HONDA CG125E RUNNING ERRATICALLY

[UKKWF]

Happy new year everyone.... ive only really posted on here because i havent got work or college for a few days, i work in a motorcycle garage and im studying motorcycle mechanics level 2 at college.So will obviously take my problems there when im back, just wondered if anyone could shed some light on here too..

below is video of my cg running atm. just had to rebuild the top end, but that's irrelevant. Bike is running erratically, and given any throttle at all it just dies... I believe its the points, they look slightly burnt/pitted in the middle and i had tried wet n dry but to no avail.. set the gap at 0.35mm and the ignition timing. Just to be sure the points are meant to be set with 0.35mm clearance and start to open at the timing mark F... correct??

i have ordered a new set of points anyway because i believe thats why its running bad... I believe the condenser is ok because i bought that new with the ignition coil. Spark seems ok, it is blue, and isnt the plugs as ive swapped and tried with new ones all seems the same. Believe someone said it could be the woodruff key on the flywheel if its worn?? anyone know anything about this... also the mechanical adv/retard system in the flywheel seems a little loose but not too bad.

valve clearences are set ok, battery is fully charged and working fine, airfilter is off because it was a crap chinese pod one, but ran the same with it on - i dont believe its anything to do with jetting, gaskets are all ok and no airleak from carb to inlet manifold...

Anyway cheers...


video......https://youtu.be/JnQlIViiF_8

[UKKWF]

also when setting the ignition timing, i was using a continuity tester with the lead attached to the batterys pos + and attaching the screwdriver end to the black wire running off the flywheel...

the light is suppose to go off/dim if the points are set correctly when the flywheel is aligned with the daytum mark on the bike and the F on the flywheel right? because no matter what i did the light never went any dimmer or went out. Could the ignition timing still be wrong???

[misscrabstick]

what should happen is that when the points are open there will be no earth and the test lamp will go out, doing it this way though you don't want that black wire connected to the charging coils or the ignition coil or you will pick up false grounds through them making your method null and void.

Double check your cam timing if you have a chain on it, strip and check the carbs clear of debris, the ignition timing would need to be very retarded to stop it revving.

Wet and dry is useless for refacing points, you need a proper points file, but if they less than perfect best fit new ones, if you are seeing a lot of sparks across the points gap suspect the condenser.

Ht lead ok? lead ok? not shorting/arcing out?

[UKKWF]

[misscrabstick]

What does the honda manual say is the best way? might be dynamically using a strobe, the issue I think your going to have is the ignition charging coil being attached to the points, it's going to provide a ground that's going to mess up a test lamp I reckon. How about a multimeter on ohms? connected to ground one side and the black points wire on the other, as the points open you will see the ignition charging coils resistance, and with the points closed a straight ground reading (very low ohms), are you sure your points are set to the proper gap? The way you describe works great on battery driven ignition coils with points, but we don't have that with this bike.

[UKKWF]

[davebike]

To set source coil type ignition with point like the pre CDI CG125 you need a multi meter with a sensitive Ohms range
as you did connect to the black wire and earth
Points open resistance will be a few tens Ohms and points closed one or two Ohms

Points should open / close at the F mark
Turn the rotor slowly as it will generate power in the source coil that will upset you meter
If you have the puller it is worth checking the mechanical advance retard inside the rotor is working and adjusted correctly

Dave
____________________
Dave
NC750Xdct + others at work !
[email protected]

[misscrabstick]

Set points with gap at the widest, ignore timing marks for gap setting.

[davebike]

misscrabstick have you ever set CG125 points ???

The ignition timing on the type of system is set by setting the gap

I only been doing this professionally for 35 years


Dave
____________________
Dave
NC750Xdct + others at work !
[email protected]

[UKKWF]

cheers davebike i will try with multimeter tomorrow... i have just installed the points and they are now set at 0.35mm gap on the F mark... bike still running like shit though... stalls after running for a while and given any throttle engine just dies... Any ideas on what to check next?? ... how would i know if the mechanical adv/ret system is shot or gone inside my flywheel??.. many thanks guys

[CG Sam]

Is it low on fuel or has it been recently?

Could be crap from the tank clogging up your fuel tap or jets limiting fuel flow.
____________________
CG125, SV650S, CBR600F, GSXR600 SRAD

[UKKWF]

[davebike]

Repeat
The points should OPEN / CLOSE at the F mark
IGNORE size of gap
Yes lots say set the gap but on a CG125 you set the timing by adjusting the gap

Adjust points gap so point open / close at F mark so slow running spark happens at F mark i.e. an the firing point !!

Easy

Dave
____________________
Dave
NC750Xdct + others at work !
[email protected]

[misscrabstick]

Most machines one would set the gap then shift the backplate to set the timing, I have never adjusted points on this machine you are correct.

A lot of the stuff I know is generic, and I will try and help people out.

So sorry you seem to think I am insulting you and your 35 years experience, you could have just said actually no it's like this on these bikes.

meh.

[UKKWF]

from what is seen in the video of the bike running and what ive written here... could the bike missing, running erratic and dieing when given the slightest bit of throttle be due to a weak spark??... when i ground the plug against the cylinder head though and kick over spark is bright blue just dont know if its strong enough???

[Fizzer Thou]

Ever since I had an ignition problem on my CB125S back in '75 I have suspected spark plug cap problems.This was cured by installing a new plastic NGK cap when it was found that the original was arcing the HT volts to the cylinder head and not to the spark plug.

If you have a multimeter,the plug cap should measure between 5 and 10 thousand ohms resistance.Check to make sure that the cap is not cracked.

When reinstalling the cap into the end of the ignition lead,snip off about 5mm so that the copper wires are clean where they join into the plug cap.Any corrosion will cause a misfire of some sort or another.
____________________
Just talk bikes.What else is there?

Always have a 'Plan B'

[misscrabstick]

OP, if you are getting a gap of .35 at the F mark and if Dave's 35 years of experience is saying the points should just be breaking at that point then you have a very big issue that needs resolving, set the points gap so they open at the F mark as Dave says and see if it improves things.

For the points to be .35 at the F mark the final maximum gap must be massively over big I reckon, and as a consequence the dwell angle and spark power seriously compromised as well as the ignition timing being horribly wrong.

[UKKWF]

[UKKWF]

Anyone know how i would check the adv/ret device inside the flywheel to make sure that its working as they are supppose to...?

[bypass2]

Does it run allright with the choke on. is there a good flow of petrol from the petrol tap. what about no air filter.that might solve it.

[Fizzer Thou]

[misscrabstick]

[Cyclingbiker]

I've had problems with my CG getting it to run okay when the timing was out and the way to do it is with trial and error to get the points to begin opening AT the F-mark. The gap is irrelevant as the gap grows or shrinks depending on the timing and how worn the points are. I became too focused on the gap size and completely missed the timing marks for ages before I got pointed towards them by some posts on here somewhere.

I used a multimeter set to the resistance setting and plugged one lead into the disconnected black and white wire coming from the points and the other one to a ground point on the engine. During most of the revolution of the flywheel counter-clockwise the points are closed and there is low resistance to earth but once the points begin to open the resistance goes up sharply as the path to earth is through the coil windings. Once I got it set so the points open at "F" everything was fine and dandy again.

Also I get the stock airbox put back on, having no filter on will cause the bike to run really lean and opening the throttle will make it lean out even more and kill the engine like you've described. If you can't get hold of an airbox for now try running it one half-choke to richen the mixture a little and see how you get on but get an airbox sorted ASAP.
____________________
Honda CB500s (1999) - Honda CG 125 BR-J (1991)

Mod 1 - Passed - 12/11/12 --- Mod 2 - Passed - 26/11/12

[UKKWF]

[Fizzer Thou]

Does the fibre heel of the points look worn?

The reason I ask is because years ago I was out and about on my CB550F and once at my destination and ready to leave the bike just would not restart.I checked the points and regapped them just to make sure,but the bike would still not start.Luckily there was a Honda dealer within a short distance and,after fitting a new set of points,the bike ran perfectly once again.

While you have your multimeter handy,have you checked the resistance of the plug cap?
____________________
Just talk bikes.What else is there?

Always have a 'Plan B'