Honda CG 125 2004 - Charging Issues

[rpsmith79]

Completed my CBT yesterday, so decided to have a few trips round the block this afternoon on my CG to get in some practice, and after about 20mins riding, i coughed and spluttered to a halt, tried to restart a couple of times but then the battery was flat, so i proceeded to push it the remaining way home

After about 500 yards i was knackered, so thought i'd give it another try, and low and behold it fired up again, so i rode it the short distance home, only for it to die on my again, and this time the battery was totally flat, would even turn over

So, into the garage, stick the battery on charge for 10mins, and it fires up again fine, so all is good there, but when checking out the voltage, it was around 12.5V when the bike was off, and then 11.5-12.0V when running, so something is amis with the charging circuit, but i'm struggling to get much further as to whether it is regulator/rectifier or stator related

I have done the rectifier diode check, and that all seems good, then i did the stator resistance check, and that shows resistances within the tolerances of the Haynes manual, so i'm still non the wiser........

......... anyone got any ideas what to try next before i start playing parts darts and replacing parts willy nilly

[neptune8]

Use your multimeter to check the wiring between the alternator and the rectifier/ regulator for continuity. Also check that the connections at the end of those wires are clean and sound, a dose of WD40 would not hurt. Incidentally, the power for the spark plug does not come from the battery on CG, but from one of the alternator coils. Earlier CGs like mine , which have both kick and electric start, can be started with a flat battery, or no battery. So if the battery is flat, you should still be able to bump start it. So although it looks like you do have a charging problem, that should not IMO cause the engine to die. As yours is a later model [which model?] It could be different tpo mine, so check the wiring diagram.
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[neptune8]

Just looked at the Haines manual, and if your bike is an ES4 or ES7 model, the power for the spark comes from the battery. You can check the alternator is working as follows. Disconnect the alternator from the loom. Make a 12 volt test lamp, and connect one wire of it to earth, that is engine casing. now with engine running at about 4K RPM, connect test lamp to each alternator output lead in turn. Lamp should light dimly [about 8 volts?] each time. If alternator is OK and wiring is OK, suspect reg/rectifier.
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[rpsmith79]

[rpsmith79]

[neptune8]

I would say that the reason your bike restarted after you pushed it is as follows. If a lead acid battery is connected to a load, but not at the same time to a charging circuit, the voltage will drop over time. If the load is then disconnected, the battery voltage will recover a bit over the next 15 or 30 minutes. This may have happened whilst the bike was being pushed, as the battery "had a rest". Once you restarted the bike, the battery was then on load as it supplied power for the spark. Soon afterwards, the voltage would drop again giving weak or no spark, and the engine died.
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[rpsmith79]

Yeah that makes sense

Cheers Neptune

[Teflon-Mike]

You are chasing a red herring assuming this is a charging issue.

CG's have a self exited 'magneto' ignition, which is totally independent of the battery. As long as the engine is turning, it should make volts to make sparks for the engine.

The 'generator' has three windings on the stator; one powers nothing but the ignition; one provides unrectified, unregulated volts direct to the headlamp.... which when the lamps are 'off' is redirected to the regulator to help charge the battery; last provides volts direct to the regulator to charge battery.

Battery ONLY actually provides power to the indies, stop lamp and horn, and significantly on later models the starter motor....

Make sense so far?

SO.. start at the top... dont do diagnostics by random or voodoo!

Your bike conked out.

With self exited ignition, if the engine was running.. then it should keep running... and if you had a problem with the battery or the generator, your headlamp might get dim, your horn might not work, your indicators might not flash... BUT the engine shouldn't conk out.

SO! There is one problem. WHY did it conk out?

Fact it started in the first place, implies there's the ingredients for life, but, in use 'something' went missing.... then after some time... came back all of its own accord, when it re-started.

Oh-Kay... well, I could take a pretty wild stab in the dark and suggest your tappets are probably wildly out of adjustment, and when warm, the clearances opened or closed up enough that the valves were either not opening or staying closed.... BUT, that is bordering on voodoo by ESP.... so do the job properly, and diagnose by logic!

First up; pull the battery, check the electrolyte level, and put it on a trickle charge. Better still, eliminate 'dumm' questions, order a new one and put that on trickle charge.

Whilst that's charging, do a FULL and proper service on the engine. Change the oil. replace the spark plug, and adjust the tappet clearances.

Find another 12v battery... one from a car, preferably not still attached to a car, or if so, certainly not with its engine running... and put the CG's battery terminals on jump leads off it, so you have an excess of amps to spin up the starter motor, and NOT deepcycle the bike battery before its given a chance.

Remember, CG's ignition is self exited, on start up, battery isn't providing electric for sparks; battery is just providing electric to spin the starter, hence the crank, hence the magneto, and THAT is making the electric for the sparks... SO if the engine doesn't get spin up quickly enough, you don't get the volts to make sparks... if so.... this MAY be a battery problem... may be a magneto problem, BUT could also be a starter motor problem...

Starter motor's draw big amps... nominal rating of a CG battery will be around 6Ah... which means it can accept or deliver 6A for one hour... if 'good'... starter motor will draw something more like 60A, which is why its powered on its own thick cable direct from the battery, switched by a solenoid... battery 'can' deliver that many amps, briefly, for maybe 1/10th of an hour, 6min... in theory...

In practice, that rate of discharge will make the battery 'boil' the electrolyte, and it's volts will drop, in maybe 2-3 min... leave it to cool and the electrolyte will 'settle' and you'll get volts back, and might be able to start again, and get another minute or so from it... BUT, this is 'Deep-Cycle-Discharge' and repetitively discharging the battery that heavily that often, WILL kill the electrolyte....

Little bikes have little battery's, and marginal charging systems... and the CG suffers from not being designed to be an electric start motorcycle, back in 1976, it has been 'adapted' to make it e-start...

NOW, fresh off CBT... first; I doubt very much you have been thrashing the thing very hard, and I would suspect, from comment you are not a fresh-faced teen ager, but an existing car driver... in which case very very likely car driver habbits have added to new rider ones, and you have been loath to let the motor 'scream' to your ears and have been using low revs and short shifting, using higher gears, and low revs, in your brief ride, which wont see the crank hence magneto turning too fast for very long and best able to provide the volts to charge the battery... which, will have been pretty well depleated by 'first start'.. and more so, I suspect from lack of practice in starting procedure.... especially so if you are a car driver used to fuel injected cars that start on the key, and have not had to fathom a manually operated choke... which is a bit wampy on the CG.. THEN following 'advice' in the class-room, and the safety schpiel over 'conspicuity', I'll lay odds on you riding with the headlamp 'on' all the while.... so the battery will only be gettiung charge from that one winding, and not given the 'spare' from the headlamp.

Hint: If it aint dark... dont use the headlamp! for conspicuity, if you want to light up the headlamp bowl, use the side-light only, on this bike.

However... it IS a common niggle; learners dont give the bike best chance for the battery to charge, from starting clumsiness, through riding inconfidence, and using headlamp as Day-Time-Running-Light, and often lots of clumsy clutch control and 'stalls' and re-starts, hammering the battery on the e-start....

Bike batteries, dont last.. they are small, and the amps starters suck is much bigger in relation to their capacity than on a car; they tend in regular use to only have a 'life' of around two years, rather than four... but, this sort of learner use, and repetitive deep-discharge on the e-start, marginal charging and riding less conducive to giving it best chance of ever being fully charged, and then likely periods of 'lay up', they can be dead a lot sooner... and on a budget bike like teh CG bought on the legend they are 'cheap' and 'indestructable' they are likely NOT to get new ones very often.

So.. good chance your battery is a dodo... but, whether it is or not, or if you get a new one... you DONT use it to do diagnostics, deep-discharging it on the e-start to spin the motor over to test sparks or compression, or you are as like to reduce whatever life it has before you start... HENCE doing the diagnostics off jump leads from a car battery....

BUT... car alternators deliver perhaps 17.5v regulated... IF the car the battery belongs to is running... bikes generator delivers unregulated volts, that are regulated at aprox 13.5v.... slap jump leads off a car on to a bike battery, and the 17.5v the alternator delivers, will get regulated by the bikes regulator... which is NOT designed to ever see that many volts, very often, or for that long, and it CAN fry them.. quickly... SO, you dont jump off a car with the engine running....

BUT car battery should a) be fully charged! b) have excess amps to power starter for diagnostics, c) do it without such risk of deep-discharge damage d) do it for longer without going flat and having to be recharged!

Hint: if doing lots of diagnostics; charge car battery by running car engine periodically BUT, remove jump leads from bike before starting car!

This, though is advice behind suggestion to get a new battery; they are a service spare, and it is likely the bike will need one, sooner or later, it is likely the battery is well past its prime, and if also likely that effing about trying to fault find will kill it if it isn;t already on the critical list.

Oh-Kay.. so tappets adjusted, spark-plug replaced, and a 'good' power supply for the starter motor.... spin it up, spark plug out the hole, metal of plug given a good earth, either rested on an engine fit, better (safer!) if held in the croc clip of another jump lead, the other end clipped to known good earth on the frame, or battery.... and look for healthy spark across the gap.

While plugs out... and motor spinning... check compression... if you have a compression tester, this is useful, but make sure that the throttle is wide open, and engine can actually suck in something to compress. If not, same deal on the throttle; but rule of thumb is if you can hold your thumb over the spark plug hole... you probably don't have enough compression!

If you have a healthy spark; and cant keep a thumb over the hole; have adjusted tappets and changed the oil... you are probably good to go.... fit battery and 'go'...

Any faults or problems you have after... are at least base lined... BUT good chance you wont have any.

IF with the motor serviced and you have trouble re-starting.... remember.. BEFORE diving in to blame the bike, and pulling electrics to bits or tearing carburettors apart..... LEARNERNESS... if you are using DTRL's, if you are doing lots of starts and few miles, and aren't letting the engine breath, short shifting, using gears not revs on the road... you WONT be giving it a chance to charge..... so start there again!

On topic of short shifting... DONT DO IT... just dont. just because you have five gears doesn't mean you have to.

That little motor only makes about 10bhp on a good day, and that only at 10,000rpm! under 3K you are probably shifting at you likely have less power than a moped! enough to do 30mph, even in top gear... BUT, you are denying yourself 'throttle response' in the process, and making the engine labour. you are not saving fuel or wear and tear.. power is torque times revs, IF you need 3bhp to go 30mph, you need 3bhp.. if you dont use the revs to get it, you have to use more throttle to get more torque, so you are putting just as much 'strain' on the engine, and using just as much fuel.. and its an 'ecconomy' 125 ffs, its not like it's drinking the go juice at a rate that has opec Sheiks wringing thier hands with glee to start with! Use the revs NOT the gears, give it a chance to charge the battery; give your-self a chance to change speed, on the throttle and have that throttle response to do so, AND save so many oportunities to muff stuff up having to make so many gear changes so often.... you WILL ride more smoothly NOT changing up, demanding you have to change back down again!

And dont go chasing re-herrings when you have a problem.. and remember.. whilst its an old learner bike, and they do tend to suffer... there's as much chance you are doing as much wrong as the bike at the moment!

And 'this' is a non problem... in which you are as to blame as the bike, and theres absolutely NOTHING wrong with your reg/rect, or your magneto... there may... BUT, there's definitely not enough to say so from the symptoms, and an awful lot to suggest you look elsewhere first.

DONT do diagnostics by random or vooddoo! Get the book and follow the logic, and base line 'problems' from the top eliminating variables starting with the simple... and remember, simplest, at the moment is probably the user
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[rpsmith79]

Cheers Tef, all good info

On the subject of running with the headlight on, unfortunately i have no choice over that matter AFAIK it can't be turned off, i only have a dipped/full beam switch. Saying that, i have replaced the old incandescent bulb with a more modern halogen bulb, so this could be having a bigger draw on the battery

When you say tappets, i assume that is the same as valve clearances, but yes i will give that a try too, again it would make some sense as i guess my time pushing the bike would have allowed the engine to cool and valve clearances relaxed, hence why it started and ran again briefly

And yes, you are correct, long time car driver (20 years) so have been short sifting and using lower revs

So are you saying that the stator/magneto will not actually charge the battery until over about 4000 rpm, as stated above, the battery on its own was reading 12.5V, and when running (on idle) was only around 11.5V, do i need to build the revs up to 4000rpm to see if that alters the voltage?

[rpsmith79]

Oh, and for reference, here is the wiring diagram for my bike

[Teflon-Mike]

[rpsmith79]

Well i nearly got the tappets checked this evening, got home from work, dismantled the bike to get to the rocker cover and drivetrain to get to TDC, then went to grab my feeler gauges, only to find that i appear to have lost them, so will have to wait till tomorrow when i can grab myself a new set

Will report back tomorrow with my findings from that

[rpsmith79]

Checked valve clearances, and there is something very weird happening

Please see my new thread

https://www.bikechatforums.com/viewtopic.php?p=4419522#4419522

[rpsmith79]

Right then, panic over regards valve clearances/tappets........ phew, thought i'd goosed the engine there for a moment

Anywho, fired it up again (which seemed to start much easier than usual) and even after letting it run for a while till i could run with the choke off, i was still only measuring 12.0V with the bike running and giving it revs, on 12.5V when bike turned off

So surely there must be some sort of electrical gremlins in there somewhere (though still debatable if this caused the engine cutting out)

[jaffa90]

Your battery sounds fine but the charging system is not working so check the wires from the reg/rec in and out.

[rpsmith79]

Well i don't know if it's solved the original issue of the bike cutting out, but after replacing the reg/rec with a 2nd hand one off of eBay, my charging problems are no more

Now i get a healthy 13.5-14.0V when the engine is running

Just need to wait till the weekend (too dark to ride it when i get in from work) to see if i have solved the original issue

Fingers crossed

Saying that, looking again at the wiring diagram, all the power from the stator goes into the reg/rec, then to the coil, so if the reg/rec was at fault, it would surely have implications on keeping the engine running

Oh, and thanks everyone for your help, learnt quite a bit already from this forum, cheers

[neptune8]

That was my conclusion on looking at your wiring diagram- Battery provides the power for the spark, unlike early CGs like mine, which will spark and kickstart with no battery. Pleased you have resolved your problems.
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