Help with points and timing

[eazy rider]

I've been trying to fix my cg125 (https://www.bikechatforums.com/viewtopic.php?t=174931) and I've narrowed the problem down to the contact breaker assembly.
I need to know exactly where to find the contact breaker gap so I can check it with my feeler gauge.
I do have a haynes manual but to be honest the description and pics are useless unless you already know what you're doing.


Is this the gap I should be measuring (inbetween the outside magnet plate things and the plate that moves over the top of it)?

[stinkwheel]

No. The points are usually more at the 10 o'clock position under that flywheel.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[eazy rider]

Could all the dirt and crud on the magnet plates have something to do with the poor running of my bike?
You can see clearly in this pic there is quite a bit of grime and little black specks all over the plates (contacts?).

[eazy rider]

The Hayne's manual says:

"Rotate the engine until the contact breaker fibre heel is at
the highest point of the cam and the points are at their widest
opening. Examine the contact faces"

Which part is the contact breaker fibre heel? I don't see any fibre parts on the inside of the rotor that move round. Only magnets.

The only fibre part I can see is a little circular pad in the metal contact point that is screwed in between the two big exposed coils.

I've taken a pic of it here:

[eazy rider]

stinkwheel, the contact breaker you posted looks different to mine.

Here is a pic of the one I have. Could you show me exactly where on this little bastard I need to check the gap?

Also, I take it the gap opens and actually closes at certain points in the rotors rotation is this correct?

[The Artist]

top arrow is where the main rotor pushes on the points to make them open.

Arrow marked gap opens and closes. It needs to be fitted to the engine before you can set the gap

[eazy rider]

Thanks for the help guys I think I understand most of it now.

There is still a problem however. At no point when I rotate the rotor do the points actually open. They seem top be stuck closed through the whole rotation.

I can push against the points and they will open and spring back into the closed position. How the hell am I supposed to check the gap when there is no gap to check?

If the points are somehow not opening would the bike even start or run at all?

This is driving me nuts lol

[alun111]

This is something I've got to do on the cg soon too. As far as I can understand the contact points will only open 0.3-0.4mm anyway... so I don't think you'll see the physically open. Someone correct me if I'm wrong though!
____________________
Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70

[eazy rider]

You're right they should only open 0.35mm.

I did look up close with a torch shining onto it and I'm pretty sure it never even cracked open.

[stinkwheel]

[eazy rider]

Cheers stinkwheel, I'm off down the motor shop to pick up some emery paper, oil and a multimeter.


"They run like shite though."

That describes it to a T

Hopefully I may have this sorted in a couple of hours.

[eazy rider]

Well I've adjusted the contact point gap so it actually opens now. The bike was even harder to start than normal although I'm not sure if the gap is exactly right...it is a very awkward fit for the feeler gauge through that tiny little rotor hole.

I may have another problem (or this may be the root cause) when I was kicking the bike over sometimes the kick pedal would lock up like it was in gear and then on the next kick it would move halfway down without any resistance at all.
What could be the cause of this?

[Pete.]

The points gap dictates the ignition timing. If the gap is too wide the ignition will be advanced (spark will fire early) and if they are too close the ignition will be retarded (spark fires late). The CG125 is very tolerant of ignition timing errors though and simply having a gap is enough to make it run.

Once you set the gap, you can check the ignition timing using a small bulb (I used to use a dashboard bulb out of a set of bike clocks). You connect the bulb to the points wire and then to a battery +, and connect the battery - to the bike frame/engine. When the points are shut the bulb is on and when they open the bulb goes off. Turn the engine over slowly by hand (spanner on the flywheel nut) and the bulb should go off when the F mark on the flywheel lines up with the mark on the engine case.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[eazy rider]

Geri, thanks for the information.

I am using a multimeter.

I know I need to connect one of the wires to the black points lead but where do I connect the other wire?

I've tried connecting the other wire to various points like earth, battery etc. but the reading is still the same.

When the rotor turns to the 'F' mark the points are clearly open but the multimeter still shows numbers on the screen. I can even push the spring way off the contact point and there is still a curent registering on the meter.

[stinkwheel]

There is also the old fashioned, not quite as accurate technique.

With the engine just before the F-mark, seperate the points and slide the corner of a cigarette paper between the contacts which will grip it when they close. You should just be able to remove the paper without it tearing when the firing mark lines up.

Now check the gap. If it is outside the allowable tolerance with the timing bang on, your points are worn out and need replacing.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Pete.]

If you're using a multimeter then connect + to the points wire and - to the engine and measure the voltage with the ignition on (and all the wiring connected as normal). When the points open the voltage will shoot up.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[eazy rider]

Okay this is strange. Now my bike won't start and there is no spark from the plug as far as I can tell.

I've done exactly as described with the wires and the numbers on the multimeter stay pretty much the same no matter what position the rotor is in.

I can see that the contact points are opening and closing but the reading never shoots up like you said.

Shouldn't the meter reading return to the "1" symbol meaning the circuit is open when the points aren't touching? Just like if you used a bulb setup it should turn off right?

The reading always stays around 02.3 - 10.5 depending on where I ground the multimeter wire (engine, earth point etc.)

I mean if the points aren't touching each other then how can there still be a reading on the multimeter?

[Pete.]

If you are using a multimeter to check the points you leave the wiring intact and the ignition on. When the points are open you should show near 12V at the points. When they close you are effectively grounding the coil to produce a magnetic field so the voltage will go right down. So when the points open, the voltage at the points shoots up to about 12 as you are not powering the coil and the field collapses producing a spark.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[eazy rider]

Thanks for simplifying that for me Geri.

One more question.

Should the voltage stay very low right until the rotor gets near the 'F' mark or should it gradually increase as the points open?

I haven't seen the actual cam so have no idea how it acts on the contact points. Is it a gradual opening or does it snap open just when it's near the 'F' mark?

I apologize for the endless questions...this is the first time I've worked on an engine.

[Pete.]

Points open quite quickly but not 'snap' open. Pretty-much like a valve opens except with much flatter wider lobes. The cam will be on the hub of the rotor.

The voltage will stay low until the F mark then jump suddenly. If you turn the rotor very slowly you might see an erratic reading as the points crack open.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[eazy rider]

I checked the timing but something seems to be wrong.

No matter what position the points are in the voltage always stays low and will not shoot up.
I have the keys in the ignition and tried the indicators to make sure the battery wasn't flat.

I can open the points with my finger and the voltage stays exactly the same. Anyone have an idea why this is happening?

Here is a pic just to show exactly what I mean.

[eazy rider]

Also, I've ordered some new points from David Silver but there are 2 types.
One set of points is for the 2 coil version and the other for the 3 coil version.

I take it they are referring to the number of those big coils on the stator plate right? There are only 2 coils on mine which is why I ordered the 2 coil points.

But now after seeing pictures of the 2 coil version points they seem to be different to mine whereas the 3 coil points I've seen look the same as mine.

Should I ring them back and tell them I want the points for the 3 coil version?

It's a 1980 CG125 K-1 model btw.

[robocog]

I'm not sure about the more modern CG's but certainly the older ones with points - there will be no voltage on the points till the engine is physically running as its the generator that makes the eleccy that goes to the points
(it appears it should be AC if coming straight from the generator, with no recifier or regulation as well so perhaps thats why with points completely shorted they will still run?- just a theroy)

put your new shiney multimeter onto resistance (ohms) and measure from the points to the engine case
ignition in the off position there should be a dead short no matter what the points are doing
igntition in the on position, points open there will be the resistance of the coil that generates the electricity- (a few k ohm at a guess?..the book of lies does not even suggest what it should be)
igntition in the on position again - but points closed it should read short (zero ohms)

Have popped an electrical diagram for the simples cg's on my website
https://www.robocog.dyndns.org/cg125/simplecgwiringdiag.jpg

Its the first time I have come across an ignition system that does not provide batt voltage across points with igntion on and not physically running - but then I am new to 2 wheeled stuff
It took me by surprise but can see why Honda did it and think they chose a pretty neat path to keep it as simple as physically possible

Hence why the book of lies suggests using a battery and bulb to set the timing, rather than just a bulb

Good luck sorting it out- will watch the thread and help where I can
If you need more manual scanning and hosting shout me


Regards
Rob

[eazy rider]

"measure from the points to the engine case
ignition in the off position there should be a dead short no matter what the points are doing"

By "short" you mean the screen should read as an open circuit and display the '1' rather than the voltage right?

My bike doesn't do this, the reading will simply drop from say 0.8 to 0.7 if you turn the ignition off.

The reading simply will not shoot up or go back to '1' or 0.00. It just basically stays in the same range no matter where I put the multimeter probes or if I have the ignition on or off.

The only time it really jumps and changes much is when I rotate the rotor it will dart up and down but returns to around the same reading every time.

So if it's only the multimeter powering the circuit then should I just be looking for it to jump to say 2.00 or 3.00 from 0.8?

Another thing that affects the reading is where I put the probe on the engine. In some places I'll get a steady reading of around 8.00-10.00 and in other areas like in the pic above it stays pretty low.
Exactly where should it be placed for the correct reading?

btw thanks for the wiring diagram but that is an alien language to me I'm afraid.

[robocog]

OK have re-done the ignition side of the diagram, pretty damned simple eh! without all the other stuff going on

https://www.robocog.dyndns.org/cg125/cgignition.jpg

Just to clarify when set to measure resistance (Ohms- or K ohms - omega symbol)

dead short = multimeter will show as good as 0.000 Ohms - same as when you put the two probes together

open circuit = same as waving the two probes in thin air -multimeter will show O.L if its like mine (think its trying to say Over Load?) but yours may show something else

Regards
Rob