Model A - painting more bits

 A rewarding but seemingly never ending job is painting bits for the Model A. The wheels are off and the brakes are currently in pieces and here we are with two brake arms and the torque arm for the front brake.

These are the two brake plates, with the paint cleaned off with a Scotchbrite wheel and coated with primer:

These bits had their second coat of black on the 31st of July 2026.

Model A - more painting

 This isn't very exciting post but it's important to make it to record when these items had their first coats of paint. This Tekaloid takes a long time to dry fully - about 5 weeks - and I want to know when I can assemble bits.

Today I have used the wheel to strip rust and old paint from the battery tray, the rear chain guard, the oil tank and the dynamo chain guard.

They have been degreased, had a coat of primer and their first top coat.

The second coat went on on the 9th of July.

Model A - front wheel

One of my key aims is to get the machine rolling so that I can get it off the bench when I need to, to get the others on the bench for servicing etc. To that end I sorted out headstock bearings and the wear in the forks, but of course we still have no tyres and the wheels are not fit to have tyres fitted.

I thought I would change away from my normal method of dismantling a wheel, involving bolt cutters, and see how feasible it was to dismantle it nipple by nipple. I sprayed each nipple with Plus-gas months ago and I was pleased to find them all come apart easily.

Before long I had a fully stripped hub and brake drum, a pile of loose spokes, nipples and a rather rusty rim - a WM1-20 which might get reused one day if I can ever buy tyres for it.

Despite worrying about whether I'd made the right decision with respect to the rusty nature of the rim, the spoke heads confirmed that rebuilding the wheel was a good thing to do. Several of the spoke heads are about to pull out of the hub:

After a short period of decreasing, scraping of general muck and abrasive removal of rust, I put on a coat of primer

Followed by a couple of coats of black gloss:

The black powder coated rims have been delivered from Devon along with spokes and nipples but we will need to wait something like 5 or 6 weeks for this paint to harden before we can build the wheel. More of that later!

Model A - painting

 In my quest to put the primary side back together to clear the decks before starting to investigate the forks, we come to a little painting job on the chain cover and clutch dome.

I've cleaned up the clutch dome with a 40 grit flap wheel, 60 grit paper, and degreaser.

This is the first coat of Tractol 816 grey primer supplied by Smith Allen to go under the Tekaloid 318 gloss black.

It goes on easily and dries very quickly but it does seem to hold brush marks and attract dust.

Twelve hours later, with a slightly larger brush I applied first top coat:

It goes on very nicely but I seem to have trapped quite a lot of bubbles. Perhaps I am over working the paint.

I put a second coat on the next day - after nearly 6 hours it was still slightly tacky. The second coat could be handled in 24 hours and these two parts are now hanging from the workshop ceiling to cure.

As everyone says, the depth of the gloss is amazing.

QR50 - a bit of a service

 After three years in the field, the little beast is back. The boys are complaining the bike has no power after ten minutes running and with busy lives, my son and daughter in law have no time to check it out - so it’s back to Grandad’s workshop.

The Square Four is now off the bench to test the kickstart against the clutch, and then close up the clutch, refit the exhaust and test ride it. All went well with that, so the QR can go on the bench:

The first thing to attend to, and rather alarming, is the fact that the fork top threaded inserts are both loose. Now, these had a ring machined into them which allowed them to sit in the top of the fork leg, which I welded into the fork leg. Now, there is no evidence that the ring was anything other than an interference fit around the insert - indeed, there is no evidence that the insert was anything other than an interference fit in the fork leg.

Now, the inserts are retained in the fork leg by two strong plug welds on each side of the leg:

Next job, the tank. The wrap hasn't survived very well on the tank - the shape is small and complicated. I've pulled it off and treated it with some special plastic primer:

The primer is actually clear - ignore the grey bit, that was an experiment with the ordinary PlastiKote primer to test adhesion: it doesn't work very well, but the special stuff is excellent. This RS Paints Honda Helios Red doesn't come off:

The lack of power appears to be down to the choke - the choke cable goes into the carburetter through a plastic nut which has broken, allowing the choke cable to come out. When it comes out, it appears to operate the choke such that the mixture is rich all the time, even with the choke knob pushed in. That will certainly lead to a lack of power.

The part of the nut that was broken retains the boot, which in turn retains an elbow and the cable.

I turned a new part up from brass and pressed it into the old nut, which I had bored to suit. It starts very well:

As you can see at the end of the video, it dies if you fully open the throttle - the kids were complaining that it didn't have much power. The float height is bang on:

It appears after a lot of searching and cross checking Honda part numbers that a Keihin PA26 carburetter with a #78 main jet is correct for all years of QR50 production. This is the main jet out of mine, which is marked PA 28D but still has the 12.2 mm throat of the correct carburettor:

A #58 is not a #78! It looks like it gets very weak at full throttle, something born out by the colour of the plug. I've made a new carburettor spacer while I wait for the new jet:

A few days later, the new jet arrives as expected - but it's the wrong size. Some of these little carbs use a jet with an M7 x 0.75 mm thread, and these are available; unfortunately mine uses an M6 x 0.75 mm thread and these are not available. So what I did was measure the diameter of the new #78 jet using a range of small drills - I found that a 0.8 mm would not go in, but a 0.75 mm would; the #58 would accept a 0.55 mm, but not a 0.6 mm. I concluded these Keihin jets are identified by their diameter.

One option would be to put the new jet in the lathe and reduce the diameter, and I probably would have gone down this path had I possessed a M6 x 0.75 mm die (it's a fine pitch) but I didn't fancy buying a die or setting up for single point threading, so I did something that ideally you should never do and drilled the old #58 jet out to 0.75 mm, which might leave it a bit lean.

It doesn't run out of breath at high rpm any more:

It's got a new set of tank decals too:

FH - Prepared for paint

Here are the pictures of the Huntmaster bits that I'll use to catalogue the bike for the painter:

FH - it's coming apart!

 I think all this post is going to do is perhaps convince readers that I am actually doing something. It's coming apart for painting. 

QR50 - Fork Bushes

As you know, I have decided to make a new set of telescopic forks for the QR50 since I can't find a new pair locally, or anywhere else for that matter, for a reasonable price. You've seen how I recovered the sliders and stanchions with new tube, and replaced the missing dust caps with machined parts.

Now it's time to machine the bushes and assemble the bits. I bought a 30 cm length of 30 mm white acetal, and cut off two 80 mm lengths, planning to make a complete leg-set of bushes in one setting. I wanted to make sure the set-up for the 22 mm bore was done without removing the material from the chuck.

I made a drawing to set my bush lengths against the existing design and the springs I had bought:

I set one of the 80 mm lengths up in the 3-jaw and centre drilled it, opening it up through 6, 10, 13  and 19 mm for the boring bar.

Here's the boring bar in action, taking out a 40-45 mm length to 22 mm or so to give a sliding fit on the stanchion.

From this bored part, I finished the top bush OD to 29 mm and parted off.

The top bushes fit in a 29 mm ID register in the slider, which is made from 32 mm OD seamless tube of 2 mm WT. The bush has a 0.5 x 0.5 mm register in one end to let it sit just below a circlip groove in the slider.

The circlips are wire type - I bought the sheet metal type initially before I realised there wasn't sufficient space in the leg to house them. Wire types are harder to get out but occupy much less space. The nominal 30 mm circlips need the ends trimming:

The clips fit in the end of the slider nicely - there is a 0.5 mm deep groove about 8 mm in, to let the clip retain the top bush:

The slider has a ground channel to allow you to get a scriber under the circlip:

It's very hard to see, but the circlip ends are ground flat to allow you to lift the ends out of the grooves:

The bottom bush is essentially a blind tube - bored 22 mm for the stanchion and finished to 28 mm OD for the slider, it has a 5 mm thick closed end to seat the spring. It's loosely retained to the stanchion with a small roll pin.

This shows the complete assembly, with the dust cap, main compression spring and the rebound spring. The springs were bought from ebay, selected for wire diameter and OD.

Here's the stanchion in paint:

The frame is also almost finished:

By the way. This interesting effect is called fisheye, and is what happens if you don't degrease the parts prior to painting...