2013-08-22 15.10.41

Now the real fun starts!

Let’s put this jigsaw back together!

Please be patient, there are a lot of hi-res pictures to load on this one!! There are a couple of points to watch that, being a Velocette, it has in common with most of the other models (regarding the clutch at any rate) and a few that are unique to this model, like the re-mounting of the outside flywheel…

Today I want to cover the replacement of the primary chain case and all that this procedure entails… A little different to the average four-stroke Velocette that we all love and know (perhaps intimately).

To start off with, the primary chain case is a but different to the later models. In this one, It also incorporates the dynamo drive in a unique to this model configuration, between the clutch and crankshaft, as opposed to forward of it. I was loth to disturb the assembly of the primary-drive sprocket on the end of the crankshaft from the dynamo-pulley, and so the following procedure was followed: First of all the inside casing had to be affixed to the clutch end of the gearbox on the drive side. The cork Gasket there was examined and found to be good, the surface of that in contact with the gearbox was smeared with blue ‘Hylomar’, non-hardening “aerograde”, which is my favourite since about 30 years for this sort of thing (used to be called something different then). After pressing the cork back on to the gearbox, the FRONT face of the cork has to be smeared with a liberal coating of high-melting-point grease…

2013-08-23 10.37.40

Please notice that clutch thrust bearing has also been replaced in this shot, with a ‘new old stock’ item, whose one face was a bit blemished, so the best side goes inwards to the face the balls in the cage (You may remember that the old one was ‘shot’…)

2013-08-22 15.16.08

Just as a reminder what the race looks like, here with some ‘assembly lube’ sprayed on… before the outboard-facing plain ring goes on.

The reason for the grease is easy to explain: The inside casing has to fit over the the ring around the crankshaft that is on the crank-case and the back end has to be up against the gearbox. The gearbox, however, has to be free to move forwards and backwards to adjust chain tension in the primary chain… SO, after that, the inner PCC can be attached with the 4 screws to the gearbox and wired up, so that they just pinch and a quarter turn back. I used galvanised fencing-wire… The front of the inner PCC is placed over the ring on the crank-case and it should all fit, with the dynamo sticking also through a hole, as well as the square brake-pedal and foot-pedal bolt…

2013-08-22 15.28.32

Here it is, showing the clean inboard side of the Primary Chain Case, which goes up against the greasy gearbox.

2013-08-23 10.51.20

Here it is fitted and nicely wired up, the wires nice and stiff and out of the way of the clutch pusher-offer.

2013-08-23 10.51.30

Here a bit closer.

That’s the easy bit! Next comes whole of the front side of the PCC and the drive off the crankshaft. In this case, I didn’t want to split any more than was necessary, so the drive-sprocket off the end of the crank was still attached THROUGH the outer PCC to the pulley for the dynamo, onto which the actual crank-shaft-flywheel attaches ( just a bit different to the four-strokes!).

To put his on, I first made a new gasket for the Primary Chain Case as shown here:

2013-08-22 16.04.23

The outer shape is easy and is simply traced with a pencil around the perimeter.

While the case is sitting on there, the holes can also be penciled onto the gasket-paper through the holes in the casing, remembering to keep the pencil vertical and sharp!

Cut out, best done with scissors: Don’t forget, in this particular case, that the outside of the chain-case is not the same as the outside of the gasket! Turn it over and you will see that the gasket has to fit INSIDE an edge that has been turned over, and so must be at least 1.5 mm smaller all around…


Cut his first and then measure with a compass (borrowed from one of the children/grandchildren) the width of the gasket required at the face of the inner Primary Chain Case…

2013-08-22 16.09.18

… and transfer appropriately to the paper all around the edge

2013-08-22 16.15.08

… and then cut the inside out, preferably with a scalpel or other VERY sharp knife, or failing that, it can also be done with scissors.

2013-08-22 16.32.43

The holes can be punched using various tools (there are all sorts of hole-punches available. Even one of those leather-punch-pliers will do the job well.

2013-08-22 17.20.16

The inside face of the outer PCC suitably spread with gasket compound and the gasket pressed into place in the outside chaincase.Here it is easy to see the turned-down edge that the gasket fits inside, which is why it had to be trimmed around the perimeter before marking out for the inside cut.

2013-08-22 15.55.47

The clutch can then be placed on the gearbox end of the sleeve-gear

2013-08-23 11.46.19

… NOT forgetting first to check that all THREE pins are still present in the clutch assembly…like I did! When I placed the clutch on the table, the one pin dropped out and I didn’t notice until I had fitted the outer… another 15 minutes undoing all the screws and then taking the clutch off, put the pin back in and re-assemble… Happens every few years or so… No one else has EVER done that before, though, I suppose!

2013-08-22 15.56.58

The clutch nut is then screwed on so that it all doesn’t fall off (using here a tool actually designed to remove lens-rings on cameras!)

2013-08-23 11.26.40

The primary chain is then rotated onto the clutch and readied to be put on the sprocket on the inside of the outer chainguard.

Now comes a tricky bit… The perimeter of the inner chain-guard then has gasket goo applied, the front sprocket is brought closer and has the chain rotated onto it and the sprocket/ pulley is pushed over the crankshaft end (assuming that the gearbox has been previously positioned so far forward to allow this!!)

2013-08-23 11.28.19

OK, after this, assembly of the PCC is simple enough, the screws are replaced in their appropriate holes and all is good.

2013-08-22 17.31.05

Now the ‘cotton-reel’ is replaced on the front of the PCC/Engine mount

2013-08-23 11.41.05

The dynamo pulley and belt can now be replaced. Put the belt on the crankshaft pulley and the other end in the dynamo pulley and slip the pulley over the shaft with the belt on, unless you want to undo everything and do the rotate-to tighten procedure all over again. It’s no good putting the pulley on first, obviously, as the belt WON’T won’t fit over the lip – believe me!

2013-08-23 12.15.31

Tighten the nut on the pulley, of course, before putting the cover on over the top.

2013-08-23 12.33.23

… and the large nut that holds the pulley on the crankshaft can now be put on and tightened. Clean the threads meticulously and screw the nut on tight.

At the first attempt, I found that the nut turned the crankshaft before tightening on the pulley, so the pulley needed to be driven onto the taper of the shaft to affix it first, to avoid premature rotation of the engine, which slightly hinders the tightening of the nut…

2013-08-23 12.30.59

For this, a large, deep socket was used and cautiously but firmly whacked to seat the the pulley onto the taper, so that it did not rotate…

Eventually it worked, the nut was tight and the flywheel could then be attached by the six nuts.

2013-08-23 12.50.45

The washers under the nuts were cleaned up

2013-08-23 12.53.57

… and the nuts done up opposite to one another, to pull the flywheel evenly into the recess.

2013-08-23 12.40.12

Once pulled in and checked for egocentricity (hic!), the nuts were removed again and a spot of Loctite applied, the nuts now done up for real, ready for painting!

Well, that was about it for now, the mainshaft is then dutifully replaced in the gearbox and tomorrow, the rest of the assembly will be updated!!


© peter gouws 2013

Made on a mac