Model A - magneto chain case

 The magneto has been sitting on its platform behind the engine for some while, ever since it came back from Tony Cooper. I'd left it off because I wanted some time to look at the seal between it and the back of the gear case, and I'd also posted some questions on the AOMCC Facebook page to try and learn about the two breathers that route out of the gear case and onto the chains. This post is about those two issues.

Let's start with some pictures. This is a page from the 1930 heavyweight parts book:

This is I think an S21/1 oil pipe union with its associated union nut and a broken nipple.

You can see it in situ here. The parts book identifies two of these unions and the other one fits into a hole right underneath the magneto chain run which is not visible in this picture but the whole is clear and the thread is good.

Club member Michael posted these three pictures on the FB page. This is a 28 bike which is not the same as 29 or 30 but gives you a flavour of what they would have used to implement these breathers.

The equivalent bike on '29 and '30 bikes appears from the back of the magneto chain case as shown here:

We will use the illustration in the parts book to invent something to head cross to the primary chain from here. It will have to have something to attach to though, to stop it wobbling about.

These pictures shows the rear chain oiler on Michaels '28. Above, we see the pipe emerging from the timing gear case and disappearing in front of the gearbox - mine will be similar, but it comes from the bottom of the magneto chain case as I said.

What we are seeing in the picture below is the other end of the same tube emerging from a gap in front of the gearbox and running along the frame rail under the gearbox sprocket, flicking up and over onto the chain. This is shown in the 1930 parts book picture above as item A6/683, but just to confuse you the parts book picture is upside down.

This is the relevant page of the 1930 parts book. We can see here that there are two S21/1 unions called up so we can be confident that if we can replicate the one we've got, will be good for the other. The next puzzle is to work out what the A6/120 component does.

This last picture shows the three elements of the magneto to chaincase seal. Left to right we have the retaining washer, the Vellumoid washer, and the felt washer that pushes up against the chain case. The Vellumoid washer is basically a thick gasket that sits across the front of the Magneto - Vellumoid are actually still trading as gasket manufacturers. It's all in reasonable shape and I put it back in as I found it.

SQ4 - maintenance

 After a run to Norwich today, 55 miles at 27.4 mph average speed (according to my new Beeline sat-nav) the Square started making an odd noise on the way home, a bit of a squeak from the engine sounding perhaps like a leaky head gasket. I stopped for coffee at the lovely Itteringham community shop:

After going on to reserve on the way home, I thought I would have a look at the plugs and do a compression test and the picture shows the result. All four plugs are the same colour, dark chocolate, all dry, numbers two, three and four all gapped to 18 thou but number one was gapped to more like 25-28 thou, which I corrected.  

Compression figures are good and consistent at 130-140 psi.

Restarting the engine after I had put the plugs back in revealed that the squeak had gone. Now I am worrying about the oil pressure on the last part of the trip home...

FH - oil from the drive side cylinder

 I might have mentioned a few times that the hunt master has been burning oil from the drive side cylinder, manifested as an oily exhaust pipe, and oily spark plug, and smoke when pulling away. It's always done this ever since rebuild. I had been hoping that this was just really bedding in but after 550 odd miles I think I have to admit there's something wrong. Since it's back in the workshop for its 500 mile service the rocker box has to come off anyway to retorque the head and we can do some investigation.

I had hoped that the rocker box drain might be blocked and excess oil being sucked down the exhaust valve guide with a poked down the drilling with a bicycle spoke reveals the hole is completely open - as I had expected since I cleared the hole out during rebuild.

Removing the head revealed this - a bit of an oily mess on the drive side (that's on the right of the picture) and a fairly normal looking though dark combustion chamber on the timing side.

And then this! That bear piston crown is the drive side, the one that is smoking. There is barely any carbon deposit there at all compared to the other side which looks quite normal to me. It should be noted that the mixture is quite rich at the moment as the mileage is not really high enough to do any proper plug chops.

This is the timing side exhaust valve.

And the drive side exhaust valve, looking a lot hotter.

Here is the upper side of the head gasket - that is the side that touches the head itself. The area within the red ring shows I think a leak from the cylinder into the head bolt drilling and possibly into the drive side exhaust valve drain. Perhaps this explains both the smoke and the oil coming from the cylinder head joint and dripping onto the primary drive case.

It pays to be careful when removing the cylinder. I released all the nuts and made sure that I collected them all with their washers and put them aside. Next we used the leather mallet to loosen the cylinder joint which was quite straightforward - not forgetting that the forward magneto pickup has to come out to remove the cylinder. 

It's wise to lift the cylinder with the pistons in their uppermost position so that you can lift the skirts above the crankcase mouth to get the couple of pieces of wood into the joint to support the weight of the cylinder. You can then introduce a suitable cloth into the gap to prevent any broken bits of ring or circlip falling into the crankcase. 

Once you have lifted off the cylinder the wooden battons can support the pistons.

Removing the cylinder very carefully reveals two pistons in very good shape - to be expected since they have only done 550 miles. The purpose of this exercise of course is to check that the rings are sound and indeed they are so we can take some comfort in the knowledge that the compression test we did months ago is supported by rings which appear to be in very good condition.

Investigating the head gasket sealing area and the bolt holes reveals a couple of interesting points. Well, one main point really and that is that most of the cylinder head bolts open into a gap between the fins, a few fins below the head joint and secondly that one of the front middle two bolts doesn't pull down properly as the thread appears to be very tight. This is in the area where we suspect the leak to have been.

We will leave this for now as I have a day on the railway tomorrow and some other bits to do. I've made a post on the FH Facebook group to make sure that I've selected the right tap to clean these threads out!

Model A - rear wheel

 It's over 35° C here today, and I don't feel like doing very much so I have been pottering about clearing up the workshop and listening to The Fellowship of the Ring on Audible, read by Andy Serkis.

When all the loose bits were put away I set to to remove the rear wheel rim by undoing all the spokes as I did at the front. Very therapeutic!

The rear brake drum for 1930 features this bolted in ring which is designed to retain any loose spoke heads and prevent them getting involved with the brake shoes - Ariel must have had some mishap to make them realise this would be a problem.

The ring is held in place by three square headed 2 BA bolts which come out easily.

Here is a close up:

The next step is to clean and scrape years of gunge and grease from the brake drum and hub.

The spindle is all present and correct, except that it is very slightly bent. We straighten this out with some heat in the vice.

When it's clean we can put a couple of coats of black gloss on the hub.

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.