Topic: cb125s started and ran this morning, now no spark

[1974blaze]

i've checked fuse. all lights work. 6v into the coil. points gapped properly. just no spark.

how do i check to see if there is voltage running to the spark when it kicks? also, i've swaped plugs 4 times (none of them brand new) and no difference.

help please.  sad.

[kirkn]

The 6 volts measured at the coil must then go THRU the coil and thru the closed points to ground.  That's the circuit.  So -

How about 6 volts at the points when they're open?  Dropping to zero volts when they're closed.  Clip one voltmeter lead to the spring thingy bit of the one point and clip the other lead to good ground.  That will confirm that the points are actually making and breaking electrical contact with each other (even though by a visual gap-check, they appear to be closing).

Otherwise, if ya still got no spark, I'm thinking bad plug (unless you can walk that suspect plug right over to a different machine (bike, car, mower) and watch it spark well there.

Finally, my opinion on the Honda 6-volt systems is that they REALLY like 6.5+ volts to spark.  My own '72 CL100 can barely (or not at all) spark with normal 6 volts from the battery, but hook a battery charger up to it to give it a bit of a helping hand, and it'll spark great and start right up.

Good luck with it!

Kirk

[1974blaze]

thanks kirk that's all really good advice.  here's where i'm at...

good voltage everywhere.  went and bought a new plug, asked if they had a new plug wire cap for me on a hunch, no luck there of course.  came home and put in the new plug and re-attached the plug cap.  three kicks, fired-up.  hummed purfectly and i thought, i should ride a mile and see how its going.  half way down the driveway, she quit, no sputter, just dead.  clearly electrical. 

i have a suspician that it's the connection from the coil to the spark plug.  can you just trim the wire a little and re-screw in the plug cap? would that help?

any other thoughts.  on your advice i have it on the charger.  battery was totally dead after leaving the key in the "on" while i walked the dog since the tail-light stays lit. 

[kirkn]

i have a suspician that it's the connection from the coil to the spark plug.  can you just trim the wire a little and re-screw in the plug cap? would that help?

any other thoughts.  on your advice i have it on the charger.  battery was totally dead after leaving the key in the "on" while i walked the dog since the tail-light stays lit. 

Yes, you can trim the plug wire back (about 1/4" or so) and rethread the cap back on.  In fact, I've done it to my own CL, and a KZ400 I used to own.

Fully charged battery is a must, as you can imagine.  Without it, you're never really sure what you're dealing with, in terms of electrical problems.

Other thoughts - how 'bout an intermittent kill switch failure?  Loose wire at the kill switch or ignition key?  A sudden total loss of electric power sounds a lot like a loose wire or bad switch...

[1974blaze]

agreed, and i installed new superbike bars which came undrilled, which means i had to drill holes and re-run wires some of which i had to cut and reconnect with heat-shrink butt splices. 

that sounds suspicious now that i write it down...

i'll pull the kill switch and check the wires.

[1974blaze]

ahhh!

well, trimmed the plug wire. got new plugs.  ran great.  checked the wires from kill switch through bars, all good. 

today fired with 2 kicks.  ran like a champ at idle. after it was warm i did a point gap check and went into the ignition timing adjustment.  i set it statically and then checked it with a strobe.  strobe showed it way off, over advanced.  so, i started making adjustments with the motor running.  the only way to get the  f mark to come anywhere near the notch was to super-retard the timing??? and, when i did this the idle raised and smoothed.  weird right? think is, it won't START when it's set this way.  so i move it back to original advance and start over.  same result.  wtf.

and of course, to make me really mad, it won't start at all now and i get spark only sometimes when i lay the plug against the case. 

i'm going nuts with this bike.  any change the coil is going and causing all of this?

[Flying J]

2 questions, did you sort out the problem?
and how do you time the motor while its running? I have a CL125s. It has the same motor and when i open the stator cover there is oil.

[bryanj]

DO NOT use a strobe for timing to the "F" mark that is for static only

Use a strobe for checking the fully advance marks when reving

[1974blaze]

yes, it's running like a champ.  turns out it needed a new stator, and other ignition things probably, so now it has an ignition system from a xl125 which doesn't require a battery to run.  now the batt just supports lights and horn.  expensive fix, but hey, old bikes....

when you open the cover, there certainly is oil, so it's a messy job.  i propped it up fairly vertical to minimize the spill-out while doing the timing and put a pan under it.  still, some oil kicked around the garage, but nothing too bad.  once it's vertical (put a block under the side stand) the oil stays pretty much in the bike.

[1974blaze]

yeah, +1 on the above comment.  i learned a lot on this bike.