Reassembly

 

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Reassembly was pretty much a reverse of dissassembly with a couple of remarks.

Firstly, I had to reduce the brim thickness of the sw arm bushes to 1mm each to allow the washers to be slipped in between bush and frame. This also gave a good swinging fit with no play and aligned nicely with the circlip.

Secondly although the parts book shows the rear mudguard as fitted with 4 15mm M6 bolts, only the top 2 are of this type. The lower 2 are self tapping hex screws fitting into captive nut plates.

Rear mudguard fastenings-hex self tapping lower mount on left, 15m.m6 on right.

I fitted a plain washer and spring washer under the top two and plain washers under the lower.

Remember to feed the rear light cable through the mudguard before fitting the mudguard itself.

The rear tyre was split and unusable so I fitted a new tyre and tube. I cleaned and re-lubed the chain before refitting the rear wheel and chain.  Rear wheel chain tensioners adjusted easily. Pleased that the sprocket does accept the chaun monkey alignment indicator so wheel alignment and chain tension were sorted at the same time. I could then refit the chainguards. Very pleased that now I had knocked the dents out of the chainguard the 2 halves fitted perfectly around the sprocket and overlapped each other very neatly. 

Coming together- moving on to exhaust and frame cladding

Remove the carb and rubber mount before fitting the frame cladding. I realised that the wire and cable runs originally on my bike may well be wrong- and engine cladding plates were missing. I found I could feed the handlebar wiring loom down inside the frame cladding to emerge in the groove above the motor. The wiring from the alternator could also be fed into this groove so that the connections are made inside and covered (eventually) by the engine cover plates. I'm still not sure I've routed the clutch able correctly but this will be obvious when I fit the engine cover plates...*

*In fact this proved to be correct - the clutch cable enters the top of the LH cover plate. The RH plate actually has a cut-out to allow the magneto wires to take this route.

Wiring exits base of frame cladding to make connections to magneto in central groove.

Wiring enters top of frame cladding- clutch cable stays free.

Connections hidden in groove, make sure all connections are insulated.

Exhaust and motor covers fitted

Note motor covers require 2 countersunk m6 machine screws, 15mm and 30mm.

Left cover, kick start and gearchange levers fitted.

Fitting kickstart and gearchange levers- note that the kickstart has 1 large spline that must be aligned with that on the stub shaft. Note the clutch cable entering via its cut-out in the motor cover.

Exhaust fitted- I did buy the correct ring nut from NSU.de. Note the magneto wiring entering motor cover through deficated cut-out at front right

Exhaust fitted- the chrome on this was largely protected by the grease and cleaned up well. Those areas which were too badly pitted were treated and resprayed with a mist of hammerite.

Detail exhaust end cap and brake cable.

The bike was now coming together at a pace but I remembered I had yet to finish the fuel tank which I had eventually had to strip to bare metal and sprayed white. I used fine line tape to mark out the grey areas and then masked off the rest begore spraying.

Respraying colour panels on tank.

I gave the white paint plenty of time to harden before masking, and then sprayed the panels one at a time to avoid getting it wrong... again!

The tank plate screws had been damaged so I replaced them with 6mm M3 countersunk screws.

I have the badges to go back but I need new 6mm M3 countersunk screws.

Tank badges reinstalled... needed new 6mm m3 countersunk screws.

Tank trim still to go...

New bushes and rear wheel reassembly

New bushes are available but expensive. Tbf, the price wouldn't be too bad if it weren't for post brexit postage!

I now know that I need 2 new swinging arm bushes, 2 new rear shock absorber bottom bushes, 1 brake pedal bush and 3 rear hub-to-sprocket-carrier bushes. I will try to make these. The shock absorber bushes at least can be done easily as I've made these for the front, the hub/sprocket carrier bushes are quite large with a thick body and are hopefully machinable. However the swinging arm and brake pedal bushes have much thinner walls and will probably be too weak to make entirely in the lathe. I think I will make these to fit in their respective sockets, but leave the central bore well undersize.  I will then press them into position in their component, and progressively enlarge the centre bore in position by drilling or reaming so that the outside edge is supported as the wall is thinned. The swinging arm bushes will then be line-reamed to give  tight sliding fit with the swinging arm pin.

Brake pedal bush

Using white nylon, I machined a rod to a tight press fit to the brake pedal and centre drilled it to 13mm

Machining the nylon rod- o/d reduced to fit brake pedal and centre drilled to 13mm.

I inserted the bush into the pedal by pressing it in using the vice.

Pressing in the bush

Bush fitted

And reamed it to 14mm internally

Clamping the pedal to ream the hole. I enlarged it progressively using an adjustable reamer.

Before refitting the pedal. I left the bush slightly longer than the pedal's width so that it could be trimmed to give a good fit up to the circlip once washers were added each side.

New bush fitted and arm slipped on

Swinging arm bushes

I have the size appropriate Delrin rod so I'll go ahead and make some exactly as I did the brake pedal bush. However, I need to leave a rim or "lip" on the inside as these bushes have a "top hat" shape here illustrated from the quickly.de website.  These are the same bushes s used in the Quickly F23 and TT.

The rim of the hat fits against the inside of the swinging arm and together with the washer between swinging arm bush and frame, so its thickness will be crucial in ensuring a good fit up to and against the shaft circlip. I'm not that impressed by the apparent obsession with circlips on this bike. I'd prefer the brake pedal, swinging arm and shock absorbers to be mounted with a decent thread and nut which would of course allow any clearance to be adjusted. 

But then I found that any such "rim" or lip had completely worn away on my bike and this hadn't resulted in excessive side-to-side play so perhaps its not that important?

Remnants of bush in my sw arm. Note the crumbling degradation spreading internally from the edge. The "top hat rim" part had completely vanished from the internal side of the arm.

Although the bush did seem to be operating, it was clearly degrading. In fact it had become so spongey and soft that I couldnt press it out. I had to gently separate it into pieces and ease each out with a screwdriver. I then cleaned up the socket with Emery cloth.

Socket cleaned ready for new bush

I made a new bush from black Delrin rod. I only had 25mm rod which was a little too large. To make the bush I reduced this to 20.3mm (0.3mm squish) over a 30mm length. I then centre drilled and bored it using increasing drill sizes to 15.5mm. I reamed it to 16mm in the lathe and finally I parted it 1mm beyond the reduced length to leave a 25mm brim attached.

Completed bush

Base view of bush and 'top hat' shape

The new bush fitted nicely inside the arm socket and was pressed home in the vice. The 0.3mm squish proved very satisfactory but the bush did close up in the pressing process and had to be opened up again.

Insert the bush by hand and press home in the vice.

To open it up I progressively enlarged the hole using an adjustable reamer and pilot to ream it in line with the opposite bush.

Line-reaming the new bush

I should add a note that although the bush did close up, it was easy to ream it in position. However the "squish" is important for this as reducing the squish to 0.15mm meant that the bush would rotate rather than ream! If doing this again I would explore reaming to 16mm in the lathe and fit with a smaller or non existant squish to avoid it closing up again. 

Also its not really necessary to line ream the bushes as, being Delrin, they have sufficient flexibility. However I would line ream phosphor-bronze bushes in British bikes so I just did it the same way.

Hub bushes

The sprocket carrier fits onto the hub using 3 drive pegs which fit through 3 hub bushes. These are listed in the parts catalogue as  "vulcanoflex" which suggests they were originally rubber and presumably acted to take up shocks in transmission, a little like the cush rubbers in a honda cub. However new replacements  currently available are plastic, and appear to have been 3D printed. Given this, I decided to make them out of Delrin which should give shock absorbing capacity app. equivalent to the new plastic style of bush. Obviously this will be less than the original rubber.

I machined a 25mm rod down to 23mm which was the diameter of the openings in the hub, and centre drilled to 12mm. I could then turn down the insert section to 20.3mm diameter over a distance of 12mm and then parted the bush leaving a 2mm thick collar of full width (23mm) to generate the "top hat" shaped bush.

These bushes were then pressed into the hub and tapped home.

The sprocket carrier was then pressed into the three bushes. I had expected the carrier to contact the hub as it had when I'd strippped it. However, there were no bushes at that time, and now that I have fitted some the behaviour was different. There was a stand-off of 1-2mm between the two, even when the carrier was tapped fully home. This is I believe, due to a slight flare at the base of the sprocket carrier's drive pins. I am currently checking that this is correct, but at present I'm assuming it is, and that this clearance is intended to prevent the sprocket carrier from wearing against the hub since fkexibility in the bush means that the two must move relative to each other when drive is taken up.

Bushes pressed in but bearing looks a bit dented and didn't rotate completely silently.

More bushes

Sprocket carrier inserted- note stand-off between the carrier and the hub.

Bushes inserted- hub bearings replaced- good to go!

Thanks to the fb group for confirming that the stand off between hub and carrier is supposed to be there, and for the picture below demonstrating this from an assembled bike.