POST 4: Blue bike; Front Suspension: Wheel (hub bearings/seals, brakes speedo drive) and forks.

Dealing here with the blue bike- an obvious problem was that the front brake control was completely siezed. Having come across this before I immediately suspected a corroded  actuating arm stuck fast in the hub, or sometimes the linings can detach from the shoes and jam them inside the hub. In either case it needs sorting and the first step is quite obviously- remove the front wheel. This seems quite straight forward so I took a few pics of the wheel mounting before starting.

Front hub and brake plate RHS- cable entry. 

Close up cable connection

Brake arm hub attachment noting alignment of punch marks on actuating arm and lever.

The right hand view showed that the hub appeared to be leaking grease. There was a spacer installed here- narrower end towards the hub seal.

Front hub- LHS Note spacer

To remove the wheel first remove the cables. The speedo cable is secured by a screw through the rubber terminal block.

Attachment of speedo cable- note securing screw.

 

Here the screw has been removed allowing the cable to be pulled out of the speedo drive unit. I have put the screw back in the hole for safekeeping.

Wind in the brake cable adjuster so that, in an ideal world, you can then ease the cable nipple out of the actuating arm. However, in this case the cable was jammed solid and there was no slack in it at all. It was therefore impossible to remove the cable from the wheel until I'd removed the wheel!

I removed the nut and washer from the RHS

...and tapped out the axle towards the left side. Use the nut to protect the threads.

Front axle removed and parts reassembled in order. From Right side- Nut- washer- spacer and axle end bolt.

To make space to remove the wheel I removed the cross-head screws securing the front mudguard and the wheel could then be removed. 

Once off I was able to get enough room to slip the brake cable's nipple from the brake actuating arm.

Brake cable barrel nipple detached.

The brake problem could then be assessed but to my surprise the problem with the front brake rested with the cable which was jammed internally and permitted no movement in either direction. The brake arm itself was actually free to move and actuate the brake shoes.

I set about easing the cable's movement with copious oiling and was pleased to find that it was rescuable. I cleaned up the hub

... and checked the brake shoes. Both were present and in good condition. Having checked new shoes these are supplied at 3mm lining thickness. The wear limit is 2mm which seems very poor value but mine came in at 2.85mm. Since there is no sign of detachment and the shoes look to be in good condition I'm refitting them. The large (40mm) oil seal was present to seal the speedo drive grease from the shoes although it looked to be in poor condition. Speedo drive gear visible inside.

I was able to clean the shoes and hub, operating the shoes let me remove the old hardened grease on the actuator and replaced this with fresh HMP grease. The Wheel itself was rusty and  looked awful so it was immersed in citric acid solution for a week to remove the rust before repainting. This was remarkably effective and  resprayed the wheel with wheel silver and lacquer. The tube and tyre are both perished and will need replacing.

Having removed the wheel it was obvious that the telescopic forks felt very different left and right. (I was disconcerted by this and decided to strip them to investigate. However hindsight tells me this is probably normal) The rhs pushed in further and much more easily. These will need stripping down but fortunately they are quite a simple design. There is no oil in these forks and no hydraulic damper. The "oil seals" between stanchion and slider are in fact just dust seals and in my case both were badly damaged and brittle, they simply slide down the slider. These will need replacing but are currently not available. Ill need to source some sort of replacement when I reassemble.

The forks are held together simply by a large circlip inside the base of the stanchion tubes. This can be removed  with circlip pliers and the sliders then behave like their name and simply slide out. .

RHS fork dismantled. Note the dust cover has been slipped down the leg and the circlip removed; it wont come off the leg until the slider is removed from stanchion.

The leg drops out of the stanchion revealing its components. The first to emerge is the plastic top hat collar.

... followed by the lower leg (slider) itself and finally the suspension spring. At this point it was clear why this leg compressed so easily- the cylindrical rebound rubber that I had expected to be present inside the spring was missing.

Components of the RHS fork leg- note that it has no rubber rebound cylinder. I dismantled the LHS leg  and noted that the internal design of that leg differed from the right side with a long plastic slider and in this case the reound rubber was present.

Front fork sliders compared. Note that the lhs has an additional pvc slider. I've no idea why this is so. Note that the rebound rubber is present only in the left leg. I'm assuming that one leg is designed to resist compression and the other to resist extension thus achieving damping in both directions? Whatever the reason, it seems an odd setup.

Rebound rubber removed from the LHS fork leg with its spring.

The rebound rubber presents me with a mystery... looking at the parts catalogue for the early models shows that they do indeed appear to have had just one such rubber fitted, and located in the lhs fork leg. The parts list gives the full complement as just 1 rebound. This rubber looks like mine in that its a blunt-ended cylinder. Closer inspection of my own found that it has a hole bored in its base. Overall the cylinder is 18mm in diameter and 70mm long. The central hole is 7mm in diameter and 45mm deep. However, by the time you get to the 1980s and the NC50 III (as this bike), the parts diagram then shows a rebound rubber in both legs and specifies a complement of 2 for the bike. This rubber is a different shape and has a conical top and flat base. Although both these styles are very cheap, listed at just a few Euro each, neither the blunt-ended nor conical style rebounds are currently available. My bike therefore appears to have earlier style fork internals... perhaps externals as well if the whole forks have been swapped from another bike.  This setup presumably should work OK even if I don't understand how it functions. This means I have a choice: I can refit as I found it with a single rubber, try to find a pair of the conical shaped rebounds or find and fit a second of the blunt-ended rebounds. Since no new parts are available any new parts will need to be made. Machining a conical end on rubber isnt possible with my tools, I also do not know whether the conical top replaces the hole in the base- I suspect it does and that both are intended to give some sort of graded compression response. This means I can't make an insert of the more modern type, but making a blunt-ended rebound rubber should be easier. I ordered some 18mm rubber rod and will try to make a few of these myself. 

Hole bored in base of rebound rubber.

I understand that in earlier versions of the NC50 the white plastic collar was replaced by a metal "top hat" collar that was threaded so it can screw directly into the stanchion. These are shown below in a pic borrowed from the fb group (not my bike). Note that these forks had no circlips and the internal parts once more differed side to side... although I don't know why.

I ordered some 26x40mm 10cm long gaiters and will try to fit these using a rubber strip as and adapter  since these gaiters are too large to fit the stanchion without packing. Fitting these would be greatly assisted if I could take the dome cap off the slider tubes to let m slip on the new gaiters. The caps are held on by a roll-pin

roll pin in fork slider cap

Which is easily punched out. However this did not release the cap which could be neither tapped off or unscrewed. Checking the fb group shows that theres no trick... its just tight. I was forced to reassemble and re-evaluate once the new gaiters are here.

Tapping it out with a punch

The end cap could be removed after heating using a drift. Sadly this did mark the cap so I cleaned up the edges in the lathe.

Heat the cap and tap it off- it was too tight to remove without heating.

Cap cleaned up to remove burrs.

I replaced the original and damaged dust covers with 40x26mm gaiters. The 26mm side could attach to the chromed leg being only slightly too wide, but the 40mm side was too large to clip neatly over the stanchion. I adapted this using a strip of 3mm rubber. Iwound this round the stanchion creating an overlap and then cut through both layers at once to get the exact size required.  

Cutting the rubber strip- fit to a tight overlap and cut through both layers at once

There is a recess inside the gaiter top

Top of gaiter as supplied.

The strip of rubber Id cut fitted exactly into this recess and I secured it with rubber glue.

Insert the rubber strip into the gaiter and glue in place.

Strip fitted inside gaiter.

The modified gaiter then fitted nicely over the stanchion and clipped into place above the metal ring on the stanchion base. I will secure it with a gaiter tie.

The  rhs fork could be assembled in the order; gaiter clip, gaiter, internal snap ring, top hat bush and finally the  pre-heated cap could be refitted and re-pinned with the roll pin.

RHS fork reassembled and capped.

The forks have no oil but the manual says helpfully just "grease". This is little if any use. Asking on the fb forum the suggestion is to pack the spring with 1-2 tablespoonfuls of general purpose grease and spread this down to cover the sliding plastic parts. This is a messy job but relatively simple so I inserted the greased slider into the stanchion and secured with the clip ring.

Slipping the slider inside the stanchion- messy job.

I secured the base of the gaiter using the clips supplied although these may need to be changed later when I get the clip strip for the gaiter top.

Gaiter fitted- lower clip in place. Upper clip awaited in the mail.

I'm not sure how this substitution will fare. The advice I've had is that the original dust caps were there mainly to keep out dirt and moisture which the gaiters can do just as well if not better. However, the original covers were also a closer fit over the stanchion and  so must have acted as a grease seal. There is even some indication inside them that they may have originally held an O ring which presumably sealed better against the slider. Time will tell if my repair simply pumps the grease out of the the fork or not. However, I've also heard that some riders use the forks almost if not completely dry  so I suspect the grease isn't needed for damping action.

I replaced the lhs fork with its more complex internals in the same way. Strangely it seems only the lhs fork shows any damping action at all- the rhs simply drops to extend to its full length under gravity (no wheel fitted!) and seems to offer little if any resistance to being pushed back up. The forks remain a mystery! 

Changing wheel bearings

The bearings did feel very rough... probably as acresult of my citric acid doak to derust the rims so it wascalways going to be necessary to replace them. Its a case of 2 6300 zz (double side covered) bearings and a 19 30.5x7 oil seal. This is an unusual size available for Honda. However Im using double sealed bearings so an oil seal here isnt strictly nevessary... its a dust seal really. 19x30x7 seals are readily available although do fit only loosely into their recess.  

First step is to lever out the old bearing.... not usually a problem but this time it was very firm and the seal tore rather than popping out intact (see on).

I then used a blind bearing puller to pull the bearing out upwards

There was insufficient ridge to punch it out from the opposite side but this worked well.

The spacer was then visible inside.

... and just lifted out. The degraded grease of the old opposite bearing is visible beneath. It was a simple matter to tap that bearing out with a drift.

I fitted the new bearing and tapped it home.

Grease and insert the spacer

Before tapping the second bearing into place followed by the oil seal. Here I discovered why  the previous seal had been so hard to shift. The ol seal is the same size as my new at 30mm od. This is loose in the wheel recess and appeared to have been glued. In the end I did the same and used Loctite 603 retaining compound to fix it in place. I set it aside (with the spindle and spacer in place to centralise) whilst the adhesive went off. If this doesnt work Ill try shimming the recess with a ring of 0.25mm shim strip and fix it all in place with the Loctite.

Finally I could fit the new tyre and then refit the wheel  This time I coukd also fit and adjust the newly lubed and functional front brake cable.