W/NG - a puncture

Another unexpected event this week - a puncture. Strange, because air suddenly started hissing out of the tyre after I'd been standing in the workshop for an hour - the bike hadn't been out for days. 

I had a spare tube and resolved to fix it with the tools I had on board, just to prove that I could. 

The wheel came out easily, even with the panniers in place, though one of the top hat washers on the drive side (the repro one) was very stiff in the slot. I skimmed it in the lathe. 

Proving that tyre changing is all about technique, the cover came off easily. 

Unusual puncture - the tube has fretted against an unused security bolt hole in the rim:

It's gone through the rim tape too. 

Nothing much here, but I pulled off this old canvas tape, wire brushed the whole rim and laid a piece of the old tube over the hole to reinforce it. 

Having inspected the brake, which was showing nice even wear, I replaced the tube. 

The cover went on without any drama, though initially I forgot you have to start opposite the valve to avoid nipping the tube. 

Job done - almost. The connector hose on the pump was completely knackered. Luck was on my side, because although I inflated the tyre with my workshop pump I found I had a genuine Apex pump with its long connector in stock!

W/NG - An unexpected event

A few weeks ago I was cracking on home on the W/NG, doing 55-60 up the North Walsham by-pass (the old Midland & Great Northern alignment to Honing) when she suddenly cut out. After finishing the ignition checks I kicked it over to find apparently no compression. I popped the exhaust valve cap off for a look, found nothing and a few minutes later she started OK and carried me home apparently fine.

Stuck valve perhaps? She was pretty hot...

At home, I put the endoscope down the bore for a look and it was clear there had been a partial seizure at some point. Thinking about it, there had been a squeak from the rear tyre and a little shimmy at the back end, and I'd had the clutch in very quickly.

Pulling the head off you  could see the scuff in the bore very clearly:

The rings were OK, apart from the fact that the second ring was tight in it's groove. Hardly surprising really:

Rightly or wrongly, I polished this out. Doubtless someone will tell me I should have replaced the piston.

I built this tool to hold the barrel while I honed it - it's just a couple of bits of plywood:

You can mount it in the vice either way, but this is the most convenient for honing. I mounted it vertically to grind the cylinder head to barrel joint.

I used a cylinder hone to clean up the bore. Hopefully these honing marks will retain a bit more oil...

I also replaced the inlet valve guide which was very loose - the new one had an interference fit in the head but was a smaller bore size - too small for my valve stem. I bored it on the lathe to change the diameter from 5/16" to 3/8", but writing this post I've realised I probably have an exhaust valve in the inlet position... 

Anyhow, it's all gone back together and is running beautifully, apart from a pesky leak from the decompressor. I've reverted to fibre rocker box gaskets (I can't get the aluminium ones to seal) but I've still got a weep from the decompressor, which has a very worn stem. 

It'll take a bit of work to fix that as I want to re-engineer the sealing arrangement, but that will have to wait. It's been OK for the last 70 years. 

Mini-lathe - Another little accessory

A tool height guage! This handy little accessory is made from a bit of 1/2" square bar, polished on the bottom face where it stands on the bed ways. The vertical bit is a piece of strip welded to the base, with a notch at centre height. 

It's used to set up the tool height so it's in the desired position relative to the spindle axis. 

Mini-Lathe - A couple of modifications

It's been a while since I wrote anything about the workshop but recently I made a couple of small modifications to the mini-lathe that I'd like to record in this post. 

First up, a new chip guard made from a 2 mm sheet of perspex, mounted on a steel arm with a strong magnet to sit on top of the lathe:

Secondly, I have modified the sleeve nuts used to retain the splash back - these now comprise a 20 mm spacer and a shorter sleeve nut; the splashback now sits 20 mm further back and is no longer fixed directly to the bed. This means that:

• chips can be pushed into the tray from the splashback and removed from the front
• the cross slide goes to the end of it's travel without hitting the splashback first.