Honda cb250 nighthawk issue

[Burgemeister]

Hello everyone

I have a Honda cb250 which I got to try and turn into a tracker scrambler type hybrid of that makes sense. I like the cafe racer look but equally like the chunky tires and higher exhaust look.

After I bought it (as a non runner) I put some fuel in and changed the spark plugs aswell as putting in some fresh oil.

I changed the battery as the original battery Wasnt holding charge.

The bike then started although very groggy and kept cutting out at least I knew it had the potential to run. It went through all the gears and the brakes did work although could do with some new pads and tyres.

So I then made the rookie error of washing the bike with a hose and then low and behold a few days later I couldn’t get the bike to start 😔

I have opened the run switch and ensured it was dry

I have made sure the battery terminals are all tight and all fuses seem okay

I have replaced the starter solenoid (I think) the first box which the neutral and live bolts into from the battery.

I have changed both the ignitional Coils

I am now lost for what to do!!!!!!

All lights and signals work, the starter motor spins but I don’t seem to get any chugging from the engine.

Could anyone give me any insights into what could be wrong?

Could it be starter motor?

Should I replace the run engine switch?

It’s tacking my brains now so any help would be fantastic

*** I also live in the midlands so if someone can add me to that group I would appreciate it ***

Many Thanks

Dave

[Easy-X]

Sigh... the standard check list:

Are you getting a spark?

Do you have compression?

Are you getting fuel?
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Burgemeister]

[Teflon-Mike]

For clarity: when you press the starter button, you get no chugging or whirring, indicating that starter not turning over? Yeah?

Starter solenoid on these should be as per the CB126 Super-Dream. Big round metal thing with four contacts on the top. Its not live and neutrral... its not a three pin plug! Its the 'supply' from battery + and the 'feed' through the solenoid to the starter motor. Inside is an electro-magnet and a big brass plate. Two wires, one +ve from the starter button puts volts on the electro-mangnet, other is the earth for the electro-magnet; when they have volts accross themn, the electro-magnet shifts the brass plate 1/2" or so over two contacts, to make the circuit from the battery + to the starter-motor.

The solenoid has a habit of filling with water.

Conveniently its an old fashioned thing, that, if I remember right is screwed and crimped together, and is eminently DIY take-apart-able. If you do so, you can a) file the contractor plate and the contacts it touches to remove the lilely corrosion and pitting; b) flood the solenoid housing with WD40 to, curiousely enough do what the bludy stuff is designed for! "Water-Dispersant Formula 40" fact it offers a little lubrication for the electro-magnet core is a convenient side effect! But work it back and forth a bit to free up and make suire it is clear. And solenoid should be 'good' when you put it back together.

Next up!

Starter motor; has carbon brushes in it that slide on the commutator and feed the volts to the winding in the motor. They wear out. As they do so, they leave a dust of carbon over the commutator, and that can 'short circuit' the contacts so that two or more windings try sucking electric from the battery at the same time, rather than just one or three, and rather than making magnet to 'help' spin the starter motor over, they make magnet that tries to slow it down. Add some pitting on the comutator, and some lack of contact area from the bruah wear, and lack of spring pressure as they get shorter.... starter motor starts to get lazy, as well as suck more amps.... which in tern, puts ecttra load on the solenoid to help that pit and furr up, and on the battery to help that loose charge holding capacity.

SO....

You dont just tackle the symptom, and swap the battery, 'cos underlying issies will likely just kill that in double time.

You pull the starter, and recondition with new brushes.. and you pull the solenoid, and recondition with a flat-file.. tedius and time consuming, but only around a £20 job in total, mostly for the new starter brushes.

When starter-motor 'done' you pay very good attension to the fut. It finds its 'earth' through the bosses where the motor touches the engine; so you use that flat file again, to make sure that there is good metal to metal contact between the two.

There should also be a good earth between the engine and the frame back to the battery -ve... bad bolts and old rust usually mean there isn't; so again, more fettling and cleaning may be required, BUT, neat little mod here, is to make an auxiliary earth straight from the starter-motor mounting bolt, back to the battery negative terminal.... a bit of 3A wire, will NOT really cut it.... an actual earth-braid from Halfords for a car, is quite good, if not, something made from an old jump-lead will do, b-u-t, again, the thing is going to be expected to carry perhaps 50Amps or more, crimpy ring connectors are NOT really going to cut it! Propper high-amp terminals will be required, and good contacts between them and wires needed.

But, good starter, good solenoid, and you aught be good to go... BUT, personally, when test sarting and fault-finding I do NOT try start from the poor little bike battery, but use a walloping big old land-rover battery and jump-leads to give the sustained amps that the starter motor sucks, without either flatting the battery so fast, or killing it, boiling the electrolyte trying.

But, you need to make good the starter system, first.

THEN we can start pondering coils and CDI's and stuff!

Add on edd: if starter motor wirring, but engine not chugging... above still not off the menu. Likely problem is that the starter 'clutch' is sticking, if strarter motor wirrs. Means pulling the generator cover, and cleaning the one-way-roller on the back of the rotort, which aught beg pulling the genny rotor... BUT, pulling starter to overhail, begs dropping the starter chain, which begs taking that cover off and having a poke, anyway, and with a 'bit' of judiciouse back and forth and some penetrating oil... note penatrating oil NOT WD40, they 'can' free off a bit to savce pulling the genny-rotor which can be a bit of a bast... hence likely needed cos never done! But again, if it comes to that, you pul the rotor, clean the rollors, clean the ramps, re-assemble with good grease, and they should be 'good' for a while... BUT.... tired starter and tired soilenoid will still mean lazy starting and kill batteies in quick-time.
____________________
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?'

[Robby]

Drain the carbs into a cup. See if there is any water in the fuel.

[Burgemeister]

[Burgemeister]

[Teflon-Mike]

[Burgemeister]

Here’s a pic of what I found ...

[Burgemeister]

How do I add pictures 🤷🏻‍♂️

[Teflon-Mike]

[jaffa90]

Pics, in post reply i left click (add attachment) then (choose file) in your pics select a pic and left click pic and submit.

[Burgemeister]

[Burgemeister]

[Teflon-Mike]

Pic 1 is your generator cover
Pic 2; looks clean in there. That's the rotor that is usually a swine to pull, but of you have the Haynes and I think its an M20 bolt (RTFM for exact threead!) It might, if its botr so sotted up in there pop of a treat.
Behind it, where the chgain, which looks pretty tidy is, is a sprocket that turns on a one-way roller.
Again RTFM I think theres a picture of it. There's three rollers between the sprocket and the crank-shaft, and the rollers are 'loose' and when the starter togs the chain and turns the sprocket, they run up ramps, and then start turning the crank-shaft. When the crank-shaft starts spinning faster than the sprocket, they run back down the ramps and the sprocket free-wheels on the shaft.
These rollers must be 'stuck'... usually from rust and gunk that doesn't seem so obviouse in your genny case, but still. But the one-way rollers must be stuck in the 'off' possition, or the motor would turn with the starter, and the starter would be being driven by the engine when started.
Needs pulling, stripping, cleanbing and lubing... should sort the job.
Pic 3... now you got a problem. That looks like the generator stato0r that 'should'be bolted into the genny cover.
Ends of the winding potting look a little aeor-chocolate... could just be the resin when set, could be somethig has been dragged round by the rotor, like a paper-clip or staple or something stiuck to the magnets.... but NOT a particularly worry-spome image...
Fact you have taken the dang thing out of the genny cover, though IS... now you have to get it back in, and properly lined up and indexed!
Could a knackered strator be a problem? Yes... but not one that would effect whether the starter-motor turned the engine over. That has to be the starter-motor, starter chain or starter clutch.
Rotor spins around stator and makes electric... if the stator kerblugered it ight not make electric to make sparks so engine starts, or it might not make electric to charge battery, so starter wont spin.. but if you have charged battery to turn starter-motor... no... it shouldn't really have any effect, that would explain current symptoms
____________________
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?'

[Burgemeister]

[Burgemeister]

[Courier265]

Holy shit! I don't like the sound of that..
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CBF500 - 2 x Inazuma 250

[Burgemeister]

[Bhud]

[Burgemeister]

Is that a difficult job to do, does everything go back in the same way? I don’t want to take on a task that may be too advanced

Thanks

[Bhud]

In general it's an easy job. You need to get yourself the Haynes manual for that specific bike. There will be some other issues you need to take care of on the bike that will also benefit from you having a print copy of the Haynes at hand. These manuals are written and proofread by engineers who reverse-engineered a working example. It will have instructions and photos on how to disassemble and reassemble it without making mistakes.

Just my opinion, but before doing anything else to that bike, I would take a look at that starter motor and sprag clutch, just to rule out the worst case scenario. That noise is awful, and it would stop me dead in my tracks and I wouldn't do anything until I'd figured out the cause.

For now, just sit back, buy the manual if you haven't already, and wait to see what Tef makes of that video.

[Teflon-Mike]

First vid trells me nothing.
Third vid... sounds like the starter clutch is struggling to engage/disengage... it needs stripping and lubing... yes, big round thing with magnets in is the rotor. RTFM!!!
Starter clutch is on the back of that, and yes, the chain between the little sprocket and the one on the crank behind the rotor will need to come off, and the small sprocket on the end of the starter wil likelyt come with it, as its not bolted on.
Second vid.... you have slow starter, even with a plug out the hole giving it less compression to work against.
See earlier post... you need good starter, good solenboid and good nattery, OR weak-link will kill new battery toot-sweet. Make sure battery good and fully charged before fault findi8ng, and see tip for using a car-battery for fault finding to avoid killing bike's likely new one.

SPARKS... weak and intermittent... this is not suprising; ignition is 'self exited' ie it makes electric for sparks only when the crank spins; it doesn't take electric from the reservoir of the battery to make sparks; SO, to get good sparks, the generator has to spin, and spin at running like revs to make a decent spark....

BTT go sort the starter, the solenoid and the battery, recon starter clutch... THEN, you might be able to tell whether the weak spark is still weak, pointing to 'something' in the ignition, like a duff HT lead or coil or CDi... though as you got spark that NOT so likely... and sorting starter so it spins as fast as it aught and makes electric it aught, it'll probably make sparks as it aught.

Fault-finding like this isn't magic or voodoo, just logic, and not prodding in the dark or guess-work; its just following the logic... which here, says sort the chuffing starter system, FIRST, cos that's at the top of the chain, and work your way down.

If it ran for a few seconds then conked... Hmmmm.... I would have pulled and inspected the plugs when it conked. I suspect that they were sooted up, hence didn't make sparks, hence conk. Sooting up, would either be too much choke, or flooding float-bowl, both likely, or oil getting past the piston-rings or down the valve guides... also and probably more likely, given that the valve stem-seals on these motors start to perish at about 10 years and be crumbly as an OXO cube by 20, whilst lay-up resustitation and gummed piston rings are a perenial, and these motors dont really like either worn bores or old piston-rings.

On the 125's, I plan a top-end rebuild, with new pistons, rings and barel, new stem-seals and lapped valves, pretty much as a matter of course, to save so much more faff fault-finding chit like this... It's no harder hob on the big-bore Benlys, and parts are just as cheap and available from Chinky-Land on the bay; budget around £100-150 ish for a barel kit and stem-seals. See handy-how 2's in profile for it done on a 25, which apart from having one smaller piston up whilst one is down, where you have two slightly bigger slugs both up opr both down, its the same engine! A Full top-end rebuild can be done, pretty much by a complete numpety. following instructions in the efin manual and my how2, COMFORTABLY in side a week-end. No majorly special tools required, though I'd advise a low-range torque wrench be procured, and the special tappst key and lock-nut wrench, bought. Those two are about £15, and you will need them for regular use, checking tappets clerances every other oil change, about 1000 miles apart, and to tension the manual cam-chain tensioner from time to time.

Diligence of doing a top end, doesn't tyake much, just the mind-gruntr of braving looking at oily bits; Following the instructions to put it back together, begs so many normal service procedires; like making sure tappet clerances are right, making sure cam chain tension is good (As well as cam-timing right) Ensures oil dont get past the rings, or down the guides, as well as ensures that valves actually open and close and seal properly when they do, and all 'aught' work right.... so any opther problem, 'aught' be some-where else, like the ignition... to which there is actually bugger all to go wrong.... (as long as you dont randomly remove stator windings and stuff!) CDis tend to make sparks or not, coiuld make sparks or not, HY leads make sparks or not.... and you have sparks... not good ones, so likely eliminates most of that side of stuff, leaving just the single slide carb.... which CAN be a bit of a PITA... especially if half a dozen numpty owners have all has the same idea that it needs 'cleaning' and that cleaning a carb is a lot less scary than looking at oily bits, like tappet clerances, and effed it up along the way, refitting withouut new gaskets, faffi9ng with the slide needle height and using squirty stuff rather than elbow grease and patients.... BUT... If you have eliminated all upstream likely problems... than properly overhauling the carb, using nice new gaskets, patience and elbow grease, and making sure that the choke actually works and doesn't stick on, and that the float valve isn;t stickiung ad the float-bowl flooding petrol over the main-jet.... or worse, out the vent-hole in the top of the carb-body, which is common... then SHOULD be good to go.... BUT the key is working logically and methodically, and eliminating problems from the top of the list.... like the risk that pligs are oiling up 'cos its burning oil from worn rings/bores and or crumbly as feck valve-stem-seals.
____________________
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?'

[Burgemeister]

Thankyou both and yes just ordered a Haynes manual 👍👍👍

Is the starter clutch the gear looking thing behind the Rotor?

So I take cover off

Use a spanner and socket to remove rotor.

Take off small sprocket and chain

Replace the big gear ⚙️

Put it all back?

I’ve seen a video where somebody tries it and bearing fall out is that the norm and do these need replacing!

Thanks

[Teflon-Mike]

Oh-Kay... the CD Two-Fifty is the exeption to prove the rule. CB's usually denoted a more 'sporty', twin-carb twin-cylinder engiine, the CD 'Benly' badge was given to more soft-tuned, single carb, twin cylinder engines. What you got is one of the big-bore 'Benly' engines, with a single carb... or at least it should be.

Off the Top of my Head, its the same Keihin PD26 slide carb used on teh CG125, but with alternative jets in it. Usefully there are plenty of cheap overhaul kits on the bay for CG125 engines, BUT, the jets and needle are often completely the wrong size, intended for a CG, and there are a LOT of different varients of the PD26 used on the CG, with later examples being 'pumper' carbs, with a secondary accelerator pump to squirt a bit of enrichement into the air-flow when you open the throttle a bit quick, cos the jets are down-sized for emmission borrox. All slightly irrelevent, other than to say Read-The-Fucking-Manual... make sure IF you get any bits they is the right ones!

FWIW, I use the cheapop chinky CG carb overhaul kits on the CB125's; I chuck MOST of what comes in them away, 'cos its completely useless.... BUT, the most niggly bit to get your mitts on is the porimary air-screw, that has a habbit, especially on long lay-up deralicts, of corroding in its driling, so that the fine needle on the end snaps off when you unscrew it. Other useful bits of the kit are the idle stop-scre, that is usually chewed to bludgery ad IF you are lucky the float0bowl gasket.... though often completely the wrong shape, cos manufacturing tooling so worn out! But, still usually cheaper and easier to get hands on than a single genuine idle air screw, and bits like that, and some-times the float valve needle are useful.

The 'Sprag-Clutch'... the CB Two-Fifty dont have one. A sprag-clutch is an idler gear in a gear-train, that sits slightly out of line to the train, and has it's spindle in a slot, rather than a hole; so that when the starter turns engine, the gear is pushed down into engagement to make crank spin; when the crank is spinning faster than the starter, the idler gear 'relaxes' in the slut, and disengages... it's rather like the ramps and rollers of the one-way roller I described you had on the back of the genny rotor, but a bit less plush and cheaper to make. Comon problem on many more modern bikes, BUT you dont need worry about it, you dont have one! What you got is a one-way roller.

And yes; its the three 'bearings' you saw fall out on the You-Tube tut!

No, you dont use a spanner to remove the rotor. You use a spanner to undo the rotor bolt, in the middle, THEN you screw I think its an M20 bolt into the boss, to 'press' the rotor off the crank. As said, RTFM for exact size and procedure.

If you undo the rotor bolt and start wacking and prying the rotor, to try get it off the crank-shaft, you will likely either put a hole in your crank-case, bugger the main bearing and or bend the crank-shaft.... like I said RTFM... it 'aught' to be dead easy if you follow the instructions and use the screw-pressure of the afore mentioned M20 bolt.

If not? Well, you can resort to trying a hub-puller for a car wheel-hub or that sort of thing.... but in my experience, if its that stuck, it AINT going to come off in a hurry, and all you are likely to do is set things up to hit you hard in the forehead! When I come across rotors THAT stuck on, I take the whole motor to my local friendly engine reconditioners, and let them stiuck it on a hydraulic press, like wot they stick new valve guides and hot-spots into bus cylinder heads with... it can exert a pressure of a few tons per square inch, and things tend to pop off at the sight of the bludy thing rather than making you sweat, or pull puller claws out your cranium! And my local work-shop will generally do one for a bit of beer money for one of the 'lads'.... who is probably now older than eye-iz, rather than a spotty sixteen year old aprentice... but that' another story.

But start with the Haynes manual, and the M20 bolt.... then worry about pro-work-shops.

Once the rotor is off, THEN you can look at the one-way-roller clutch behind; as said, its basically three parts; a centre that has three slots and ramps that the three rollers sit in, then the 'hub' that is in the starter sprocket that sit over them.

When chain tigs big sprocket, pulls rollers up the ramp, locks the hub. and turns the crank-shaft. When engine running, and crank turning faster than sprocket, rollers fall back down the ramp, and disengages drive.

If worn or rusted, the mechanism stiucks or jams and makes the sort of racket, or worse, heard in your vids.

Strip it. Clean it; Parafin and fine wet and dry; grease and re-assemble... job-jobbed.

Little-sprocket and chain? You will be there til;l doom-day trying to do that. again RTFM; you remove the starter motor first. As you pull that from its rebate in the back-plate the sprocket will slide off teh shaft... so get ready to catch. If you DONT remnove starter first; then you will be pulling ths small sprocket against the chain that holds in on, and you will either kerfucker the chain, or just never get the sprocket off, or both. As said, RTFM, starter comes outr first....

And advice at TOP was to pull that, so that you could recondition it with new burshes and grease, and clean up the mating faces to ensure giid earth path, aided possibly by an auxiliary earth strap.

PLEASE, RTFM and follow advice; stop looking for short-cuts. If you DONT sort the starter to negin with; if you dont recondition the solenoid, you will NOT save yourself any time or hassle, you will perpetually be coming back to the same old problems you thought you had sorted, as the fix dont last, and tired old starter labours, throuh tired old so0lenoid and KILLS nice new batteries, as you use the starter ever harder and ever longer, trying to crank clapped out old deralict, that never really works properly, and you have a jigsaw puzzle of whats what and what was and wot you done to it, all adding to the confusion.....

Hence, as said, on the 125's I cut to the chase and do a top end rebuild with new rings, pistons and barel, new valve stem-seals and relapped valves. Base lines the problems before you begin, and sorts oh-so-many of them before you start looking, let alone fretting over what might be right what might be wrong, and what you can do without looking at oily bits an the frightening sight of half an engine!

Be brave; bite the bullet; do it right, do it once!
____________________
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?'