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Electric Gremlin in Start System 93 CB250 [SOLVED]

Gritty22

Member
Joined
Jul 17, 2020
Total Posts
14
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0
Location
wyndmoor, PA, USA
Hey Twins Fans,

I have a mystery with my '93 CB250, and before I start tearing things apart I thought I would see if anyone here has seen this before.

On a few occasions now when I have been out on the bike and after making a stop (either for a while or short time) when I have jumped back on and hit the start button I get nothing - not a missed start, not clicking, not half hearted turn over: nothing. All lights (headlamp and dash go off) and the bike is dead.

First time of course I assumed a fuse or something, but the strange thing that occurs is when I get the bike started (thank god for light bikes and gentle slopes right?) after a bit of twinkling on the dash lights the thing is totally back to normal AND the next time I get on the bike I hit the button and go like every other time.

This has happened three times now (to the point that I never stop the bike at the bottom of hill any more) and it is so odd.

My only thoughts are a loose ground or a slowly dying solenoid - but you would think such things would either work or not work right?

So, before I tear apart my electrical system and start replacing things at random - Anyone had an experience like this before?
 
Don't do the random replacement game, waste of money and time. I would start with the battery and get it tested, if it passes then good. Clean the battery cable ends before re-installing and be sure they are tight. Might pull the other end of the ground cable and clean it and be sure it's tight as well.
What work has been done in the last 3 months?
After the battery get a good test light and take a ride when you have time to be parked for awhile. When/if it quits it'll be time to actually perform some diagnostics. Starting at the battery follow the Red wires checking for voltage, if that's all good then proceed to the Black wire coming from the ignition switch, That is the main electrical feed to everything else of importance. You'll want to have a copy or access to a copy of the wiring diagram with you and a few hand tools need to take some things apart for checking.
 
Take a piece of electrical wire along and, next time it craps out, lift up the seat and jump between the battery post and one of the black wires(the connection on the turn signal flasher or the rear brake light switch would do nicely). If things light up with the jumper wire, check out the key switch and/or the wiring to it.
 
Reply to LongDistanceRider:


The only things I have done are replace the levers after my neighbor backed into the bike and knocked over (that was fun...). But on this bike that is a bolt and a cable, shouldn't be able to cause this issue.

Your check list looks solid, that's more tools than I typically roll around with, but it's worth a shot. I am totally stumped obviously so diagnosis is the best approach for now.
 
Last edited:
Take a piece of electrical wire along and, next time it craps out, lift up the seat and jump between the battery post and one of the black wires(the connection on the turn signal flasher or the rear brake light switch would do nicely). If things light up with the jumper wire, check out the key switch and/or the wiring to it.

Thank you - I will try this. Sounds like you suspect a loose connection at the ignition switch, which I had not considered.
 
Loose connection to the switch, or the switch itself (internal defect). You could rinse the switch with contact cleaner and dry it with air pressure. I would start there, because it seems that the whole power supply is the coolprit. A bad contact in the fuse box (main fuse) could also play a roll.
 
Sounds like a bad/intermittant connection and the above advice should serve you well. As for why it comes and goes, a a bad connection can create resistance in the affected circuit, resistance creates heat which increases resistance more until the connection fails altogether. After sitting a bit the resistance goes back down and it works again.
 
I can't help but wonder if the ignition switch was damaged when your neighbor knocked the bike over?

There's a thread around here somewhere about wiring a toggle switch in place of the ignition switch, it might be a good diagnostic tool.
 
Sounds like a bad/intermittant connection and the above advice should serve you well. As for why it comes and goes, a a bad connection can create resistance in the affected circuit, resistance creates heat which increases resistance more until the connection fails altogether. After sitting a bit the resistance goes back down and it works again.

Thank you for sharing this. This is exactly what is happening if I don't bump start it and wait 20 minutes to a half hour the circuit "fixes" it's self - which is why I was so confused. Makes more sense now.

I haven't done anything yet, but it looks like the temps will finally dip bellow 100 million degrees this weekend, so I'll finally get a look inside.

Thanks to all for your helpful replies - I'll update once I open it up and get a look inside.
 
I can't help but wonder if the ignition switch was damaged when your neighbor knocked the bike over?

There's a thread around here somewhere about wiring a toggle switch in place of the ignition switch, it might be a good diagnostic tool.

Thanks - I wouldn't rule it out. He actually knocked the bike over in the dark and instead of just coming to tell me he decided to try to put it back up and managed to dump it on the other side in the process (so it actually went down twice). Who knows what internal damage might have come to pass, though it was a couple months ago at this point.
 
UPDATE: Solved

Hi guys. Thanks for all the tips and advice.

I managed to fix the issue, and it was much easier than expected, though I brought it on my self.

No one got it exactly correct, but that’s because I left out a detail that I did not think was relevant.

Back when I first got the bike (before it’s first winter storage) I bought an oximiser battery tender for it. It came with a small wire harness that could be wire to the battery and tucked away when not in use.

Well, it seems over time that the coating on those wires deteriorated, so the wire to the positive terminal when touching the frame was now grounding, and that was stealing all the juice.

When it wasn’t in contact everything was good, then wiggle the bike a bit (or ride it obviously) and it was dead.

I simply pulled it, I’ll use the clamp connector next winter.

Thanks again for the input - see you in the twisties.
 
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