Columbia Commuter possible weak spark.

Greetings. First post.

I have a Columbia Commuter, mfg Dec. 1976, which I've had since the early 90s. It says 505/1 near where the wires exit the stator area. It has about 330 miles. My nieces or I would ride it occasionally until the late 90s. By then, the inside of the tank had gotten rusty and would clog up the carb regularly. Otherwise, it always ran fine. So, one day we just left it in the corner of the shop. It set there for the next 20 or so years until 3 weeks ago when one of my daughters asked me to fix it for her.

I got it out looked it over and ordered a few parts.

Today, I cleaned the carb and its jet (Bing 85/12/101 carb - more about this later but it's a less pressing question - leaking - assume float level). All carb passages are open.

I put a little ebay 1 liter plastic mini bike tank and a new air filter on it to see if it would run. It did not. I replaced the plug with a new champion L82C, which is the same make and model plug which was in it already. I set the points to .016. It still did not run. I replaced the plug wire but no change. I can take the plug out and ground it so that my hand touches the electrode and ground my hand to the engine. I can take the shock slowly turning it over but if I turn it over faster, it hurts. I cannot see the plug arc by grounding it to the motor - I'll try to see it again after dark.

The flywheel says 6V 22-5/10W. What appears to be the condensor behind the flywheel has wires soldered to the end of it. The stator has a total of 5 wires exiting it, 3 from one grommet and 2 from another.

I cannot get it to run at all, even on ether.

I would appreciate any suggestions.


Re: Columbia Commuter possible weak spark.

dont use ether please, use premix in a bottle, a couple squirts should do.

check plug gap, and of clean grounds to the body, including the coil mount.

Re: Columbia Commuter possible weak spark.

Thanks for the response.

I set the plug gap at .020 per the manual. Also, when I took the stator cover off I had removed the coil so I could get the cover off. Prior to reinstalling the coil, I cleaned the bolts and where it bolts on with a wire brush on a dremel. I also disassembled/cleaned the on/off switch and treated it with dielectric grease.

Since its dark, I went back into the garage and turned the lights off and there is not enough spark to jump the gap. There is spark as you can feel it as I described in my first post.

I will try and clean more wires/connections tomorrow but they don't look bad.

I do have a multi meter but I don't really know how to test the coil.

Will a bad condensor cause weak spark as I'm describing?


Re: Columbia Commuter possible weak spark.

did u clean the points? the external high tension coil grounds thru mountung bolts as well clean those, also theres a wire frame ground too. make sure your plug cap is screwed in on some fresh wire.

it will fire with a bad condenser but will have a miss, or uneven power, cut out when hot, or misfire but should run. (edited)

Re: Columbia Commuter possible weak spark.

When you're chasing ignition woes a cheap spark checker is helpful. I bought one at Harbor Freight Tools, though if you can contrive to attach a heavy battery clip (alligator clip) to any old spark plug with its outer electrode snapped off, that'll work too.

Note that you may have a bad spark plug wire, or one with corroded screw-in terminals at either or both ends. That, and dirt that's short-circuiting the coil wiring can cause all sorts of merriment. For the latter, apply WD-40 or other hideous stuff like PB-Blaster. (Watch it with PB, though: it'll dissolve all sorts of interesting stuff like styrene plastic.)

With any old machine, the standing orders are simple, albeit miserable, for each and every system: (1) after taking numerous digital photographs of the system to be serviced (it's very easy to forget how it went together) disassemble without losing parts or breaking anything (2) clean every part thoroughly: wire-brush off the old rust, paint stuff if necessary

(3) polish to a glorious shine anything that even vaguely looks like it might be an electrical connection. Apply a bit of grease to prevent future corrosion therein. (4) replace anything made out of rubber if you possibly can. Silicone gasket former is good stuff for this. (5) And then re-assemble with anti-seize compound. Assume that you'll have to take the fool thing apart again, too.

Mark Kinsler

Re: Columbia Commuter possible weak spark.

I will try those things to the extent I havent already don them as mentioned above. I'll also go ahead and order a new condenser, etc.

Re: Columbia Commuter possible weak spark.

A question before I get back to work on this moped this weekend: I’ve read a few posts about various mopeds with a “hidden resistor” or something along those lines in the tail/brake lights circuit(s), where a problem in this circuit would prevent proper sparking - does the Columbia commuter suffer from this sort of design as well?

If so, what do I do to bypass the issue to test for it?

I’m attaching the wiring diagram below.

The horn works and the taillight works, as does the headlight. My wife could not see the brake light illuminate when I would pull the brake lever. But I might not have been able to spin up enough rpm while pulling the brake lever so that my wife could see the glow. The taillight was very dim she said.

Thanks (edited)


Re: Columbia Commuter possible weak spark.

Someone may have to lend a hand here, for I've forgotten some details and may not have things quite right, but: to avoid using more than one lighting coil in the magneto (heaven knows why) the learned scholars at Bosch decided to use the ignition coil to run the tail light. (Also the horn in some cases.)

So what they did was to install six magnets instead of one on the flywheel. The ignition coil used have one end connected to the ignition points (that's still the case) while the other end was connected to the frame of the bike.

Now, this "frame" wire from the lighting coil goes back to the rear fender and is connected to one terminal of the tail light bulb. The other terminal of the tail light bulb is connected to the frame of the bike.

This ensures that the tail light will always be on while the bike is running (note that the ignition points are closed for all but a brief portion of each rotation, so while the points do open and close, they don't interfere much with the current to the tail light.)

Problem: if the tail light's delicate tungsten filament burns out the current through the ignition coil will cease, and you'll be stuck out on some country road with the narrowed eyes and shotgun of some moonshiner leveled at you, you hippie.

And so there's a big ten-watt resistor, far less likely to burn out, connected across the tail light terminals. This will carry sufficient current to run the ignition even if the tail light bulb has burned out.

Insofar as I know, the resistor lasts forever, but I don't like the whole arrangement. As for the horn, it's possible to use the ignition coil to run that, too, but it works better if a silicon diode (just a one-way electrical valve) is installed in series with the horn terminals.

I am planning the following improvements on my Trac Clipper (just a two-coil Bosch) ignition/lighting system. The idea is to use 12 volt LED lamps, ten of which I got from eBay for a modest sum.

These require 12 volts DC. The Bosch lighting coil provides around 6 volts AC, more or less. (Unlike the electrical outlets in your home, the actual voltage varies quite widely when you vary the number of lamps being driven.)

The solution would seem to be an old-time circuit called a 'half-wave voltage doubler,' which requires two fairly heavy-duty silicon diodes and two big capacitors whose size I'm guessing at.

The lighting coil would drive this circuit, which isn't particularly large and could be tucked anywhere on the bike. An LED headlight, license/tail light, brake light, and speedometer light would be connected in parallel across the voltage doubler output. (It is hoped that the LEDs' small current requirements will permit this.)

A shrill, non-stock DC horn could also be driven from the doubler.

I've bought all the parts (they were cheap) from eBay, but since I have no specifications for the Bosch lighting coil (I need its voltage and AC resistance) or the current requirements for the LED lamps I bought, I'll have to just build everything and see if the bike will light the lights.

Mark Kinsler

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