1 Low power/possible coil problem--help needed **SOLVED** Wed Mar 30, 2016 1:52 am
KJustin
Silver member
I started it up and it seemed to be running fine. As I was backing up out of the garage I turned the bars to lock and the engine died. Restarted and everything was fine, but thinking that maybe I had a short somewhere I moved the bars about and jiggled the wires running from the bars to under the tank. I reproduced the issue by moving the bars to lock. I recently added an alternator exciter light (I have installed an Acewell speedo). I wasn't having problems with charging, but I saw a thread on the forum about the lack of an exciter light resulting in a an alternator charging failure and I thought I might add one just to be safe. So, I figured that maybe what I did with the exciter light was causing a short somewhere. Or maybe the light was't appropriate. I used an LED that was 1/4 watt with a 680 ohm resistor built in to it (purchased from radio shack for something else...had it lying around and doing the math, I thought it would emulate the 3W incandescent... but maybe I was wrong on that). So, I pulled the tank, unplugged the exciter light, reinstalled the tank and starter her up. Everything was running fine and I did not have the problem with the engine dying no matter where I turned the bars. Problem solved, I thought. I rode off a few miles on an errand and parked the bike.
A few hours later I started up the bike, no issues. Rode about a half mile and all of the sudden had a massive lack of power, followed by many back fires. The bike died. I restarted it, just barely, and was able to ride a little with lots of backfiring and lurching. Very little power, and to get even a little power, I had to keep the throttle at least half way open.
It sounded like one of the cylinders wasn't firing. On a lark I wiggled the injector wires and cylinder 2 wire came off in my hand. Upon close inspection I saw that I had installed the retainer clip backwards (I had the injectors out months ago chasing down another problem, which I solved) and therefore it wasn't securely attached to the injector. I reinstalled it properly, the bike started and I was able to limp home, but the bike was still not running well. It would barely idle and I had to keep a bit of throttle on to prevent a stall when idling. It seemed as though I wasn't firing on all cylinders.
So I pulled the plugs to see how they looked. Cylinders 2 and 3 were perfect. Nice grey tips on the plugs and looking into the cylinders, they were dry. Cylinders 1 and 4 were slightly fouled, smelled slightly of gas when I pulled them, and looked a little wet inside the cylinders.
I dawned on me that the commonality is that 1-4 runs on one coil and 2-3 runs on the other coil. So, I thought maybe I had a bad coil. Looking at Crazy Frog's trouble shooting guide, I tested the coil resistance. On the 1-4 coil the primary was 1.0 to 1.2 ohms; Crazy Frog's guide says it should be 2.6 ohms. The 2-3 coil tested at 2.6 ohms on the primary. I couldn't get a reading off the high voltage terminals on either coil. I must not have been probing them properly. I removed the plug wires at the coil terminals and put my probes in to contact the metal inside...not sure what I was doing wrong. (I understand from Crazy Frog's guide that they should be 12.6 ohms). If anyone can tell me how to properly probe/measure the high voltage portion of the coil, I'd appreciate it, as I think it would be helpful in confirming (or refuting) my diagnosis.
Based on the low reading on the primary, I'm thinking that I've got a bad 1-4 coil and that I need to replace it. Based on the above, does anyone agree/disagree?
However (and this is the reason for the long post) are any of the other things that I described above related to the coil (apparently) going bad? Is there any chance that my exciter light did something to the electrical system causing the coil to fail? Is there any chance the #2 injector coming unplugged somehow lead to the 1-4 coil failure? Or maybe I just had a bizarre confluence of the coil failing unrelated to anything else?
Last edited by KJustin on Sat Apr 16, 2016 2:09 am; edited 1 time in total
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1985 K100 Cafe Racer (formerly an RT), VIN 0051736