Tuesday, 5 July 2022

SQ4 - New tyres

One of the things I have always admired about these old machines is the ease with which you can remove the wheels. OK, so I do have a QD rear wheel on the SQ4 and the W/NG is a little more difficult but at least I have two stands and can remove both wheels at the same time! try doing that on a modern bike.

Something that is less impressive is the front brake adjuster, which doesn't fit any of the toolkit spanners - it appears to be 2 BA across the flats, but it is a pattern part so perhaps that is the reason. I have a 2 BA spanner in the toolkit especially for it.

The front stand is very useful, though you have to lift most of the engine weight to use it. The trick is to make sure it is slack enough to swing down, and then tighten it up again.

The reason for all this was that the Avon Speedmaster & SM MkII tyres are now 9 years old and it's time to replace them. I've bought a set of Avon AM26 Roadriders, just like I put on the CX500 back in 2019.

I might tackle that damaged paint on the brake drum before they go back on. But then again, I could just as easily do that when it was on the bike and get riding it again!

Friday, 3 June 2022

SQ4 - Oil Leak from the Rocker Feed

 This may be a seminal moment in the history of my SQ4. For years it's had an oil leak which I have always assumed to be poorly sealed pushrod tunnels at the head joint. However, having addressed a problem with a leak from the oil tank cap, something else which it has always done, I resolved to look at the drip from the rocker feed pipe. 

The oil tank cap has always had a weep from the breather:

Which translates to a wet leg on a long, fast run:

Looking at that first picture, I got to wondering why the cap has a vent hole when the tank has a piped breather that I have taken past the rear wheel. Surely the cap should be sealed?

It turns out that Square Fours don't use the same cap as other Ariels. I noticed that the 1951 SQ4 parts list has a -32 number for the cap - most bikes (other than Square Fours) I've seen use a -29 number. Maybe 5854-32 has no breather hole.

A blob of solder will sort it.

Onto the rocker feed. I ran the engine cold (75 psi on the gauge) and as the oil warmed up the leak appeared:

Now, my bad - I forgot to take a camera to the workshop when I fixed it. It turned out the tube was not pushed into the fitting at all - it was just held in place with a fillet of solder at one end, and had been like that for years - probably eight years. It's been leaking for most of that.

All fixed now.

Wednesday, 11 May 2022

Charlie's Shed - adapting threads

The FH kit came with a lot of original Ariel cables, most of which were pretty rusty but which still had their original adjusters and nipples. The cable layout changed with the advent of the swinging arm bikes, in that the mid-length and gearbox end adjusters moved up to the handlebars for the front brake and clutch. The thing is, most of the handlebars out there use the later 5/16" BSF adjusters, but Ariel used the earlier 1/4" adjusters to the end. Guess what? Levers with 1/4" adjusters are like hen's teeth!

So what to do? after looking at eBay for ages, and noting that Draganfly are out of stock I decided to modify what I had by sleeving the existing 5/16" thread. The issue is that putting a 1/4" thread inside a 5/16" thread leaves very little wall thickness, so the part would be weak. Here's how I set about it:

First job is to turn a bit of scrap brass to the correct OD - 5/16", and put a thread on it - these are BSF threads in these levers, by the way - so it's 5/16" x 22 tpi. Next, we can drill a hole, tapping size for 1/4" BSF, but we won't tap it yet. Next we can try it out in the lever perch and if all is well retain it with some Loctite 263 high strength thread locker:

Next job it to file the ends flush, and tap the hole. Currently I don't have a tap long enough to go all the way through, but it's long enough for the adjuster. Cut the cable slot with a hack saw and a needle file:

Job done!

Tuesday, 10 May 2022

FH Dry Build - Speedometer Bracket

Today's little bit of progress is this - a speedometer bracket folded up from a scrap of flat bar. 

Monday, 9 May 2022

FH Dry Build - Carburetter

 Some while back, actually in this post, I outlined the trial fit of the carburetter and the fact that the shiny new bell mouth didn't fit very well - as you see here:

Having checked the threads for damage I concluded that the undercut on the carburetter body wasn't deep enough, and/or that the last thread was not cut fully to depth since the new bell mouth did not want to screw fully on. 

I noticed that the horrible plastic one had a short length where the thread was relieved, and not wishing to set the carburetter up on a face plate and recut both the thread and the undercut, I put the bell mouth in the three jaw chuck very lightly to avoid distorting it:

I relieved the thread with some very light cuts for a few millimetres - the bell mouth fits perfectly now: