Please help Honda CG125 running probs Easy fix for you clever guys!

25 posts / 0 new
Last post
Please help Honda CG125 running probs Easy fix for you clever guys!

Hi guys,
Just bought a Honda CG to do a little commute on. Picked her up and had instant problems.... it cut out 2 miles from pick up. After that i couldn't get any ignition (no neutral light or bike lights when engine not running but ignition on.) So i replaced the battery for a tenner and that brought back the ignition, good spark, and my lights worked just off ignition.
LOL that got me running for another few miles, she cut out again! (it kinda coughs splutters, few back fires, absolutly no power then cuppla hundred metres later she dies.) I bit the bullet and took her to a garage, worked with the guys, had the rocker cover off they wern't happy with the clearance at the top of the valves, so we set them up. We cleaned the carb, and they were happy with the carb. Mechanics wern't very happy with the compression said it was quite weak (that was only feeling off the kick start). But with me being tight i told them to ignore that for now, i just wanted to limp home and get a post on here!
So I was back on my way..........got about 25 miles this time, then i had the same failure as the previous time, cough splutter, gradual loss of power. Any higher gear than 3rd and it wudda died instantly, i stuggled in 2nd for about 300 metres then power ran out all together and it stopped. Oh and after the stop it's literally imposible to start again, i had to push the last mile to my house. But i left it for a few hours then i cud just about get it started again after bumping it, but it will die quite quickly, and now im not gonna take it on a run till i've changed something!
Right then, whats every1's thoughts? These are simple beasts, and are very few things to go wrong. Im quite drawn to the coil & compressor and then the rectifier. I believe these all have an affect on keeping the battery charged, starting and keeping a good constant spark whilst running?
I'm slightly worried about this compression issue, but wud that give me my symptoms bearing in mind my exhaust smoke is ok and i covered a good 25 miles of fault free running. Air filter is clear ish, there is plenty of fuel, and a good battery.
Any suggestions are greatly appreciated, and CG owners with similar problems would be fantastic!!!

Many Thanks

Charlie

Electrical, almost certainly, charge the battery and check the voltage across the battery while running, should be no less than 13 volts, if it's lower, it's the alternator or the reg/rec thats FUBAR'ed.If it's compression, it wouldn't run at all.HTH!BTW, It's hot in here, I'm thirsty!

www.electrosport.com/electrosport_fault_finding.htmlIt'll be the generator or the reg/rec. Take a look at the PDF here. You got a multimeter?

yup, sounds like electrics. But that's what I thought before I sorted the points/capacitor, coils, HT leads and plugs on my similarly simple BMW. Twas actually the fuel filter in my case... I wouldn't have thought it, because it always worked when cold/had been standing for half hour or so. (just enough time for the carbs to fill up). Take the plug out and crank it over? Is the plug wet when you take it out? If so, you've got fuel. Does it spark? If so, you have electrics. Do the same when it dies. What's changed? If sparks gone, change the plug, work backwards eliminating things. But probably do the reg/rec first. I used to have a CG125 (superb bikes, the happiest days ) and so I know you can get most bits v. cheap on ebay. fix and enjoy!(And get the drinks in NOW)

Like said before, it's the leccys! Squags, you should have a link pipe between your carbs at the bottom of the airbox, it's pretty unusual for both filters to clog at once!

Bigjawa wrote

Like said before, it's the leccys! Squags, you should have a link pipe between your carbs at the bottom of the airbox, it's pretty unusual for both filters to clog at once!

I do! But it's a R65 - the one with only 1 fuel tap! In the end there was sooo much crud in the tank I bought a newly cooly painted one off ebay for £20.:burnout:

Squags wrote

I do! But it's a R65 - the one with only 1 fuel tap! In the end there was sooo much crud in the tank I bought a newly cooly painted one off ebay for £20.:burnout:

That was ok! Forgot the R65 was an oddball!

Sorry i didn't mean "coil & compressor" i meant "coil & condensor" She's got more than half a tank of fuel in it, although im slightly worried it cud be pulling crap through it coz it was sat up for 4 months with a tiny bit, but i topped her right up with optimax. Choke is deffinatly off, i've checked and double checked with lots of ppl, and then pulled off the air filter pipe to have a look at the gate for peace of mind. Having the engine rebored or fitting new piston is the last thing im going to try, i want to try everything around it 1st thats cheap and easy. When the engine is running, she actually sounds alright, massive flat spot at 55, and she wont go anywhere. 60 down a hill. But thats the same with every CG. Only had the plug off once, and it showed signs of overheating (whitey) haynes manual says thats caused by ignition system fault, incorrect fuel or cooling system fault. So thats where im upto today (saturday the 3rd june) Im about to pop out to buy a new spark plug, and a cuppla tools i need. I've ordered a new coil & condensor and a rectifier off e bay. Anymore suggestions greatly appreciated. Charlie.

I know this might sound daft, but have you checked all the tubes coming from the fuel tank to where there supposed to be, i know on mine I forgot to connect one after I took the tank off my bike and had similar problems as you described, but if you took it into a garage i think they may have checked that. Maybe?

Why don't you tell us where you are, and see if any of us are local? I had a CG, and have a bit of mechanical nouse, and I bet most of us in here can say the same.

There is only 1 pipe coming from the tank, which is after the tap, and that goes into the carb. That is all fine. 1 thing i forgot to mention on my previous post, when i had a multimeter hooked upto the battery when the engine was running, i was getting between 13-14 volts normally, but on occasion, it did go a bit crazy and drop quite low, and it was in the low 12's when the indicators were on. At idle it was only just reading 13 I'm a little worried that when i checked it the coil was behaving well, but if i cud monitor it when i kept breaking down, i suspect i was losing it all together. I'm hoping all these things are pointing towards the coil! I've bought a coil on e bay today, i hope it arrives soon.All suggestions still needed, im making a list of things to check, if this coil doesn't work, i'll be working through the list until it's fixed, or until it drives me insane and i throw it in the river!! lolCharlie

Just a quick suggestion if this isnt fixed yet..Checked the Spark Plugs? and the HT Leads? Spark's should be nice and clean with little fouling. If heavy fouled - can cause Backfiring. Dont ask me how, I know it just does. Not too sure on your neutral light problem... are you sure the bike is deffo in neutral? I.E can you start the bike without holding the clutch. If you can, check the neutral wire is in the connector block properly as it may have come loose. Also - its worth doing a general maintenance on it, check oil levels, check all connections are nice and tight. Might be worth investing in an Haynes manual. Could be picked up for a 5er of eBay I reckon. I had a similar experiance, but on a CB125TD-C - similar to a CG but its a Twin.HTHOh, just an after thought. Check the oil filter isn't blocking up too. I had that, and caused major problems The guys on here will tell you

Squags wrote

yup, sounds like electrics. But that's what I thought before I sorted the points/capacitor, coils, HT leads and plugs on my similarly simple BMW. Twas actually the fuel filter in my case... I wouldn't have thought it, because it always worked when cold/had been standing for half hour or so. (just enough time for the carbs to fill up). Take the plug out and crank it over? Is the plug wet when you take it out? If so, you've got fuel. Does it spark? If so, you have electrics. Do the same when it dies. What's changed? If sparks gone, change the plug, work backwards eliminating things. But probably do the reg/rec first. I used to have a CG125 (superb bikes, the happiest days ) and so I know you can get most bits v. cheap on ebay. fix and enjoy!(And get the drinks in NOW)

thats what i was thinking, its just running off the fuel in the carb then dying. run some fuel system cleaner through it just incase, only a few quid

if you click on search this forum, click advanced, & then stick designz into find posts started by you will be rewarded with a wealth of information. Particularly in regard to the oil filter & what happens when it's gummed up. You could also stick your model into keywords & see what else appears.Good luck & a strong coffee ana sticky bun for me please.

Hi guys, tonight i have drained the oil, cleaned the oil filter gauze, there were a few metal shards in there but nothing mega. I can't get at the centrifugal oil filter, damn screws are far to tight for my puny screwdriver. Ermm, i drained the fuel, and im not happy with the fuel tap at all, when in the on position, it has got a really random flow and i cant get at the fuel filter gauze coz the alan screws are knackered, so im gonna buy a new fuel tap. Apart from that, i set up the valve clearances properly and checked the points, both perfect. Bad news is the sump thread is knackered, and 1 of the threads in the rocker cover is knackered. Is it worth having these tapped, or is lock tight and witness marks the cheap and fast option, perhaps even sum locking wire on the sump plug? Whats every1's opionion on my stripped threads. Think i'll have the running problem sorted soon.Many Thanks Charlie

err, well my opinion, FWIW, is to do the job properly, so I'd be soaking those centrifugal screws in WD or whatever, buy a decent screwdriver (old knackered electric ones obviously have a thick handle which allows for really good torque in your hand) & tap the threads.

Your original problem is due to the battery not being charged. All the messing about in the engine with clearances and the cleaning of the carb, fuel filter etc... is pointless. - When it konks out you have no electrics right? So it's absolutely nothing to do with valve clearances or fuelling!Either there's a loose connection between the generator and the battery or the reg/rec isn't working. As suggested above, check the voltage across the battery terminals when the engine is running, if you're still not convinced, run it til it dies then get it jumpstarted and you'll see you can start it and run it for as long as you like on the donor vehicle's battery.

blessmycg wrote

www.electrosport.com/electrosport_fault_finding.htmlIt'll be the generator or the reg/rec. Take a look at the PDF here. You got a multimeter?

Ahem What he said^^

put it this way its fooooooooked

cg125 mechanic wrote (see)

put it this way its fooooooooked

Yes - it WAS foooooooooked four fooooookin' years ago. It has probably been fixed by now.

HI    I HAVENT BEEN ON A BIKE FOR 31 YEARS ,BUT I DECIDED TO DO MY CBT   LAST WEEK AND GOT THROUGH IT O.K. THE LAST BIKE I HAD WAS A SUZUKI  AP 100. IT RAN ON PETROL AND HAD A 2-STROKE BOTTLE SEPERATE. I HAVE  BOUGHT HONDA CG 125 , BECAUSE THEY GET A GOOD NAME. ITS A 08 PLATE,  WITH ONLY 180 MILES ON THE CLOCK. ITS BEEN ON SORN MOST OF ITS LIFE.  IT HAD A FLAT BATTERY , BUT WEE BUMPED IT AND AWAY IT WENT. I PICK THE BIKE UP ON FRIDAY. I KNOW ABSULUTLY NOTHING ABOUT THE BIKE. DOES IT RUN ON UNLEADED PETROL ? IT ISNT EVEN RUN IN YET, ANY ADVICE ON THAT. DO YOU USE 2-STROKE OIL LIKE MY OLD BIKE ? ANY INFORMATION WOULD MUCH APRECIATED.                                     THANKS DAVIE.

Oh dearEven 31 years ago a CG125 would run on unleaded so yes.It ain't a 2 stroke.Do you drive a car?Oh and please start a new thread instead of digging old ones out of the gutter.

Welcome back to biking! The CG125 is a humble machine, but honest and worthy enough!It sounds like you don't know much about bikes (no shame there, otherwise this workshop forum wouldn't exist!), but the CG is a very simple machine so ideal to learn basic mechanics & spannering on! Best way to do this is to get a copy of the Haynes manual for it - typically about £18 from bike shops but should be able to pick up a copy on fleabay.Ideally you'll do work on the bike with an experienced friend (it's much easier to learn to do things the right way, that keep cocking things up and learn how to un-do mistakes), but as I say, the CG125 is very simple.As Doof says - it's a 4-stroke so no need for 2-stroke oil, but you will need to change the engine oil every few thousand miles or every year (depending on the miles u do). As it's been standing for a long time it would probably benefit from an oil change some time soon, but as long as there's enough it it, it should be OK for now. There are many debates about running in new engines - many riders of high power sports machinery advocate virtually zero running in, but not having fancy coated bores, slipper pistons and modern bearings I suspect the CG will benefit from some running in.Ideally it's done on loong runs - several hours so that the engine gets good and hot. During this time you vary the engine speed & load, starting with light loadings / low revs and gradually increasing both over a few hundred miles. On the CG this will be quite difficult (and dull) as it's got so little power anyway that using the engine "gently" will see you barely above 30mph! As part of this process you should change the oil at 500 miles - after standing for a year it'll be breaking down a bit anyway! Don't be tempted to replace it with incredibly posh oil for the first oil change - it'll not help the running in process.Again, as Doof says - unleaded is fine, and as I recall those things eek out about 120mpg once fully run-in & settled.You can do searches on the forum for old questions / answers, but if it doesn't solve ur question it's generally best to start a new thread. The only stupid question is one that you don't ask! We're usually a helpful bunch on here but don't suffer fools gladly that ignore advice, and "txt spk" seems to annoy a few too!How long do you imagine you'll keep the CG? Are you just using it long enough to do your tests? Or keeping it as a cheap commuter?

HI DOOFFE9                   THANKS FOR YOUR REPLY IT WAS HELPFULL AND                    YES I DO DRIVE A CAR, BUT IF YOU DONT AS IN                    IN THIS LIFE , ITS TO LATE IN THE NEXT.  KNOW                    MATTER HOW STUPID IT SOUNDS. I KNOW AS MUCH                    ABOUT COMPUTERS AS I DO ABOUT BIKES ,BUT AT                   LEAST I KNOW WHAT A THREAD IS NOW. I THINK. HI TAPPY                 THE INFORMATION YOU SENT ME WAS VERY USEFULL I               AM GOING TO GO FOR MY TEST, POSSIBLY NEXT YEAR,               IM USEING THE CG TO GAIN SOME CONFIDANCE AND GET               EXPERIANCE BEFORE HAND . IM NOT  REALLY INTO BIG BIKES               BUT WOULD LIKE TO GET RID OF THE L PATES AND HOPEFULLY               GET ARROUND A 250CC . THANKS FOR YOUR HELP.                                                                                              DAVIE                      

did you ever get to the bottom of this issue? my cg started making the same kind of noises and now wont run. it starts and there is compression. but it wont idle. i have to keep the throttle on or else it just cuts out. any advice would be helpful.  this is my first bike and i am really getting to grips with its working before i move on to some thing bigger.   thanks in advance.

Log in or register to post comments