Another question for the 125 experts on here. My RS125 is eating up ignition coils. I'll get about a day or less out of them, then the primary side goes out of spec. Then the bike starts running like crap all over the RPM range. If it goes far enough out of spec the bike doesn't run at all. I have gone through 3 coils in two and half track days. The problem seems to be getting progressively worse. The last one went enough out of spec to where the bike didn't run and only had a half day on it. Secondary winding checks out. I did all the electrical checks in the manual and everything tests within specs per the manual, except the primary winding of the coil. I did check this last coil before putting it on, and it tested out within specs. The only thing I didn't see have a check was the regulator/rectifier unit and was thinking of replacing this along with a new coil. But before I drop money on guess parts, thought I would check on here to see if anyone has had similar issues. Or might have an idea on testing the reg/rec unit. For reference the bike is a 98 Honda RS125. The primary is to be at .45-.55 ohms. Bike runs crappy at .8 ohms, doesn't run at all at 1.8 ohms. Thought this may help. Any thoughts or ideas on what may be causing this?
Is the battery holding a charge? I got nothing.... And I don't have any of those spares to let you swap and try either... sorry.
Thanks anyway. I was struggling with this one myself. Think I found the issue with this particular coil. It seems the body of the coil broke loose from the iron core that goes through it. It is jiggling around a little. If I take the primary reading and tap on it, the impedance fluctuates. Not sure why the other two coils went. Unfortunately I already tossed them, so can't do further investigation. Maybe I was just really unlucky on those coils. They were all the spares that came with the bike. So will throw a new one on and hope it was just bad luck. But if the forth one goes quick I'll be pissed at myself.
Have the coils been securely mounted? I am wondering if the coil has been vibrating due to a loose mount, which might cause the damage your seeing in the coils. Just a guess...
I wish I could say for certain if they were or not. I know the last one was securely mounted. It had less than a day on it from when I mounted it. But it was a used spare, so maybe it already had the issue and was lucky to get the half day or so out of it. I'll definitely make sure the next one is mounted right. And be watching it like a hawk.
Coil location is on the side rail(somebody moved it for airbox) or front center of main frame?Maybe a loose weld or bad ground? .... Or the spare coils that came with the bike were just spare junk?
Yes the coil was moved for an air box. The mounts don't seem to have any issue, not that can be visually seen. I did check the ground connection for continuity. The bike also has an additional ground connection to the frame at the stay. I checked all connectors to see if there may be any issues there. Everything seems to point to only the coil being the issue. Just going through 3 of them, I was thinking there may be some other issue driving the failures. At this point I'm thinking all the spares were junk.
You might want to take a file to the two coil mounts and make sure they both have the same flat mounting surface. If the mounts were welded on there and not filed perfectly flat (on the same plane), the torque could be twisting the coil causing your failures. It's also a good way to ensure your ground surface is nice and clean without any oxidization. The spark plug boot is a wear item as well. 1-2 seasons on them and they should be replaced. You can trim the high tension lead 5mm and reinstall the plug boot as a clean up item every so often but obviously this is a limited thing to do. Cleaning inside the cap is a good idea as well. Also, spare coils generally become "spares" when they should be just thrown away. I've never heard of anyone replacing a coil as a wear item or as a general precaution. Thus any used coils are probably just junk. Just my .02 worth Peter
You are also facing the possibility of causing severe internal damage to your CDI. TCI ignitions generally don't care if the coil is disconnected - hell, they sometimes can't tell! The cap and firing SCR on a CDI, however, have a very specific path that wants to be discharged through, and removing the coil from that path can really screw things up FAST. So far, whatever has been happening has been increasing the resistance but still maintaining continuity to ground. If that coil connection suddenly fails, you might lose your black box in very short order. Good luck.
Thanks for the input. Checked the mounting points and they are level and straight with each other. So far all the coils that came with and on the bike are in the trash now. Going to order a new one and hopefully all will be good to go from that point. Just hoping nothing else has gotten damaged from the bad coils.
