Vintage Dirt Bike Q & A

I have a 74 Honda CR 125M I just bought from a good friend. About 6 weeks ago he rode it across his yard to put it in a different garage and turned the fuel off, let it run out and quit and put it inside. We made a deal and I bought the bike and went to pick it up a few days ago. Got it home and decided to fire it up yesterday, now the bike has no spark. I tried un-plugging the kill switch (aftermarket) and made no difference. What do you guys think could have happened to it just sitting? CDI, coil? Any help is appreciated.

I never had any issues with a 125 ignition. I suspect the spark plug is the problem, replace with a new one and just try to start it, dont try to visually "see" the spark.

If no love, next would be the plug cap to inspect.
Aside from that I used to isolate the plug wire from the frame wrapping it with an old tube so there would be no change of grounding to the frame.

Good luck

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1994 AHRMA National Champion Sportsman 125 Intermediate.
1996 AHRMA National Champion Classic 125 Expert.

I forgot to mention I already tried a new plug. Still nothing. Is there any way to test the CDI?

IF it ran fine a while ago then things should be ok, aside from grounding issues. Grounding in anything is the biggest problem.
Check for mouse chewing on wires, check the connections esp the one just above the countershaft, pull it apart inspect then re connect all.
Also dont need an "R" plug as the cap has a resistor (OEM)
No, cant test the CDI.
Make sure the coil is in good contact with the frame as a ground. Remove and sand the contact areas and replace.
Check that the kill switch wire is not gronding.
Check the plug cap (OEM cap), inside is a noise supressor if you unscrew the inners of the plug cap there is a carbon looking shard in there that sometimes goes bad.
I would unscrew the cap from the hi tension lead, clip off 1/4 in from the high tension lead and re screw the cap back on OR replace te cap wit another known good one.
Resistor caps should OHM @ approx 5k. non resistor at minimal.
Ignition coil green wire & plug cap 10,600 ohms (10.6k ohms)
I would pull the ignition cover for inspection, check the rotor for rust and if things in there look crusty you may want to remove the stator and check the stator plate to case for corrosion, clean it up and give her a whirl.

I would suspect the coil going first as the CDI's were pretty good.

Good luck


Husqvarna's had issues with the mag engine cases vs aluminum stator plates losing ground from corrosion, the Elsies never had that issue.
Motoplats had issues with the internal resistor going once the engine got hot, Elsies dont.

C'omon Honda don't fail us....

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1994 AHRMA National Champion Sportsman 125 Intermediate.
1996 AHRMA National Champion Classic 125 Expert.

Thanks for all the tips. I will check everything over this weekend. Just seems odd that it was running great, and then nothing. That's why I was thinking CDI. Thanks again.

id be checkin out the jets in the carb. perhaps a snerd of goo in the float bowl plugged up a jet when you let it run out of gas. just a guess. good luck. interested to know what the problem turns out to be.

Picked up a different CDI and coil from a great guy on the Vintage MX swapmeet. Swapped out the CDI first and we have ignition! Runs great! Thanks for all the help guys, it is appreciated.

SWEET,
thats a first for me seeing the CDI give up the ghost.

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1994 AHRMA National Champion Sportsman 125 Intermediate.
1996 AHRMA National Champion Classic 125 Expert.