It is difficult to find an old C90 without knackered wheels and mine was no exception.
I am not sure what the wheels had been painted with but it was rock hard and there was no way they could be cleaned up satisfactorily, so I decided to replace the spokes and rims. There are three options:
- Hand them over to a wheel builder
- rebuild the wheel yourself
- buy pattern replacements
Aftermarket replacement c90 wheels are available, however, you need to replace the hubs, brake panels, spokes and rims as a single unit as the aftermarket parts are not always exactly the same sizes as the originals. Because I wanted to keep the bike original where possible I decided to have a go at rebuilding the wheels myself. Being clueless about wheel building I wanted to minimise the number of things that could go wrong so I decided to get OEM rims and spokes.
The c90z2 front and rear wheels are both the same size (17 x 1.40) and the rims have been made by various manufacturers over the years. My original ones were made in Japan by Araya, although they are no longer available from this manufacturer. Futaba made the rims for more recent bikes, although these too have been discontinued. The current Honda supplied rims are made in Indonesia by D.I.D (David Silvers can supply them for UK and US folks).
Once you have your rims you need to submerge yourself into the thrilling and confusing world of spokes.
Four types of spokes are used on the 1978 C90 z2 and there are subtle differences between each one: the heads that lay on the outside of the hub are right angled, whereas the spokes that fit on the inside need a wider angle to allow them to fit properly. The rear spokes are thicker than those on the front wheel and are also “butted” (thicker near the head).
As with the rims I decided that to play safe and use OEM spokes, ensuring they fit as Honda intended and minimising the number of things that might go wrong when I tried to lace the wheel:
72 spokes are needed:
* butted spokes
Note that Honda changed the c90 wheel specs over time so you will need to check the parts manual to confirm your specific spokes (the parts lists are available online at CMS). Note also that the nipples need to fit the holes in the rim (the nipples are 5.1mm diameter on the z2).
Patient ebay shopping got me 46 of the required 72 spokes at about a £1 each from suppliers of new-old-stock. Annoyingly the ones in short supply are the expensive rear wheel ones so I had to buy most of those new (£3.30 each at the time!)
Once you have finished emptying your wallet it is time to lace the wheels.
lacing the wheels
Lacing is just one of the wheel building black arts and this is my layman’s summary of what I found out from reading and having a go at doing it. Needless to say, wheel building is an entire trade in its own right, so what I say below should be taken with a pinch of salt!
Step 1 is measuring the offset on your rims. The rims on the Honda c90s do not sit exactly on the centre of the hubs but are offset to one side. In the world of wheel building this is apparently known as “dishing”. Everyone seems to agree that you should try and build your wheels with the same offset as the originals, but I’m not sure what would happen if you don’t.
Measure the offset by putting a straight edge agains the flat face of the hubs and measuring the distance to the rim, if you want to get a fair measurement it is sensible to measure at several points and take an average.
You can then cut off the spokes. Although I had no intention of reusing them, as an experiment I tried to unscrew some of the old ones: about 1 in 10 would come out, the rest were rusted solid.
The offsets I measured were 12 mm for the rear and 9mm for the front. I have seen another account from someone who took much more care measuring than I did and his measurements were 12mm and 7mm respectively, although this was done on a more modern c90. I wish I had been more careful with my measurements, as I am now not sure if the different results are down to difference between the models or just a result of my sloppy use of a ruler.
Unfortunately I have now cut all the spokes, so I can't check it again.
Lacing is not difficult and is just a matter of following the instructions. This is a good explainer video:
Despite the clear explanation above I still managed to do it wrong first time on both wheels. To be honest, I am not entirely sure where I went awry, but I suspect that I simply picked the wrong hole to start the 2nd row of inside spokes (the holes on either side of the rim are staggered, one of the holes is nearly aligned with the one above it – that’s the one you want). The chap in the video does actually explain all this (see 4 min 15) , but I seem to have missed it (for both wheels):
If you start off wrong and keep going you will eventually find that the remaining spokes can’t reach the rim. With hindsight the signals are there long before that point: as soon as you find yourself having to tug at the spokes to get them to go in this is a sign that something has gone awry – they all fit without any pressure when you get it right).
At this stage you just need to loosely do up the nipples. Here are the spokes laced onto my newly repainted hubs:
Wheel truing is another of the wheel building black arts and no doubt fixing seriously bent or damaged wheel is highly skilled, but with enough patience the basic techniques are within the grasp of the rest of us, particularly if we make the job easier by starting with a new rim and new spokes. The steps to follow are explained well by the chap at Oakys garage:
Once you get a feel for it is not too difficult and if you take it slowly you will get there in the end. The idea is to get the rim of the wheel roughly straight and offset from the hub by the appropriate amount and then to gradually tighten the spokes, keeping an eye on how true the wheel is as you go. You will need to reinstall the wheel bearings if you removed them to paint the hubs and a jig is needed to hold and spin the wheel as you work. I was aided by a purpose built wheel balancing jig, but you may be able to improvise by holding the inverted front forks in a vice and spinning the wheel on its axle.
The jig is surprisingly well made for something that was produced in a factory in China and shipped all the way to my house for a grand total of £29.99.
The original Honda spoke nipples are 5.1mm diameter and this is not a standard size. I bought a cheap multi-size spoke spanner and slightly filed out the no 11 slot (below)
As far as I can tell from the people in the cycling world, when it comes to spokes the rule is the tighter the better just so long as it does not distort the rim (this would be hard to do to a motorbike rim, which are much more substantial than your average bicycle wheel). I did mine as tight as I felt comfortable – the result is that they all have a musical ‘ping’ when tapped. Here is one of the finished wheels:
The Honda manual says that new wheels are delivered from the factory true to within 0.5mm and should not be allowed to runout more than +/- 1.0 mm. That little blip you can see in the video is less than that, honest!
wheel bearing removal
If you are replacing the wheel bearings, extracting the old ones is a bit of a faff. There are proper tools for the job - called blind bearing pullers - but if you haven't got something similar you'll have to do as I did and improvise.
The bearings in each wheel are separated by a spacer and, once the axle is removed and the tension is off the bearings, there is just enough wiggle room to insert a metal drift from one side and get it onto the edge of the inner race on the opposite side. After that, with a bit of judicious tapping, you can knock out the bearing. Note that when doing this all the pressure is applied to the unsupported inner race and - because this might damage the bearing - it should be replaced.
It took me a while to figure out how to get the bearings out and in the process I damaged the spacer on the rear wheel. I'm not sure if it really matters but I replaced it just in case. The new spacer design has changed from the original - perhaps it would have been a bit less fiddly to get the drift on the spacer with the new version.
wheel bearing installation
There is a proper driver for reinstalling the replacement bearings but if you haven't got one you can improvise with a suitable sized socket (you need a socket that will align exactly to the outer race of the bearing, or an upturned socket that will contact both the inner and outer race at the same time - pressing on the inner race or the rubber seal will damage it).
It might help to gently heat up the rims before installing the bearings (a low-mess way to do this is to wrap the hub in a towel and then poor on boiling water). I also put the bearings in the freezer for a bit and mine went in with a few gentle taps.
Ball bearings are installed with the manufactures's name and size code facing out (so they are visible from the side the bearing is installed from). This is done as a courtesy to people who are working on the machine after you are, since they will able to see the bearing size without having to remove it first.
The speedometer cable is turned by a worm drive installed inside the front brake panel:
The worm is driven by the speedometer gear that is installed over the central boss of the brake panel. The two tags on the back of the speedometer drive gear engage with two of the four notches cut into the boss in the wheel hub
Note that Honda used several different hub, front brake panel and speedometer gear designs over the years and they are not all interchangeable, so be sure to check the correct parts for your model. The parts above are for a 1978 C90 Z2.
rear sprocket carrier bearing
The rear sprocket carrier bearing is a 6203 open deep groove ball bearing measuring 17x40x12mm - I used one made by Nachi (who also made the original). There was no obvious sign of wear on the original, but I replaced it for peace of mind (the bearing is about £5):
There was not much to do to finish the wheels: on the front wheel I replaced the brake arms, springs and spacer (all of which were very badly corroded) and of course I put in new grease seals. Genuine replacements are still available for all these parts
On the back wheel, a new o-ring, brake arm and brake adjusters + new cush drive dampers (these rubber parts act as dampers when power is delivered from the engine to the hub carrier in the back wheel – most people recommend using original Honda parts if you can get them).
In the internationally recognised test for new wheels I bounced them on the floor and no spokes flew out.
The original bearings were sealed on the outside, presumably because there were concerns back in the day that the bearing seals and or grease were not up to the job of long term use. You can prise of one of the covers and grease the bearing if you want to keep it per Honda’s original specs, but modern bearings with seals on both sides (“2RS” bearings) contain lubricants that are expected to last the life of the bearing so this is not necessary any more.
It was only when I looked closely at the diagram in the manual that I understood why there is no instruction to grease the axle:
Before looking more closely, I had a vague notion that the inner races of the ball bearings were rotating around the axle. In fact what happens the whole assembly of inner parts is clamped together solidly as if they were a single component. For example, as you tighten the nut on the end of the front axle, the force is transferred through the end of the suspension arm → collar → inner ball bearing race → distance collar → inner ball bearing race → brake plate boss → steering arm → axle bolt head.
Because the outer races of the wheel bearings are captive inside the wheel hub, and the inner races are pinned in place by the axle bolt and nut, the radial forces are carried by the steel balls inside the bearings. This is why the manual does not show grease being applied to the axle: it does not rotate in relation to the inner bearing races and therefore does not require lubrication (having said that, it doesn't hurt to give the it a light coating of grease, if only to help stave off corrosion and to assist with assembly).
Don't forget to fit new cotter pins when reinstalling the wheels. See below for the correct way to install the cotter pin on the axle: the head of the pin should fit between two of the castellations and the short leg of the pin is then folded backwards over the nut while the long leg is folded forward over the end of the axle as shown below:
that's it for wheels!