The Solex is back on, but I still have a problem with idling - but it's different. The bow in the inlet flange that I removed has changed it's behaviour at idle, as you might expect, but in tuning the idle I've realised that the idle volume screw is very worn.
I've ordered a new one:
While I wait, I've wrapped the old screw with PTFE tape which should help.
With an hour or so to spare, I went to the workshop to finish putting the tank on the Huntmaster. Bolting it down was no problem but I noticed a drip from the tap. The plunger was very loose and I imagined the cork might have dried out since it had been empty for quite a long time. I was wrong about that - the cork was just knackered.
As some of you know I volunteer on the North Norfolk Railway as a steam fireman, trainee DMU driver and trainee guard. Some of these roles need a few bits of equipment which can be bought or made.
Some of you also know that I have a 1930 Ariel Model A which needs two toolboxes and that I have a hankering to make these myself from leather, so I've concocted a few little jobs to learn about the leather work.
This latest one is a little holster for a ticket clipper - that old-school tool that you used to see bus conductors and railway ticket collectors using to make holes in your ticket.
We start with a bit of 2 mm leather, soaked in the sink. Add to that the ticket clipper wrapped in cling film and a wooden form cut to the shape of the clipper plus a few millimetres.
Using the clipper and that form we can squash the wet leather around the clipper until it dries and miraculously it will have formed the shape of the clipper. Behind that there is a thicker bit of leather which will make the backing and the belt loop so that I can carry this around up and down the train.
When I've cut the backing to shape I can use my stitching punches to make the holes for the stitches. This is quite hard work on the thumbs! Since I made my key wallet a few weeks ago I have learnt to stitch in a box shape in order to make the belt loops rigid.
Just a tiny but maybe significant change today - this may be a mistake particularly as I'm changing two things at once - but I have just changed one of the distributor advanced springs.
The Square Four has always had two different springs which is not uncommon and it's designed to adjust the advance curve provided by this simple mechanism.
What I've done is replace the heavy spring with another which matches the existing lighter spring. As you'll know, at the same time I have repaired and inlet flange leak on the carburettor so I am committing a crime against my own rule of changing more than one thing at a time!
In other news, the Solex is almost complete and will go back on tomorrow I expect. The Huntmaster is also done - all I have to do is put the tank back on.
Some while back I retarded the timing on the Square Four and improved starting greatly, but it is still running roughly coming off idle and when coasting. Nothing I do to the carburettor seems to improve this so I have resolved to have another look.
Stripping off the carburettor is quite easy and another inspection revealed nothing new. However looking at the gasket faces (something which I would do every time with an Amal carburettor) revealed a bit of a surprise:
You can see here, by the dark line along the edge of the flange that it is by no means flat, which can lead to a weakening of the mixture. A few minutes on some 200 grit wet and dry paper revealed this:
A few minutes more work improve that even further.
The internal mating face between the throttle body and the float chamber and jet castings was nothing like as bad:
This face did show a little distortion, but it was easily removed. You will note that one of the throttle disc screws is missing - I removed that one but as you can see the other one didn't come out without a fight. The reason I removed it is revealed by this picture:
See the light around the edges? This is ostensibly completely closed! What I needed to do therefore was to remove or loosen the butterfly screws and realign the disc so that it was properly closed. In reality it's not essential that it closes because the throttle stop is there to provide some idle speed and the butterfly will always be partially open. This kind of leakage will prevent you idling as slowly as you might want to so it pays to reduce the gap as much as possible. I replaced the screws and got a marginally better result:
I will work on this some more when the proper screws arrive. These should be raised countersunk M4 screws, around 10 mm long.
This is going to be a very short blog post and is just here to record that the top end of the Huntmaster is back together and currently waiting for the tank to go on, when it will be ready for the road again.
As you can see I have cut the rocker box oil line and bent it out of the way of the bottom of the tank. It now sports a short length of flexible hose and some hose clips to allow the rocker box to be removed without interference from the oil line banjos. The rocker box has been on and off several times getting the gaskets right and developing the sequence of bolting up so the absence of the banjos has been useful.
Yes, the FH is still on the bench after I have been faffing about with the Square Four. The issue is that when I put the rocker box back on I squashed one of the studs for the head steady into its nut and damaged the thread - so the rocker box had to come off again. I decided to buy some new half nuts and reduced hex nuts to tidy up their appearance and I just got round to putting it all back together.
Of course it still takes two goes because as usual I have forgotten that you have to start the nuts for the head steady and the two reduced hex nuts at the rear due to curves in the cylinder head which prevent you getting a nut on...
I've been fiddling about with the ignition timing this week as there had been some significant hesitation coming off-idle and some poor performance at low speed - what we used to call 'kangaroo petrol'.
I retarded the timing a bit and realised the bike had stopped kicking back on startup, and the slow running was better, and it would fly along like a bat out of hell - but coming off idle still wasn't as smooth as I'd like.
In the end, after fiddling with the idle mixture and getting nowhere, I stripped the carburettor.
I didn't find much. Some debris in the float chamber, the flange fixing to the head looser than it should have been, and one of the float chamber screws was loose. I blew out all the jets and ports with carb cleaner and found everything clear.
Putting it back together, I added this little tee to the idle mixture screw to make it easier to adjust (it's a bent bit of brazing rod, soft soldered to the brass screw), and used some Threebond on the flange.
We'll see what happens.
A few little teething troubles appeared after the recent service, most notable of which was the oil pressure. Normally the oil pressure sits at 75 psi when cold and rolling at main road speeds, dropping to 25 psi idling after 15 miles or so.
Today, it was going up to 75, but intermittently dropping to 40 or so - very odd. I bled the Morgo again:
When that appeared to be happy - there were no bubbles I turned my attention to the relief valve.
I then rode to Cromer and back, clocking up about 13 miles - until it warmed up, it sat solidly at 75 psi and was still showing 50 psi when I got home. Back to normal.
It’s a bit snatchy at low speed. Initially I thought this was carburetion (not that I have changed anything), then perhaps transmission snatch, but all is normal there.
I’m going to retard the timing a bit.
