Model A - dynamo drive

 I have been wanting to sort out the dynamo drive for a while - not having it in place leaves a lot of parts laying around on the bench that I want to clear up. It was hindered by having to make a special puller for the dynamo bearings, something that I use infrequently but is very necessary if you're going to rebuild one of these dynamos.

Having finished the puller, I spent a little while turning up a short spacer. For some reason the replacement armature is a little shorter than the original though it fits where it needs to!

And I needed to file up a Woodruff key for the dynamo drive sprocket. It actually took me a long time to get to this place because I had inadvertently assembled the dynamo and fitted it with the dynamo body the wrong way round which caused the sprocket to be something like a half an inch out of line!

Here's the drive in place

That was a chain in amongst the past that came with the bike - is the correct 3/8 inch pitch but the width is way too much. I'll have to look at simply bearings and see if I can find another one, but it really needs to be endless.

You can see here that this over wide chain will rub on the crankcase.

Mini-lathe - front stay spacers

 The mini lathe proved its worth again today and gave me two useful parts from some scrap.

These are 3/4-in diameter by 3/16-in thick spacers for the Model A and the W/NG, with 6.5 mm holes to clear quarter inch screws.

Here is where they fit - what they do is give you a little bit more room between the fork leg and the mudguard stay to stop the brake rod rubbing.

They will be chemically blacked in the next batch.

FH - insecure centre stand

 Some while back I wrote about adjusting the stops on the centre stand to get the wheel off the ground and to enable the bike to roll on and to roll off the centre stand relatively easily. A few months using the bike has made me realise that it's far too easy for the bike to come off the stand and since my son has had it he's remarked on it a couple of times.

I need to do something about this. 

I recall that when I bought the shock absorbers I was encouraged by fellow riders to go for a longer shock absorber option to make the bike easier to get on and off the stand, which it does. The bike is actually fitted with 310 mm shock absorbers - the standard is 300 mm, or more probably 12 3/4".

Stripping one of the shock absorbers finds an M10 by 1.25 pitch thread on the damper. An option would be to increase the length of this thread and then chop the excess 10 mm of the end of the damper rod. This won't be too much of a problem except that I don't have the suitable die and if I can't remove the rod from the damper I will have to cut the thread with the die but leave no undercut which will be untidy. I can't remove the rod from the damper, because the top of the cylinder is rolled over.

My first step was to ask the supplier if I can buy the damper units without the rest of the shock absorber, and these turned up for about half the cost of a new set:

The next step - and it's never straightforward is it - is to modify the spring compressor. The problem is that the compressor now has to reach so far down inside the spring (because the damper is shorter) that I can't get the pin in through the damper eye. 

I sorted that out by chopping one end of the pin off, trimming the end and welding a washer on the end to act as a head. 

Next I will rebuild one shock absorber and then turn my attention to the other. When that is done it will be time to remove the centre stand and adjust the stops.

Square Four - another clutch

 Well, I recorded in my last post that the Square Four clutch was slipping badly, so badly that as I rode it up the hill back to the workshop the engine speed was soaring and it was clear that the clutch was on its last legs.

I've said many times before that these bikes are very easy to work on. One thing I've always done when accessing the clutch is removed the footrest - but actually don't need to do that. All you have to do is remove the nut and rotate the footrest on its mounting out of the way - you don't have to break the taper at all.

Even before I dismantled the clutch it was clear what happened - you could smell the burnt cork and there were bits of it everywhere. Stripping the clutch down revealed carbonized cork inserts - I could put my finger through these and they would just disintegrate.

Fortunately I had a spare set of 90 corks - that's enough for three plates - sitting in the workshop. Once I'd spent a couple of hours cleaning the mess off the plates I put these in boiling water for a few minutes.

You can push them in with your fingers - or a bit of wood is sometimes useful. It does make your fingers hurt after doing all of them, but it doesn't take long really.

I thought there was one missing - so I rescued a wine cork from the bin.

It's easy to slice these up into the right shape.

As it happened, as soon as I started clearing up the plastic bowl I've used to soak the corks I found the missing one so I didn't end up using my homemade one.

A couple of hours work had all the plates re-lined.

When you put new corks in, I always fit them to the bike wet. When you initially fit the plates they will only just be retained by the basket slots but the next day you will find they have settled a lot. You can see in this picture that the first friction plate is now well into the slots - this is about 24 hours after reassembling the clutch and all the corks are now dry.

I tested out a couple of days later, and readjusted the cable. The bike started straight away though as normal the clutch was stuck - I have always had to free the clutch before starting this one.

Sheringham Classic Car & Bike Show

 About this time in June, every year, Sheringham hosts the annual classic car and bike show. We've had a wander around most years and the Square Four has been to a few; this year son Thomas came, bringing the Huntmaster back to Sheringham from his garage in the city.

It's time for the 500 mile service and general checkover and the bike appears to be going well.

He says he has a list of jobs for me - some of which I'll do and some of which I'll quietly ignore... 

It's quite mucky and appears to have leaked all of its fork oil over the rest of the machine. It's also smoking as it always has done but that really needs looking at.

He says the clutch is slipping - and it is adjusted rather too tightly. On entering the show the marshals made us ride at walking pace behind a Rolls-Royce Corniche which was quite testing for these air-cooled machines. When it came for departure at 16:00 the Huntmaster started straight away and I rode it home but it was clear that the Square Four clutch was slipping far too much to start the bike. I got the tools out in front of The Crown - the garden was packed full of people so I had an audience as I slackened off the clutch cable. 

Fortunately that was enough to get sufficient torque through the clutch to kick it over and start it - which it did first time. It's slipping really badly and it's clear that it's been too tight like the Huntmaster one and that the slow ride through the town was too much. 

Note to self here - keep enough play in the clutch cable!

Model A - front forks dry build

 You might remember from the recent girder fork investigation post that we had a lot of movement in the forks - in fact a 3/8 inch variation in wheelbase. It was obvious that a lot of this was down to wear in the links and wear in the spindles.

I contemplated reworking the original links for a while but while chatting to the AOMCC Black Ariel spares specialist I discovered that reproduction links were available from the club at a good price, so bought a set. They're not perfect - for example the middle links are smaller in diameter than the originals so I will keep the originals and repair them at some point.

For some reason the top links on the 1929 and 1930 bikes are not fully threaded:

The club spares officer also recommended I bought a new spring. It's certainly true that old fork springs I've used in the past have been very soft and looking at the old spring previously it was clearly a bit stretched. Again new ones are available at a reasonable price:

Putting these bits together with the old spindles revealed a significant reduction in play.

A few days later, the new spindles arrived from Acme Stainless - and very nice they are too. On bikes of this era, you don't need the knurled washers - these arrived in 1934. I bought a pair of headstock nuts as well since I was one missing and pulled up the steering head bearings a bit more. 

Putting all these in place removed all of the play in the forks. I now cannot detect any variation in wheelbase.

Stuck in the steering column there is the beginning of the blanking plug that is used on the Model A which was not supplied with a steering damper.

That plug will be chrome plated eventually. I'll finish it machining it long before that happens!