FH - update from the bench

 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...

SQ4 - a useful modification

 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.

SQ4 - after the service

 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.

See that bit of debris half way along the spring? I cleaned that out, and after a suggestion from Richard in the AOMCC, I changed the ball and reseated it.

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.

FH - still on the bench, but looking good!

 It's been a while, or it feels like it. It's actually almost a week since I did anything to the FH - I've done a couple of railway turns and the weather has been a bit wet.

The head bolts are torqued to 32 lbs ft or so. I tightened them down using a 1/2" square ratchet (as per the manual, as tight as I could get them), then checked them with a torque wrench set to 32 lbs.ft. - so they may be tighter than that. The 32 lbs.ft seems to be bandied around a lot in connection with iron-head A10s.

This is the drive side cylinder - 140 psi or so. this was showing 75 psi on the last test, and is the cylinder that weeps oil.

This is the timing side cylinder, which showed 95 psi in the last test.

Now, obviously these numbers are a lot higher than we saw before, but don't be fooled, this is partly because I had the throttle open during the test - it was closed previously. The big win here is not the high numbers, but the fact that the two cylinders are no longer 20 psi, or around 25% different.

I bought a couple of sets of rocker box gaskets on eBay - they are identical to BSA A10 rocker box gaskets, though the tappet cover gaskets are different. I fitted these with Wellseal last time, and destroyed them lifting the rocker box. This time, I'm going to use Threebond 1215 on one side with grease on the other.

I'll have to find a moment to put it on.

FH - back to the bench

 After returning to the road following the split oil line incident, the FH has now clocked up 270 miles and it's high time to retighten the cylinder head. There are a couple of issues - it's still leaking on the drive side, and it puffs a bit of smoke from that side as well. Perhaps the return oil way is leaking oil both into the cylinder and out of the joint, onto the fins. We know from this post that there is a compression problem, and the behaviour demonstrated during the compression test supports the head gasket leak theory.

Removing the tank reveal this nasty fretting damage to the rocker oil feed pipe. Given that this pipe and it's banjos are in the way when the rocker box comes off I think I might cut the pipe here and fit a bridging rubber piece so that I can remove the banjos easily with the rocker box next time.

With the rocker box off I could get the spanners back on to the head nuts. I got quite a bit of movement on the central ones so I'm quite optimistic there will be an improvement in the compression figures for the drive side cylinder. We shall see when it's back together.

Not surprisingly perhaps but I discovered that you can't do a compression test with valves that won't open and the bike on the bench, because you can't fill the cylinders and you can't get enough purchase on the kickstart to give it a proper kick.

Never mind. While I'm under the tank I thought I'd have a look at these broken grease nipples for the steering head - this is the first time that I've successfully used an easy-out for anything!

I fitted a new one from stock, but I've only got one unfortunately...