Topic: CB125S ignition problem

[natez]

Hey guys,

I've done some searching on this forum and gotten a couple clues from other peoples issues, but mine seems to be just alittle different.

I have a CB125S motor that I bought 4 years ago and have ridden here and there. Its never been thrashed since new (i knew the original owner) but since I have gotten it, I have not done any maintenance to the motor other than cleaned the carb every time it got clogged from sitting for a while.

Bike was running all weekend awesomely, brought it home to drop somthing off and got back on to go to a buddy's place, pulled out onto the street, went through three gears and it just died. Just like that, no popping, sputtering or anything. Just quit. Couldn't even get a pop trying to restart it. Walked it home, pulled the plug and no spark.

What I've done so far:
-Tried two different plugs
-Made sure all wires were ok, checked grounds, ect.
-checked the spark plug cap, couldn't get any resistance reading, so put a new one on (also cut a bit off the end of the spark plug wire to get a fresh install on the new cap)

After I did that, I got spark back, and got it running, idle's great, but anything past 1/4 throttle is now followed by a severe miss (not a bog, more like when you hold a car motor at the rev limiter) Both original and new plug got the same result.

Im waiting for some penetrating fluid to loosen my ignition cover bolts so I can check the points. Then it will be the condenser, coil, then I dont know. Before I do all of this, does this sound like anything in particular to anybody? The engine is somewhat running like it would if there was no battery installed, however with no battery the engine will quit with the application of power in gear, the way it is now it will keep running with power added albeit like crap.

Also I dont think its a carb issue seeing how its such a sharp miss and not any sort of bog unless i really wap the throttle hard.

Any advice appreciated.

Thanks,
Nate

[grcamna2]

your points may have closed up.

[natez]

Just checked, points look good. Guess its time to order up a new coil and condenser?

[grcamna2]

Nate,
   If it was me I would first check all the electrical connections and make sure they are making good metal to metal contact and especially the grounds...and then test the components in question by the book.Do you have a Good Service manual ? If so it will have all the procedures for you to do the proper tests and then determine which parts are defective;a standard multi meter should be what you'll need. I love those little CB125S's ,they are great all-around transportation and most of the time will run forever when properly maintained.

[natez]

No spark now.

Also, the bolts on the condenser/coil were alittle loose, but not much, enough to be able to move the condenser tho. I tightenen them up. Still no spark. I have a new condenser on order already, any way to test the coil before I order one?

Also, the plate that holds the points, i know there is an adjustment for this, is it really possible for this to move once its set? (The screws are tight) Could this be the problem?

-grcamna2: no, i don't have a book, i really need to get one but have been putting it off since it has not really been giving me any trouble. Guess its time to do it. Is there any source online for a free download? (All electrical connections seem good)

Nate

[grcamna2]

Nate,
           I would start repair w/ a decent used Service manual(book) off of Ebay and follow all it's recommendations from there; you'll get it done best that way.

[old76cr]

Hi. Try   http://www.mediafire.com/?lay10zmzxqn    for a shop manual. I used this for my sl125. Check your ignition advance under the points plate as I recall? Maybe a broken spring?

[grcamna2]

You may want to check your kill switch and all the black/white wiring coming to it and going away from it through the ignition circuit,those kill switches on the right handlebar switch can lose continuity sometimes .