Model A - carburetter investigation

In a spare moment while waiting for parts I thought I would have a look at the carburettor provided with the Model A kit. I've not touched it since it arrived all those years ago:

In the last couple of days I have removed it and giving it a good clean so that I can discover what's missing and what's broken.

It's the original carburettor and is pretty worn but it cleans up well:

Standard fitting for the 1930 Model A is a 6/112 carburetter, now called a Pre-Monobloc, which is 1" throat diameter, and here is the evidence:

According to the Amal book, jetting is as follows:

• Size: 1"
• Main Jet: 4/042-160 (still available new)
• Pilot Jet: none
• Needle Jet: 4/061-106 (still available new)
• Needle Position: 6/065, position not recorded
• Slide: 6/0524
• Float chamber: 14/004

The slide is really bad - probably the worst wear I've ever seen. The grooves around the top of the needle are in pretty poor shape too - we should expect this and the needle jet to need replacement

The choke slide spring appears to have been cut short - fortunately I found a spare one in the carburettor bits box.

The float chamber appears to be correct - I didn't expect the bowl to be held by those two brass fittings at the bottom - there must have been a gasket in there

Initial observations:

• The main jet is missing
• The needle looks very tired 
• If the needle is tired the needle jet will need replacing 
• We probably need another cable adjuster 
• The slide is very bad which probably means we need a rebore from Joe the Carb.
• We need to understand how the float chamber fuel feed was sealed - possibly by some sealant in the thread

That's it for now - it's back on the bike and we can start some other jobs.

Model A - painting

 In my quest to put the primary side back together to clear the decks before starting to investigate forks, we come to a little painting job on the chain cover and clutch dome.

I've cleaned up the clutch dome with a 40 grit flap wheel, 60 grit paper, and degreaser.

This is the first coat of Tractol 816 grey primer supplied by Smith Allen to go under the Tekaloid 318 gloss black.

It goes on easily and dries very quickly but it does seem to hold brush marks and attract dust.

Twelve hours later, with a slightly larger brush I applied first top coat:

It goes on very nicely but I seem to have trapped quite a lot of bubbles. Perhaps I am over working the paint.

I put a second coat on the next day - after nearly 6 hours it was still slightly tacky. The second coat could be handled in 24 hours and these two parts are now hanging from the workshop ceiling to cure.

As everyone says, the depth of the gloss is amazing.

Model A - Primary chain

 Today I have fitted and tensioned a new 1/2" x 0.305" primary chain, which for the record has 80 pitches. If you recall, this bike has a new 23 tooth engine sprocket:

The 23 tooth sprocket I've fitted is the largest one Ariel offered in 1930:

This appears to correspond with an 80 pitch primary chain, though I'm sure 79 pitches would fit as the chain is nearing the end of the adjustment. Perhaps the 80 pitch chain is designed to suit the Burman clutch.

A 79 pitch chain would need a half-link which I believe are available from Simply Bearings. I might investigate that, but I don't fancy having two spring links in the chain.

W/NG - mileage

 It occurred to me recently that the mileages I record against each of the maintenance activities in my spreadsheets are inaccurate for bikes which have had their engines rebuilt since I've owned them. 

This issue is not really a problem for any of them except the W/NG which I rode for a while before I rebuilt the engine, so the engine related maintenance activities are not being held at the right mileage. 

This became a bit of an obsession for a few hours following my return from a two week trip to France for my daughter's wedding. After a bit of digging I found this receipt for the speedo rebuild:

Since I didn't have any records of any activities against maintenance activities, though I have hundreds of blog posts recording to work I have done, I went through all the pictures I had of the bike showing the speedo and recorded the dates and the mileages:

• September 2017 - first ride in my ownership
• February 2018 - 185 miles
• September 2018 - 383 miles
• October 2018 - 422 miles
• August 2019 - big service, documented in this post, probably about 600-650 miles.
• August 2020 - the engine rebuild, probably at around 1000 miles
• March 2022 - 1485 miles
• February 2023 - 2023 miles
• April 2023 - 2124 miles
• April 2023 - 2133 miles
• August 2023 - ridden to Tom's, and pictured in this post. It stayed there for two years.
• September 2025 - retrieved from Tom's as documented in this post.

As will be seen in this blog, various small jobs ensued and the W/NG is now the daily rider. Maintenance is now properly documented in it's own Excel spreadsheet - listed in this page.

Model A - kickstart spring cover: 3rd and final part!

 Honestly, this will be the last post about this kickstart - it's gone on far too long! To be fair though, making the shaft was probably the most complicated machining job I have ever done and I had no idea what the spring cover looked like - so forgive me three blog posts on this subject.

We are at the end though, the cover has been raised a little bit to reduce the clearance between the distance piece and the gearbox end cover and it's been cleaned up and painted.

Once I got a couple of coats on the spring cover I fitted the spring and gave it another blow over to cover over any damage.

And that's it, fitted and finished.

Apart from greasing it... might need another blog post?

Model A - Kickstart spring cover 2

 After lots of input from the Ariel community, I now understand how the kickstart spring cover is supposed to work. 

There are four parts in play, illustrated by this page from the parts book:

• LS254, the kickstart lever. I think I have the right one
• LS262, the kickstart bush. This comes all the way out of the end cover up to the end of the shaft, LS253. The bush is 1 3/8" OD
• LS263, the distance piece. Andrew H of the AOMCC tells me that this is 1 1/2" OD, so the wall thickness must be something like 1/16".
• LS264, the spring cover

The big reveal is that it is the distance sleeve that keeps the spring cover in place, and that it is itself kept in place by the kickstart lever. This means the spring cover, LS264, must fit tightly enough around the bush LS262 to be retained by the 1/16" thickness of the distance piece LS263. 

The other thing I've seen is that the top of the spring cover is not flat, but follows a nice radius. The former has been back to the lathe for reshaping:

I've prepared another bit of sheet, by cutting it to size, squaring the ends and removing the paint:

Before we start on that, I found a piece of exhaust pipe the perfect size for the distance piece. I made a wooden former so I could cut it to length in the lathe and form a short radius on the end.

The radius prevents it sliding towards the gearbox quite successfully and it fits rather well behind the kickstart lever.

I formed the spring cover in the same way that I did last time but there was no way it would shrink far enough to get to the required inside diameter for the kickstart bush, so I ended up cutting darts in it and welding them up

There is a bit more work to do, but all the bits fit together. I think the spring cover is too long but I always knew I would have to trim it and I need to finish the welding. Lastly there will be a hole for the spring to pass through.

Before we get into that though - this is my latest invention for welding - an arm rest! Makes controlling the torch so much easier:

The arm rest made finishing those tiny welds much less stressful. The welds were backed with a curved copper strip which as I have shown before minimises the dressing required on the back side and gives you much more control when welding this thin material. It's been welded, ground out inside, straightened, ground outside and so on...

Next job is to drill a 1/4" hole near the edge, and file it oval:

Then I've used a drill to form the material such that the spring can pass through:

The spring is wound in from above:

In the video, the spring cover has been trimmed to length and fitted:

It's not perfect but it's nearly there. I shall raise the edge of the cover a little more since the whole assembly has to account for end float in the kickstart shaft, and there is a bit more clearance than I would like.

W/NG - a bit of maintenance and a run out

It's a beautiful day in Norfolk and after doing a lot of routine maintenance it's time for a quick run out to warm up the oil prior to changing it. We make a 20 mile round trip to Cromer to do some shopping.

On the way back we stop at home to drop off the contents of the panniers and find something interesting - leaving the bike running on the field stand reveals that it smokes on the field stand - and drips oil from the decompressor.

The reason is obvious when you think about it - the rocker box is drained down the pushrod tubes and on the field stand the whole rocker box is higher on the push rod side and will fill up with more oil than it would when standing vertically. Consequently oil goes down the valve guides and out of the decompressor...

The picture above is the giveaway to this theory - here the bike has been standing outside Morrisons for 10 minutes on the field stand but not running. There's barely a drop of oil on the ground and what there is is on the timing side. It comes from the magneto to chaincase connection I think.

Still, the decompressor shouldn't leak so we'll have to have a look at that yet again. 

I wondered whether the main nut was square to the rocker box and was successfully making a seal there but it appeared that the decompressor body thread was loose enough in the rocker box to accommodate any out-of-flatness. What wasn't so good though was the thread - it's 5/8" BSW but it has an undercut down to something like 9/16", so the 3/8" BSP Dowty washer I was using is way too big. Since I don't have a 9/16" sealing washer, I used a 13 x 1.5 mm O ring and a 5/8" fibre washer - we'll see how that goes whilst we order the correct parts!