Honda CD125 Benly - Does not stay running?

[nazK]

Hi Forum,

I am new here and also a new owner of CD125 Benley from 80s. I have a rough idea on what's what on the bike but have no clue when it comes to follow a step by step elimination process to fix the underlying issue.

I bought the bike form someone who put an mot on it and said it is also serviced, I got the bike delivered today and the delivery driver started it first time and showed me engine running and that's that. I accepted the delivery.

Now after couple of hours it turns over but will not stay running. All lights are working, horn is working and I also asked the seller on the phone if there is anything I need to know he said battery is fine I just have to play with the choke and throttle as he advised but it did not help. It was supposed to be serviced by the seller. I doubt some of the things seller is saying about the service because the oil is very very black and it is not even that sticky. Therefore I am going to take a fresh start on fixing it. Hence I am not even sure if battery is my issue since seller will never say that it may be because he said he put a new battery also there are other things he promised and never did so I do not have any trust in what he says going forward.

where do I start before going to a mechanic please, I love this bike and they are becoming rare?

Thanks
Naz

=======
This is what seller said and advised:

The bike has also been ridden it requires full choke from cold to start and quarter throttle. They take a while to warm up so return choke gently until warm the fuel may also need to be turned on
Service Work:
The service including oil. ht caps. spark plugs .drive chain adjust and lube . battery charge .Tyre pressures . head race bearing adjust .brakes adjust. air filter.the cleaning of the carb was cleaned because bike was standing for two years and would not have run if it was not cleaned and the fuel tank washed out with fresh fuel. but stripping the carb is not part of a full service

also when you try to start make sure that petrol switched is on.
Quarter to half throttle full choke and start the battery should not need charging also you may have fluid ed it try without choke
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NEW TO BIKE MAINTENANCE- HAVE CD125 BENLY

[nazK]

Update:

when i start it it comes alive but do not fire up, i have to keep holding the start button to keep it alive and soon i let go off the start button it dies. The choke and throttle do not make any difference while doing this.

also there is some noise when I am doing all above which seems to be coming from the top/head part of the engine side i can be wrong, the noise stands out and sounds like hammering on the metal if this makes sense.
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NEW TO BIKE MAINTENANCE- HAVE CD125 BENLY

[Hong Kong Phooey]

Have you tried wiping it away with a tissue?
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'81 CG125, '97 FZS600 : '99 CBR600F4, '09 KTM RC8

[nazK]

[nazK]

Update:

while playing with choke and spinning it over and God knows when why and how it did fire up for a short while and then back to same issue.

Now it will not even do anything, now when i press hold the start button I hear some ticking noise near the battery which I believe we now have a flat or too low battery and noise is coming form starter relay...
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NEW TO BIKE MAINTENANCE- HAVE CD125 BENLY

[Nobby the Bastard]

[Rogerborg]

[nazK]

[nazK]

[jaffa90]

Does it have a kick start?
Are the spark plugs wet with fuel?

[Chris45]

Leave it for a few hours. Sounds like you've flooded the carbs.

Is the fuel tap in the Run or Res position?

If the battery has been discharged completely due to excessive cranking, you'll need to recharge it.

Alternatively, if there is a residual charge, i.e., ignition light - then try bump starting it. Get a pal (the wife will do) to push it as hard as possible, hold the clutch in, put it into 2nd gear and drop the clutch whilst opening the throttle.

Sometimes dealers say a bike has had a "recent service" when in fact it was twelve months ago, by the previous owner!

If the oil is really black and sooty it needs changing.

Don't blame Sooty
____________________
Honda CG125>Suzuki GT185>Honda CB 250N>Suzuki GSX400>Honda CX500B>Kawasaki GPZ305> Kawasaki GPZ550>Kawasaki GPZ500S+BMW 650GS

[nazK]

[nazK]

[Teflon-Mike]

First UP by the haynes manual - you are gong to need it.

Seconds.. the 1980's was quite a long time.... and saw the CD125 updated a few tmes, from a 6v points ignition motor, through to a 12v CDi igntion motor.. it also gained an electric self starter.... so narrow things down a bit... identify what you have... and DO NOT assume that because t says CB125 Benley on the side-panel and has a reg plate that has say a 'B' pre-fix issued in 1983, that that is the year the bike was made, or that the bike still has ANY of the bits it was fitted with in the factory, whenever it was allegedly built....

Next up, its an old bike..... t was probably first used legally on the road before I was, and I aint no spring chicken! It's got a log hstory, and little learner bikes tend not to fair well n the hands of know little learners; there s every liklihood that what you have, has been thrashed, crashed and trashed by more than a few owners, and between times been layed up derelict for long peroids to rust in pieces.... before this latest 'resusitaton' that doesn't eve make claims at any 'restoration'...... and done little but get t making motorbikie noises and a MOT man happy......

Cutting to the chase, I would, from my rather too extensive experience of these little motors lay odds on the fact that the motor is most likely in dire need of a thorough top-end over-haul.... From handy How2's in my profle; see " HOW2: Top End Rebuild Honda CB125 (Benley Motor)

It's actually not as major a mechanical melodrama as it looks, BUT it is the likely 'conclusion' to your pokings and proddings, ad IS likely to be a couple of hundred quid job, when you have got all the bts and tools to DIY.... if you try farming this out to a paid for mechanic, then, sorry, but the bike, as is is most likely beyond economical repair; you'd be better off punting to back on as is, to cut your losses, and sticking cash into something newer and more ride-away ready..... you have been warned.... make sure you are prepared for this before you start poking and prodding and hoping for the best... in ALL likelihood, all you will achieve is a lot of frustration of a bike that never does anything but play up, one way or another, waste a lot of time NOT making it much f any better, and spending a lot of money to avoid grasping the asty nettle along the way......

These bikes have TINY twin cylinder engines; each cylnder is barely the size of a mopeds, and expected to make twice the power a moped does.. not that it adds up to much at the end, a mere 10bhp in the case of the single carb benly engine... but t IS 'smooth'.... However; it has tiny pistons, a mere 43mm in diameter, with very very 'fine' piston rings, sittng in very narrow and very th grooves in the piston, ad those rngs have to be 'sharp' to hold compression and let the engine run right... they will wear out and cause poor running long before you observe significant cylinder wear, but that too wont help, nor will long periods of being laid-up, when the iron piston rings corrode in the alloy grooves and start to 'stick', and corrosion and crud n the oil gumms u the 'coil control rings' that spray oil on the cylinder wall and scrap t back off to keep the piston lubed..... IE they do NOT like being left to rust!

And comment that the seller said he changed the oil, but ts still black and tar like, doesn't bode well... Gven they take barely 1/2 a litre of cheapo oil, I wouldn't doubt that it has been changed recently... but see handy-how2's ad cleaning the oil strainer.. I doubt that has ever been done, and between old crud not flushed out with oil oil left settling for however many years, and some new use, with fire getting past knackered rings... yup, that would turn it tarry black pretty quick So I would not have too many hopes of avoiding a top end rebuild, TBH....!

IF IT WAS MINE..... first up would shelve any ambitions of riding it in much of a hurry... not that the Benly's like to hurry much to start with.... quick, they are not... a good CG125 push-rod single makes as much power and is lighter, and just as eager..... Benly is err... slow ad steady! like I said, its smooth and comfy, but 'spritely' it aint!... but I detract... were it mine, and plenty of good reasons it isnt' even though this does seem to be the place Little Honda Twins come to, like Lauds, in the hope of drinking from the fountain of youth, and re-living thier teen-dreams again.....were it mine!

1/ I would put any ambitions of ring in, i the immediate future out of my mind. Rushing be fast way to hurt when it comes to two wheels, and little different i the mechaics of'em.

2/ I would put little or no store in seller's claims or the worth of a fresh MOT cert... and I would start from scratch, givng t a thorough renovaton.....

See links in Profile I have done a few over the years, though most lately, and as far as Benly twins concerned on the slightly more spritely 125 Super-Dreams, that share the same basic engine

A-N-D the engine would not be the first thing I tackled..... Before you go, make sure you can stop! Then steer! Top of my list of priorties would be to check ad overhaul the brakes; these are, on the earlier Benly's quite nice cable operated drums, and as they use the same siz shes frot and rear, I would have the wheels off, and look for the old bodge of simply swapping shoes around to even out wear, and tightening the cable up, possibly even shimming the shes with old bake-bean tin to get a bit of extra bite..... Iroically, ew shes ad ew cable are remarkeably 'cheap' and not oo hard to 'do'... but before I spent that money, I would pull the tyres off, and check the state of the steel wheel rims and spokes.... steel rimmed wire spoke wheels rot from the side, and an MOT inspector cant look in there! It's also a diffcult or expensive job to rebuild wheels; new spokes and new rims are probably cheaper than tyres... which also beg attension... these thngs usally get pretty cruddy 'budget' ruber, that never wears out, but also seldom offers much grip.. even when new... and again, all the MOT man s concerned wth is whether there is legal tread depth or 'obvious' damage... crap old tyres can easily get through an MOT..... So those would be early targets on my to look at list, and long before the 'engine'..... especially as problems there can much more rapidly mount costs and make project even more BER.

Woking up from the floor, then, suspension and steerng would be next on the hit-list, and the head-race bearings would (again, see handy How2's!!) come n for scruitny. Bikes left drelct rust, and moisture in the steering arings collects around the balls, and rusts in 'pts' where they sit..... should make the steerig 'notchy' and MOT man should fail it...but very easy to drop the yokes, clean p the bearng racs with a bit of wet ad dry to smooth the pits a bit and fit new balls, to make it smooth eough to satisfy MOT man.... for the 20min of test.... after that, wear sees the bearing slack off, and the pits retrn, and steering likely horrble and fail the next MOT.... Modern 'taper roller bearings' are about £30 and I tend to ft them as a matter of course these days, rather than eff about with loose balls.... that, IF you replace the races, which s the problem part, is a bit, but not much cheaper...

Forks would the get stripped, stachions checked, and again, early Benleys had shrouds to 'hide' the bits that wear/rust, later ones usually given rubber gaters to do the same..... MOT man can't lift them, all he can do is check theres no oil leaks and there is 'some' damping effect.... So, I would strip and inspect the forks; and if the fork stanchons 'shot', like the wheel-rims, bike's probably BER and not worth wasting money on anything else... if not, new seals, new fork oil, careful rebuild... front end should be 'good'.

Back suspension is simple on a benly, ts a twinshock. It has two hinges on the swing-arm and two pogo-stick things either side. The shock-absorbers were ever great to start with; but the swing-arms do rot and the bushes do wear, ESPECIALLY on a bike that has been left to rust, and then pressed back into use with minimal attestation...... This would all get some attension and inspecton and f o more, strip clean and grease... but good bet new shock-absorbers would be very very worth-while.

That running gear, looked at, THEN, I might start looking at the fancy bits.... not that I would be in a hurry to 'pretty it up'... but the petrol tank is where engine work starts.... ad they again rot fro the inside, and again, as a matter of course, I gve them a POR15 lining treatment, as a precaution against so many presumed 'carb issues' where they such sludge flaking off the inside of the petrol tank! That would beg I look at the outside of the tank, and whether I would want to strip it to bare metal, and possibly patch any p-holes before lining and re-paintng, begging matchig to the side-panels ad other painted bits....

Handle-bar, switch gear, controls, and wirng, would all have to me messd with to do the headrace bearings and forks... so again, that would get some scrutiny.. early Benly's have loverly metal swtches and stuff, that can be wonderfully reconditioned with patience, sand-paper, and light oil... but is awkward and time-consumng... can make a bike a lot less trouble thogh... and beg followig through, going down the wires, looking at old corroded bullet conectors and conector blocks, cleaning making good and assemblug with lots of WD40.....

At that jucture I would probably also pay rather a lot of attesion to teh Starter solenoid... another wonderful bt of old fashoned engneering made with screws and bg bits of brass, that can likewise be stripped, cleaned, and reconditioned to aid potetial 'starting issues'...

These little engines have a 'self exited' ignition; that s they dont get sparks from the battery, they get sparks fro the magneto on the end of the crank; if they dont get spun up too fast by the battery, either 'cos that's a bit weak, or the solenoid is robbing volts, or the starter motor itself is rather tired, you will NOT get a decent spark, and all the 125 motors have a high compression ratio, so NEED a decent spark...

So, working down, after looking at the soleboid, I would pull, strip and recondition the starter motor; again, old fashoned screws and big chunks of metal, t is eminently reconditionable, and some elbos grase, LM grease and some new brushes (about £10 fro DSS_ will do wonders.... THEN I might worry about a ew battery... and I would not take seller's word about how good an unknown one may be for the sake of £20 and SO much potential frustrtion.....

Whlst in that vicinity, I would probably have many ideas to 'upgrade' the elevtrcs and fit better lights and 'stuff'' would try and rein in... make as good as standard before tryng to make etter tha standard.... BUT if it wasn't a 12v CDI system, I WOULD be sorely tempted to upgrade to that later standard, whilst I was faffing..... other than that, only 'mod' I would recomend is chucking away the old fashioned electro-mechanical indicator flasher, that has a habt of fllling with water and fitting a sold state electronic one....

That would beg I start prodding and poing indicators, cleaning contacts, replacing seals, and looking atthe headlap and teh spaghett situation in there....

THEN..... after pondering gitio swtch and petrol cap 'sets' to finish off those detaol jobs.... I MIGHT be ready to start looking at the motor.....

And as said, were it me, wouldn't look too hard.... I would like as not cut to the chase, haul the engine out, pull the head and barels off it, and do full top end rebuild, with a £120 barell kit of e-bay... new cylinders, new pistons, new rigs.... and as part of fitting, would beg that the cam-haft be accurately timed in, and the tappets correctly set, and whilst I was in there, I'd almost certainly strip the head, clean and lap the valves, to the seats, and replace the stem-seals.

So rebuilt, likely that engie would start, run and deliver it's all, and ot give a heart-beat's trouble there-after, for the sake of puttng i the time, effort and moey upfront for graspng the nettle..... provided I pay some attension to the exhausts and exhaust gaskets when put back n the frame......

A-N-D... I could take a bike from a derelict or scrub-up, like that, and do all that, ad probably have the thing up ad running and running very sweetly, in ooooh.... maybe a month? IF I was really keen.. more likely two, proably three,,, but realistically.... six-month to a year to almost never... (I have 'done' three, and have two work in progress, from the last seven years, in which my 750, 'err nibs 750 and the yellow one, all vied for Project D'Jour, honours!)

WHICH is back to that warning....... how optimist / naively hopeful are you?

IF you don't want to grasp that nettle... you can spend an awful lot of time poking and prodding and meddling i the margins, getting into a confusion of conflicting symptoms, never really storting ANY.....

Without grasping the nettle; hoping for the best, first thing I would do s pt a compression tester on the thing..... I have a pretty sophistcated one, that has all the adaptors I need to work on these little engine's with thier tiny cylinder heads and spark-plugs..... as they have a tiny 62cc cylinder, and a 6cc combuston chamber though, it's still not all that accurate, a push-in type car compression tester leaving the volume of the spark-plug threads, to add to the tiny combustion chamber, will tend to make a mockery of any reading you get from such a device... you'd be as well off using the old rule of 'thumb'... can you hold your thumb over the hole whilst you crank!

But, I would want some sort of confidence that the motor had healthy compression... as it stands I don't.... ad cost of buying tool to find out or paying some-one to tell me that bad news... I'd be 1/3 the way to buying a new barel kt and making the question redundant!

Whilst I had the plugs out, I would be comparg them to the pictures in the Haynes manual; fro described symptoms, of motor starting then cutting out, I would not be at all suprised if they weren't sooting up, either from too much choke being used, or ore likely burning oil....

Black shitty plgs and little compression, I probably wouldn't even other more poking... I'd be on e-bay looking for a barel kit..... but to percevere....

With some compression and a not too bad plug.... These little motors like to e spun up well to get going, and stay goig... it starts, which is a start, ad doesn't say that the battery/solenoid/starter are immediate issues... but as above they dont help if they are at all lazy..... So assuming they aren't too bad for now...

Basic service procedures of tappet adjustment and cam-chain tensioner adjustment are oft neglected, ignored or just plai cocked u on these bikes.... back to the handy-how2's... follow instructions there and the Haynes, and gve yourself the best chance of it all working as it should...

I would lookat the carb.... the floats on the do have a tendancy to stck, and fiddle fingers have a habit of screwing up teh settings.... they work wonderfully at the 'book'recmendations, though... so I'd stck the needle height back to that, I'd set the pilot air screw bak to that and then wind out the idle screw, and use the throttle to try ad keep it alive and find a settg where it will 'idle' and ot conk out... all when warm enough it dot need 'choke'..... good gayme... good gayme....

They are also a single carb on a branch manifold, with a heat insuator block between the head and the manifold to top engine heat boling fuel in the carb..... This is often omited during re-assembly or is cracked, or not sealing with new gaskets where needed or piched 'O-rngs either on the manifold or carb......

Carb would probably come apart in my hands, and be treated to new needle, new float needle, new jets, new pilot air screw and new gaskets, as well as thorough clean, to make good in this area... when I cant get it to 'idle' and stay alive......

Not that t would make much difference, and have me scratchig my head over the state of exhausts and exhaust gaskets... and back up the pipes at the fel pipe, ditch any after-market 'in-line' fuel filter, looking at the fuel tap, and the straier on the top, in the tak, and pondering that POR15 liner treatments......

And goig around the loop, probably lookig for other falorn hope 'problems' to avoid the nettle and a top end rebuild, and probably wastig more time and ffort and possibly money too, in the doing......

Which is why I cut to the chase and do Top-End rebuilds 'as course', same as lining petrol tanks!!!

BUT.... that's your call... like I said, I SUSPECT that this is no cheap and easy two minute fix, twiddling a screw or swapping a filter..... you might get some iprovement f you fiddle in the rght places, but big risk that fiddling wll make more problems than it solves, and the long and the short of it will come back to biting the bullet and doing that full top-end rebuld.....

And, Have't mentioned, IF it s an earlier 6v poits system.... then sparks can drop ot as they get warm when old condesners start to get warm and workig 'randomly'.... IF its a ponts ignition model, then as course I would replace both points AND the condenser as imediete precaution against ignition anomolies......

But otherwise; sticking your finger n the wind, and asking for suggestions.... there are possibly hundreds..... BUT.... my experience with these little motors, and I have rebuilt half a dozen of the chuffing things i recent years... do yourself a favour, ct to the chase, do a top ed rebuild, and make the motor as good as you can, before you start meddling round the margins.... but before you do THAT... make sure that the rest of the thing is worth ANY time and attension at all.... they are ot and will never be very valuable bikes, and what it's likely to cost to make one 'good' ad even notioally everyday reliably rideable, will be chasig the sort of money you can go buy a five or six year old, if ot newer YBR125, with just as much performance, and likely a lot less problems, if not so much 'charecter'.... or character building 'frustration'... So think LONG and hard about advice at the top, before you go much further, IF this bike is worth the effort...

There aren'tmany folk aroud as daft as I am... you MAY be in that minority, and find it all 'fun'... if so welcome to the club... there's no hope for you, seek psyciatric assistance at the earliest oportunity!!!! Otherwise... go see how 'cheap' good, road-worthy, runig YBR's may be procured for these days.... And see Snowie's Pup-Block of our marathon 'good as new' renovation of her 125 Super-Dream that cost as much or ore than a brand new YBR....... UNLESS you actually enjoy getting your hands dirty and playing spaners, this bike, I'm sorry to say, here ad ow, is likely to prove much more trouble than it'll ever be worth, either in cold hard £'s on the open market, or the functional value of riding the thing for the few miles it lets you for all the time, money and effort you invest it.....
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Rogerborg]

Mea culpa.

I'm so, so sorry.
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Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[Nobby the Bastard]

[nazK]

[Rogerborg]

[WD Forte]

The CB125T in Tefs link has more or less the same engine as your CD125
Whether it needs a top end rebuild though..................
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bikers smell of wee

[jaffa90]

[Teflon-Mike]

[redeem ouzzer]

^^ Teff'd
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Be a REAL MAN!

[Rogerborg]

[nazK]

@Teff Thanks mate, I am going to waste time, money and energy on it. I will learn something new and not to forget make friends here on the forum or to least get some banter out of it which has already started

I will need a lot of help from you and other senior members when it becomes a project after I get it pass this start/stay on issue to some degree

I bought the bike because I like it and yeah I could have bought a newer or Chinese bike but where is the fun or character in that..

every man has his tipping point, mine will be tested by her:)

@All: A friend of mine is going to lend me the charger, ordered manual on ebay and looking to buy owner's toolkit..

the battery seems a bit alive this morning after it went flat and gave relay ticking noise yesterday. Didn't know they are self charged while idle Back to square one, tried again which I should not have but could not help, it turned over but did not stay on same like when i first tried when delivered...

Now will not touch it until battery is charged and have the manual on me.
____________________
NEW TO BIKE MAINTENANCE- HAVE CD125 BENLY

[nazK]

Budget £20:

Are these the right options
https://www.ebay.co.uk/itm/Oxford-Oximiser-900-Anniversary-Edition-12v-Motorcycle-Trickle-Battery-Charger-/201901764148?hash=item2f02486e34:g:JboAAOSw5UZY-8a2

OR

https://www.ebay.co.uk/itm/Oxford-Oximiser-900-Anniversary-Edition-12v-Motorcycle-Trickle-Battery-Charger-/201901764148?hash=item2f02486e34:g:JboAAOSw5UZY-8a2

OR

https://www.screwfix.com/p/streetwize-swbcg6-6a-automatic-battery-charger-12v/7752r

OR

https://www.argos.co.uk/product/3803228?cmpid=GS001&_$ja=tsid:59156|cid:189934405|agid:18074225845|tid:aud-144400486596:pla-147157279285|crid:77627770765|nw:g|rnd:10402194144023937146|dvc:c|adp:1o1&gclid=CjwKEAjwlpbIBRCx4eT8l9W26igSJAAuQ_HGGAEJdl5oQtpbH4APcp-b-lpR-9rsJbg-Knq6FphBMxoC0J_w_wcB
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NEW TO BIKE MAINTENANCE- HAVE CD125 BENLY