbox before unplugging the coil. Just doesn't seem feasible to me. Also can't really ride it to a shop for a peak voltage test because the nearest shop with this capability is some 30 miles away.

Any insight would be greatly appreciated, and thanks for reading my desperate wall of text. Also, I'm not a mechanic, just a dude with some tools and a Haynes manual.
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