Solex again

Time to start finishing stuff off. I have some new carburetter parts from David Jones from Sleaford, who specializes in the repair of the Solex carburetters fitted to the SQ4.

It's the bi-starter control and the air bell:

All in pieces

Assembled. This is the bi-starter in the off position - that knob is a little long I think.

I have an insulator that I will be fitting as well.

It's a 3 mm thick insulator and it is manufactured from Silicon Resin Bonded Fabric. It is impervious to Ethanol and it is 50% more heat resistant than a standard Tufnol insulator and 100% stronger than phenolic. In an ideal world this would reduce the heat going into the carburetter body and reduce the high-temperature misfire.

In the real world it causes the float bowl to foul the distributor cap and is completely useless. But I did discover that when you inevitably drop the carburetter flange washers and they fall behind the dynamo, you can see them sitting under the dynamo from the rear, if you look across the top of the gearbox. I'm sure if I drop enough down there they will start coming out.

Just like the 2p falls at the amusement arcade.

A post from Mark Walsh of the AOMCC shows me that if an insulator won't fit on my machine, there is something wrong: there is a lot of space on Mark's machine, which already has an insulator:

Mark Walsh's SQ4

Here's the Solex back in place:

You can see I have changed the brass tag that is used to mount the throttle return spring. It now has several spring positions so that I can vary the torque the spring exerts on the throttle spindle - I want the throttle to spring shut, but I want a light action. The second spring position is good for that!

Here's a close up of an earlier version:

Front Brake again

As you all know I've been having trouble with my front brake on and off since my SQ4 went back on the road late last year. This year it has had a lot of attention, and is a lot more effective than it was.

Yet it still 'groans' particularly when reversing but also moving forward, which is probably down to the cable being a little tight and the shoes still bedding it in.

However, I wanted to check with members of the AOMCC forum if anybody's brake plates bend outward (in the direction of the arrow) by a few mm when the brake is applied. This is quite easy to see in the garage. I'm guessing that's not normal.




Something is maybe not as square as it should be. Maybe the brake shoes are able to move out of true, or the hub is slightly conical? Maybe there is some play that should not be available?

The brake shoe linings may have worn lopsided and when force applied the brake plate springs a bit. They are not actually that strong, and normally don't have to resist much force along the line of the axle axis. The shoes may have worn unevenly. The springs may be distorting the way they sit, or the plate may be too close to the wheel hub. Something wrong with the bearing installation.

So I stripped it down again. What I didn't expect was two cracked shoes...



Given that these shoes have a marginally smaller diameter than the drum, and have an adjuster at one end that allows the shoe to be brought into contact with the drum, it's easy to see how this would happen.

The story goes like this. If you do the adjuster up relatively tight, the slightest movement of the shoe brings the friction material into contact with the drum. If there is a gap between shoe and drum at the cam end of the shoe, but none at the other end operation of the cam will attempt to bring the cam end of the shoe into contact with the drum, bending the shoe about the contact point at the adjuster end; the resulting bending moment causes a tensile load on the inner diameter of the shoe, leading to brittle fracture due to the hardness in the casting.

While this brake design is used in every car drum brake I have ever seen, it is invariably with fabricated steel shoes which will be considerably tougher than this cast aluminium.

Splendid club the AOMCC. Not more than a few hours after posting the story of my plight on the forum, Paul Jameson had put these in the post!



Many thanks Paul. I also have this from Draganfly, in exchange for my previous, silver painted version:



So the next step is to fettle it all to fit and get her back on the road.

Huntmaster - Missing parts appear

The Huntmaster was always going to be a long term project, partly out of time but also for want of space. It's lurking about in the garage and from time to time something pops up on eBay, or something else triggers the realisation that a part is missing.

Looking at the engine one idle evening I took the points cover off the end of the magneto only to find they were missing! These K2F points assemblies see to make a lot of money on eBay, so I had to wait a while before I could get one at a reasonable price. Here it is along with the fixing screw:



And here it is back at home in the magneto



And here's another one, this time from Adrie deGraff from Holland. Its the front section of the rear chaincase:

It needs a bit of welding, but this is what it should look like:

And this is the other side:

And what it should look like: