This is NOT a definitive guide, nor is it a substitute for the PROPER Haynes / Clymar manual for the bike in question. Bike in question is a 1986 Honda CB125TD-C, in particular our 'Little Dream Number 7', but principle pretty much of a much for most bikes....
First of all you need to remove everything around the head-stock so you can get at the bearings. Main things will be the petrol tank and the head-lamp. If you have a full-fearing this probably needs to come off too.
I'm part way through a full-tear-down, so in this case most of everything had come off, including the engine. If you are JUST doing the head-races, though, BEFORE you tear EVERYTHING off the front end, there ARE a couple of 'cheats'.
Most of the wiring collects in the head-lamp, and on many bikes the head-lamp is attached to teh forks on brackets. To Save trying to undo EVERYTHING, the next stage is to drop the forks out of the yokes. When you do THAT if the head-lamp is on brackets on the fork tubes, you CAN often leave the head-lamp, with indicators and everything in one chunk, and slimply let it 'hang' off the wiring. You then have to work around it, but that can be easier than taking it all apart.
Next 'tip' front brake callipers are on the forks, and if you have twin discs there's often a splitter on the bottom yoke. Again, save disturbing the hydraulics, remove callipers from fork sliders, splitter if applicable from yoke, and brake lever assembly from handle-bar.
Then when you drop the forks you should be able to lift the brakes as an assembly off the bike. Handle-bars again, will probably have to come off. If they are clip-ons they'll be clamped to the fork tubes either above or below the top-yoke, so they'll need to be undone to drop the forks.
Conventional bars are bolted to the top-yoke, and they often cover the top-yoke nut which you'll need access to, demanding their removal. IF you are careful, again, you can lift them off as an assembly, without disturbing grips and switches, and hang them away from the head-stock.
That will about get you to THIS stage. Note I have a bike-jack supporting the front of the bike, as the forks aren't there to do it any more. How YOU choose to hold it up is up to you, blocks of wood, breeze blocks, little brother, your call.
Course it is easier if you have a 'proper' motorbike with .jpgnd31 If you have one of these posey things with only a kick-stand, you'll have to prop up the back end vertical too! (Tip: Car Axle Stands under the Swing arm often work well!)
Shown sat next to the top yoke nut is a 29mm Facom socket. This is rather larger than the sizes MOST socket sets go up to. BUT the sort of size most top-yoke nuts are. Shown, because you OUGHT to go buy one. Actually, check your top-yoke nut is 29mm first. If not buy a big socket that's the right size for what you got! (If it's not a Honda CB125TD!)
THIS is one of TWO 'specialist' tool you should need for the job, and you should be able to get an individual socket the right size from any good motor-factors for about a fiver. Even if you have to go to Halfrauds, shouldn't cost you more than a tenner, and it WONT chew the nut up like a pair of mole grips, a pipe wrench or a hammer and chisel will!
Provided of course the last monkey to look at these things hasn't already used such implements and make it like something that's gone through a meat grinder!
ANYWAY, if your nut aint chewed, great, but probably an indication as to why you are having to replace the bearings! These things DO need periodic maintenance. They need a bit of grease and a 'tweak' on the bearing cap to take up the clearance to stop them slopping about and knocking.
So if the nut AINT chewed, either the bikes had VERY diligent franchise stealer servicing, or more likely, the head-stock bearings have NEVER been adjusted... hence the slop & knock, hence the need to renew them!
But that socket I recommend you buy, well, it'll have paid for itself in the work-shop costs your not paying already, but it WILL come in handy when, in a few hundred miles, you open this lot up again to check the clearance as the bearings bed-in, and add a little grease.
Take note; THIS WILL NEED DOING. after you have fitted new head-race bearings. Like 'running in' a new bike, the first couple of hundred miles you do will see the bearing wear off any high spots in the rollers or races, and bash the races tightly against their seats, which will open up the clearances a little, quite soon. But after that, they should stay in tolerance for hundreds of miles or so, depending on use & type etc, and 'normal' service schedule can be followed.
ANYWAY, back to the plot.
Undo nut, lift off top-yoke. Underneath is the head-race thrust nut, & introducing the OTHER 'Specialist-Tool' you'll need for the job, a C-Spanner.
This is the 'correct' tool for doing/undoing slotted ring nuts. You know the ones that just have four notches n them not a hex, that you probably tackle with the faithful mole-grips, pipe-wrench or hammer & chisel, to randomly deform the things!
In this case the one I found fitted best came from Alf-Hagon with a pair of shock-absorbers to adjust the pre-load. But hey, it fits! You may be lucky and there will be one in your bikes tool-kit if you still have it, again for adjusting the shock pre-load, of again they can be bought reasonably cheaply from good motor factors or bike 'places'. I think Machine Mart do a set of three for about a tenner. Again, even buying a set, your quids in against paying a mechanic, and have them for when you come to do routine maintenance.
PLEASE, do NOT have the idea, "Ah! THAT'S what the curvie bit on the back of my bicycle spanners is!.... I'll Try THAT" Well, you CAN, its a free (ish) country.... but I only advise it if you REALLY like seeing blood drip from your knuckles! I KNOW I learned that one the hard way too!
Oh yes, and the more observant of you WILL have noticed I have the spanner in the do-e-up position.... sorry, forgot to take photo taking it off, so have subbed the one putting it back on.... same deal, just turn the spanner upside down and tug the opposite way.
At this point, you'll notice I have my knee against the bottom yoke, holding it up, having taken the bearing nut off, and am lifting off the upper bearing race. And I'm holding an old car speaker in my spare hand.
This is to catch all the balls from the lower race! when you undo the nut, the bottom yoke will have nothing holding it up, gravity will take effect, and it will fall, letting all the little balls follow it!
In this case, I'm not to bothered about loosing them, because new taper-rollers are going in, in their place, but they are a pain to pick up once they have scattered. So I use the magnet to try and catch them all, if they try escaping!
Once your balls have dropped, you can withdraw the bottom yoke and stem, and turn your attention to drifting the races out of the head-stock and off the stem.
SORRY! I apologise, I have just realised I am about to introduce two more tools many might consider 'specialist; items! The first is a tyre iron, the second is a selection of engineers chisels and drifts! (Usual caveat; good motor-factors under a tenner etc!)
Photo, above, using tyre iron to lever the bottom race off the stem. You'll probably need to remove the head-stock seal first, and that will give you a 'groove' to get the lever into.
Trick, if there is one, is to apply a little gentle pressure on whatever bit of the rim you can get in on, then go to the opposite side, and apply an equal amount of persuasion, then come back and do a bit more close to where you were to start with, so with each push, you are working around the race, lifting it as 'square' to the stem as possible. Lift it too much on one side in one go, and it will jam on the shaft.
After a few goes though it will start moving, and as the gap gets bigger you may need to put a bit of packing under the fulcrum, / pivot point of your lever to get a decent purchase on it, but with not a LOT of effort and a little perseverance it SHOULD just 'pop' off.
Now you can do the head-stock races, and these are a LOT more satisfying! BIG hammer and something long and hard! as your drift. I used an old rocker-shaft from a Rover V8!
Get inside the head-stock through the upper race to find the rim of the lower one, give it a smack! Then give it another on the opposite side, then move round a quarter, and do the opposite to it, and repeat until it comes out. Should only take a few smacks! Then you can repeat from underneath to do the upper race. MIGHT be helpful if its a light bike to have some-one hold the frame down while you do this, but DON'T let them peer over the head-stock to see what you are doing!
Well, you CAN, depends how much you like them I suppose! They'll end up with a hardened steel ring in their forehead, that's all! If you like them, stick a rag over the top to catch & damp the race as it comes out!
OK, that's the assembly stripped. If its old, you might like to spend a bit of time cleaning it all up at this point before putting it all back together again. Paint is your preference.
So, bottom yoke and stem, cleaned and in this case painted, time to drift on the lower race bearing. There SHOULD be a seal beneath it, so take note what comes out when you remove the old bearings and check how the new seal fits.
On this bike, the taper-race kit that comes from Dave-Silver-Spares has a seal-washer that has to be fitted BEFORE the bearing is drifted home. Here though I am using a bearing kit off e-bay that didn't have a seal with it so am using a rubber O-Ring that can be fitted over the bearing race AFTER the bearing has been drifted home.
Also, pay attention to the bearings in your kit. On most bikes the lower bearing race will have a larger internal diameter to the top bearing, and the bottom of the stem will be slightly larger than the top.
Top bearing is also a sliding fit on the stem so that you can tighten it down into the races to take up wear. Lower race is an 'interference' fit, or effof tight and CAN take some wamping to drive it onto its seat. Get the bearings the wrong way round, though and you can spend an ETERNITY hammering the upper bearing onto the lower position on the stem.... and then have a VERY loose upper!
ANYWAY, I used a soft faced engineers chisel to tap the bearing onto the stem, as ever working around the race on opposites, and you HAVE to be EFFOF careful to ONLY hit the rim of the race NOT the rollers or the cage they sit in.... or you wreck the bearing!
Next job, tapping in the lower race. AGAIN carefully, getting it into the head-stock 'square' and ONLY tapping the rim of the race NOT the bearing surface where the rollers roll
Having tapped it in 'gently' flush to the head-stock tube with the flat of the hammer, it needs to go a bit further to 'seat' and leave room for the seal. So to tap it the last bit of the way, I use an engineers chisel again, AGAIN only on the rim, and working evenly around the rim to keep it square.
As you tap, the note the hammer makes will change from a ringing to a dull thud, once the race has gone 'home' and is seated on its step inside the head-stock.
The upper race can be done in the same way, but from above, and that MAY not have to sit so low in the head-stock, it might sit flush with the top, depending on design, because it doesn't have to accommodate the seal beneath.
Both Head-Stock races drifted home, you can take the bottom yoke and stem, and loose assemble it, and grease the rollers. Liberally smeared with grease to be sure that they stay lubricated, I use Graphite grease, rather than general purpose or LM grease, but it shouldn't matter TOO much which you prefer.
REMEMBER the BOTTOM SEAL!
With the upper race lifted off, you can push the stem up through the head-stock and seat the bottom rollers in the race, drop the upper rollers into their race, and hold all in place while you add the thrust washer, if there is one, and then the bearing nut.
And Back to the C-Spanner to tighten. "How Tight?" Well, that's a good one. rule of thumb is to tighten the bearing up until its stiff to turn the yokes, then back off about half a turn or until the steering feels smooth, but without there being any play in the assembly.
TIP: As you tighten the bearing nut, WAGGLE the lower yoke left and right, to keep the rollers rolling. This A) helps you feel how tight they are in the bearing, and b) stops you 'flatting' the rollers by over tightening them in one position.
Reason for 'over-tightening' the race and then backing off, is to make sure that you HAVE drifted everything 'HOME' and the tightness you are putting on the bearing IS 'pre-load' and not pulling the cups into the head-stock or dragging the stem up through the lower race.
All tightened up, you can replace the upper-yoke, and the top nut, with that nice shiny new socket you bought, stand back and admire your handy-work!
As far as I'm concerned, JOB DONE. I have the rest of the bike to work-over and do swing arm bearings and the like, and I have to fit new fork-seals before THEY can go back on. But if this is the entirety of your task, you merely have to re-assemble as the reverse of disassembly to get to where we started, to be finished.
Ie: Line up the head-lamp assembly, slide the forks back in, re-fit the brakes, tighten everything up, put tank on, go for a ride!
For a novice mechanic, job should take about half a day on a typical street-bike. I'm doing THIS bike as 'Monkey-See-Monkey Do', to show the G/F how to do HER bike, and little thing she is, didn't struggle with anything except levering the lower race off the stem, so SHOULDN'T pose much of a challenge to any-one with half an ounce of common sense and the ability to read this and the work-shop manual!
Bearings are about £20ish on e-bay, £30ish from mail-order suppliers, whatever they can get away with from main stealers!
Independent Mechanic would charge about £70-90 for this job, depending on the bike, so you stand to save yourself about £50 by going DIY. So its well worth the doing, and as said, worth acquiring at LEAST the socket & C-Spanner so you can adjust the bearings again as routine maintenance, and DO remember that they WILL need a 'bedding in' adjustment after a hundred miles or so, to take up the early wear slack. Basically repeating the bit where you waggle the head-stock and tighten the nut over the top, and for THAT, as you don't have to remove the Yokes, you shouldn't have to drop the forks or hang the head-lamp.