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Home Repair And Restoration

CBF125 Fork Seal Change

Repair Date - 19 December 2016

By Ren Withnell

Dammit. At 59000 miles I shouldn't complain but the right hand, off side, brake side fork seal is leaking. I suppose I've had my money's worth out of it.

A new seal and dust cover costs £9.34 for genuine Honda items from Wemoto. You can get cheaper ones from Fleabay but for the price difference I thought I'd stick with genuine for once. 1 litre of fork oil 10 SAE weight as recommended by Haynes costs a further £8.70. It's hardly a disaster. 

Step 1 - remove the front wheel, front brake, and mudguard. Unclamp the handlebars and push them out of the way.

The front of the CBF with no front wheel and the brake calliper hanging freelyWheel of, mudgauard off, brake calliper removed.
The handlebars are unclamped and resting out of the way The 'bars can be rested out of the way.

Step 2 - undo the lower pinch bolt a little, enough to release the clamping force that's all. 

The pinch bolt on the bottom yokeJust loosen it, you don't need to remove the pinch bolt.

Step 3  - undo the nut that holds the top of the fork to the top plate. 

The top bolt that holds the stanchion to the top yokeYou will need to remove this bolt. Don't lose the washer.

Step 5 - only loosen the fork's top nut. This bugger will be tight. As you can see I've used my vice to hold the stanchion between 2 pieces of wood. Don't clamp the stanchion directly in the vice as the metal jaws will damage the quite delicate chrome plating. You'll need a large 27mm spanner and a firm tap from a hammer. If you don't have a vice you could reposition the stanchion back in the lower yoke and tighten the pinch bolt to hold everything tight. There's restricted access though so you may need to remove the fairing.

The fork held between 2 pieces of wood in the vice, complete with spanner and hammerUse wood! Don't damage the chrome as the metal beneath will rust and damage the new seal.

Step 6 - place a rag over the fork's top nut. Why? There's a bit of tension in the spring and when the nut comes out it can fly off hurting you or damaging the working area. A rag over the top makes catching and holding the nut a lot safer. Ask Stephen Latchford, he turned up at the club once with a hexagonal imprint in his forehead. A fork top nut flew off the bike into his skull, luckily no harm done save a hilarious war wound. 

A rag is placed over the nut before removal to protect the mechanic and the surroundingsBe careful as you undo the nut, it might shoot out at high speed.

Step 7 - prise out the dust seal and the seal retaining ring.

Prying out the dust seal with a sharp screwdriverThis is the easy bit.
The seal retaining spring is also easy to remove.And so is this. 

Step 8 - remove the tube, the washer and then the spring from within the stanchion. Make a very careful note of the order in which they came out!!

The top nut, the tube, the washer and the spring.They came out in THIS order...

Step 9 - drain the fork oil. 

The fork upside in a funnel allowing the fork oil to drainRemember to dispose of it in an environmental manner. 

Step 10 - Undo the 6mm socket bolt (allen bolt) from the bottom of the fork leg. Prey to the mechanical lords that the whole inside doesn't start to turn with the bolt. Handy tip, if this happens put some tension on the stanchion or spin the allen key as fast as you can. I've seen it done with drill before now.

The lower leg with the allen bolt ready to undoYou might want a little leverage on the allen key.

Step 11 - remove the fork stanchion. AGAIN!! Note the location of all the parts.

The internal parts of the fork leg in the correct orderThis is the correct order...well at least in my fork...

At this point a further note. Most fork legs won't come apart at this point. The slider bushes will jam into the fork seal. This is a good thing as you can use the stanchion's bushes as a slide hammer to hammer out the fork seal. It seems the CBF125 doesn't have bushes! As such the stanchion just slides right on out. This leaves the seal in place. According to Haynes you can simply prise out the old seal with a screwdriver or buy an expensive fork seal removal tool, a kind of sliding hammer. According to reality...

Step 12 - fight, jiggle, hammer and wrestle the old seal out. I used my Dremel to CAREFULLY cut into the metal ring of the seal. Then I delicately hammered the metal into submission. This does of course cause a little damage to the soft alloy of the fork leg.

The old seal with 2 cuts where the dremel has been usedI made two notches in the old seal wall, being careful not to cut into the alloy.
The old seal being cut, chiselled and heaved outAnd used a small chisel to break out the old seal.

Step 13 - remove the sharp edges caused by chiselling out the old bush. I used some emery cloth to de-burr and smooth out the chiselling marks. This of course fills the fork leg with grit, metal and dirt.

Step 14 - thoroughly wash out ALL the foreign bodies in the fork leg. If it is not totally clean the dirt and grit will mix with the new fork oil and act as a grinding paste, damaging the whole fork system. 

The rought and dirty seal seat that will need cleaningThis will need thorough cleaning and the metal needs to be smoothed out.

Step 15 - insert the new seal. I use a socket that's just a little smaller than the seal to carefully tap the seal down into place. Be patient, don't rush and try to keep the seal going down evenly.

tapping in the new seal with a big socketTap tap tap not whack whack whack.

Step 16 - replace the seal oil seal holding ring. Give it good clean too. I also smear it with grease to hold back corrosion.

Step 17 - start the rebuild. Note the part circled in red goes into the BOTTOM of the stanchion. The rest goes in via the top. First the damper (the small tube with the holes and the short spring). Then the long spring. Note - you'll need to remove the spring later it just helps with the next step.

The peculiar part goes in the bottom as shown, then the damper and spring
I don't know what this part is called but it goes in at the BOTTOM, the rest via the top.

Step 19 - when these are in place holding the stanchion horizontally to stop things falling out, reinsert the stanchion into the fork leg (the black alloy part). Refit the 6mm socket head (allen) bolt into the bottom of the fork leg. This screws into the damper rod. You'll have a battle to get the damper rod deep down into the bottom of the stanchion, located into the circled part and then lined up to receive the socket head (allen) bolt. Also note the socket head (allen) bolt has a small brass washer. This is to seal in the fork oil. If this is damaged you're going to have to replace it.

Step 20 - refill the stanchion with fork oil. 10 SAE weight is recommended. With the fork leg pushed right down and no long spring in situ the oil should be 167mm below the top of the fork stanchion. I used a regular tape measure as a dipstick, it's as simple as that. You'll want about 150ml of oil so a 1 litre bottle is more than enough. Be sure to slide the stanchion a few times to remove any trapped air.

Measuring the fork oil level using an ordinary tape measureSet the tape measure to 167mm...and dip.

Step 21 - replace the spring, then the washer, then the tube in the correct order.

Step 22 - replace the top nut. This requires pushing down on the spring while turning the nut until it has fully caught the threads a few turns. It's a fighter! Be patient and be careful not to cross thread the nut into the fine threads of the stanchion. Don't use a spanner until you're sure it's not cross threaded. If the rubber seal is damaged you'll need to replace this.

Pushing down on the nut against the spring is a fightGeeet in ya little bleeder! Patience and care.

Step 23 - tighten the top nut. Again use the vice and wood or the yoke's pinch bolt to clamp the leg. It needs to be tight but you don't need to give yourself a hernia. Secure rather than tight as #@!$

Step 24 - fit the new dust seal. Just a few soft tap-taps with a hammer will see if settle into place.

Step 25 - reinstall the fork leg. Again the pinch bolt needs to be tight but not aggressively so. Same with the top bolt. 

Step 26 - replace the mudguard and the front wheel. 

Addendum.

With 59,000 miles on the clock when I looked at the stanchion there was a small area where the chrome was starting to wear through. A real mechanic would replace the stanchion without considering any other option and this is quite the correct thing to do. However I have simply rotated the stanchion such that the worn part is away from the wear area. Don't do this at home kids.

It's hard to see but the chrome is starting to wear away on the fork stanchionIt's hard to see but the nickel is starting to show below the layer of chrome. Meh...just turn it around it can wear the other side. 

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Reader's Comments

Alan said :-
Excellent guide Ren. Hopefully it will be a long time before I have to do this.

I like how you have the stanchion pointed at your window. Admittedly cheaper than a new head but a severe blow to the wallet if you fumble the catch. :)

22/12/2016 15:42:46 UTC
Ren - The Ed said :-
HA! Well spotted Alan. Yes I had it pointed at my window, I was aware of this fact but far too lazy to actually re-arrange the wood and the fork in the vice. It could have been an expensive act of idleness.
22/12/2016 21:17:18 UTC
tahrey said :-
Hmm, guess there was a redesign between the CG and the CBF - I started out loosening that top "bolt", with a spanner because all of my 17mm sockets have mysteriously vanished (?!), only to have it PWOING a couple feet in the air and onto the garage floor... thankfully undamaged. Turns out, it's actually the top/spring-securing nut doing double duty. Which is going to be fun when it comes to resecuring the fork in the yokes, because I had an experimental go at screwing it back in and got nowhere, simply couldn't keep sufficient, even pressure on it for long enough whilst also turning it to catch the thread. Arrrgh.

One thing I did find helpful, mentioned on a different site, was loosening the bottom allen bolt as the first step after removing the front wheel (I've started with the left hand fork, so caliper is still in place). It did need quite a shove to break the seal, so I can imagine it would be a hell of a job to pull off if you then needed some way to keep the stanchion from spinning within the outer tube. Luckily I found my 6mm allen key had a short leg *just* long enough to fit in the bolt head and allow 60-ish degrees of turn without being obstructed by the outside of the fork itself, so I could do the initial half turn or so with much more ease than if I'd had to insert the long leg and turn the small one. After that, there was suddenly a lot less resistance, so I considered it loosened. In the kitchen afterwards, the allen key could be inserted as illustrated here and spun with gay abandon, the bolt soon coming out without any trouble.

The innards look mostly the same as your illustration, however I found it largely unnecessary to pull out and dismantle all the bits. I've still done it, in order to extract as much old oil as possible (the stuff was milky black, like some kind of eldritch ichor from a horror movie, definitely don't want any of it left behind), but it would have been possible to get most of the oil out and change the seals without a full discombobulation - just yanking out the stanchion then putting it back in again afterwards.

I have, however, hit a snag that I think means I might be stuffed. The old seal looked sort of like your illustration, but it absolutely did not want to come out. It was like it had been melted or glued in. All attempts to remove it gracefully, with a variety of tools from screwdrivers and kitchen knives to several different types of pliers and even scissors, trying to notch it, soaking the whole lot in boiling water to expand the metal and soften the rubber, etc, were met with absolute resistance (yes, I took out the circlip, I'm not that thick). Eventually I just had to resort to snipping, tearing, and scraping it out a little bit at a time, and removing the resulting burring with a sanding wheel on my cordless drill (and of course wiping out the chaff). A small circular spring was found between the lower washer and the upper lip of the inner fork leg that the seal was wrapped around and removed...

Greased up the stanchion with fresh oil, and my brand new seal likewise. Pushed the seal into position and got ready to send the stanchion through it... Oh. Hang on. Um.

...it won't go in. I mean, clearly, visually, it's not going to go in. The aforementioned lip in the top of the fork leg is clearly in the way, and is barely any wider than the stanchion. There's absolutely no way the seal would fit within or around it even if I used a hydraulic press to ram it in there. It stands a few millimetres proud of the top of the housing, with no way left even to fit the dust seal, let alone the replacement circlip.

Every other potentially suitable seal I can find an image of online looks the same. It's certainly not the case I've been sent the wrong one. The new one even has the little circular spring in the right place, only it would require an act of teleportation to go in.

So, uh... now what? This bike has been a bit of a weird one, Honda themselves say it's registered as a Titan rather than an actual UK model, despite being an ES4 (...dating from 2006) on the V5. The fiches for the Titan models show slightly different parts for the suspension, but the sketched outline of the seal looks the same and it's the same price. Maybe they experimentally put a wholly different set of forks on one batch coming out of the Manaus factory, then forgot to tell anyone?

...or is the metal a part of the seal itself (I couldn't identify anything similar to the ring you describe cutting into, whilst trying to remove the old seal), and it has through neglect and corrosion (there was a LOT of aluminium oxide cack around the top) fused into and become part of the inside of the fork itself? It sure acts as if it's a welded-in piece, absolutely no suggestion that it's in any way moveable, or anything other than a structural component.

Is the clock telling me that it's Dremel Time?
30/10/2018 22:27:18 UTC
tahrey said :-
Side note: I think the allen bolt might need threadlocking when reinserted, if you don't do that as a matter of course (I have no idea where my bottle of TL has gone...). There was something rubbery and gunky stuck in a few of the threads. Or it might just be cack from decayed oil and sealing rubber?
30/10/2018 22:29:21 UTC
Ren - The Ed said :-
It's kind of hard to help tahrey because I cannot visualise the parts your talking about. To be honest the only bit that needs a bit of tapping is inserting the new seal, the rest should go together quite well. Some pictures may help
31/10/2018 10:05:57 UTC
tahrey said :-
Ah, I meant to come back and update this, pending photos. Which will have to come out of my phone, which is not an easy process.

Long story short, what I thought was part of the inner part of the leg, and that had got parts of the rubber seal stuck "around" it, was actually part of the old seal. I didn't realise that they had metal rings inside them until I took a closer look at the new parts and the penny dropped. The old ones had been in there, untouched and unloved, for so long without any servicing being done - witness the awful state of the oil - that not only had they frayed at the edges but they'd essentially become little short of welded in place.

Dug out my half broken Lidl Dremel-a-like and a pile of spare cutting discs, and followed a method closer to what you so copiously illustrated for the second one, just with a lot more than two cuts (I think ultimately three or four closely spaced at one side, and then another four evenly spaced around the rest of the ring). After which, with a bit of jemmying and leverage with a screwdriver and rubber mallet... it suddenly collapsed in on itself and could be much more easily, carefully scraped free of its bond with the inner housing and pulled out more or less in one piece, with just a couple of scraps left behind needing excised with needle nose pliers.

Applying a similar method to the metal part left in the first leg (actually before the above, as I did them one at a time) saw it come out even easier, though there was more mess left behind it thanks to my initial misguided efforts.

After giving the races a buff with a mini sanding wheel, cleaning out all of the swarf, applying a helper film of fresh oil, and heating up the housing until it was nice and toasty, the new seals went in relatively easily at the hands of a 1 1/4" AF (I think?) socket and the mallet.

Was sick enough of it all by then that I just did up the allen bolts without threadlock. We'll see if they start leaking or fall out. As there's a copper crush washer and quite a lot of spring force (which proved to be a complete bugger to fight, getting the double-duty top bolt back in; eventually found that a mini sliding-bar socket driver was the only way, as it allowed me to put constant pressure on with one hand whilst turning the bolt with the other) keeping things in place, it's probably a redundant measure.

Everything seems to work fine now it's back in, but time will tell if I've stuffed it.
07/11/2018 22:16:31 UTC
 

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