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...

SQ4 - back to the road

 A couple of days ago, the Square Four came off the bench to be replaced by the FH in order for me to torque down the cylinder head at 270 miles. The Square rolled easily onto the floor as it's great weight dictates with little left to do than fill the oil  and fuel tanks. 

It had been off the road for something like 4 weeks for a service and one evening I ladled in a gallon of fuel drained from the FH tank. It wasn't until I went to start the engine that I realised the fuel was pouring out of the fuel tap. It had dried out. Choosing the easy solution I soaked it in fuel overnight to see if I could get the cork to swell up again: 

This worked a bit but not well enough. The next day found me replacing the cork with a new one and also replacing the two o-rings in the reserve plunger that I made some years ago. 

Finally getting the engine started revealed another problem - no oil pressure. I ran it for 10 to 15 seconds or so with no success and shut the engine down. I realised that I would have to bleed the feed to the Morgo oil pump. I don't believe I have drained the tank before - the last time I changed the oil I didn't wash the tank out so the oil lines from tank to engine would never have been drained since I built the engine all those years ago. 

Bleeding the pump is very easy as it has a built-in hole for the purpose:

I was pleased to find the timing chest very clean and the sprockets and chain in excellent condition with the tensioner working properly. A few minutes with a screwdriver had oil seeping from the bleed hole and the whole thing sealed up again. 

Restarting the engine found the oil pressure leap up to 50 psi immediately. There is a little niggle here however in that normally the oil pressure will rise to 75 psi on startup from cold, but we do have different oil this time. I'm using Motul 20W-50 in place of the old green tin Duckhams lookalike that I used to buy from Halfords. 

Secondly the engine is not running very cleanly, misfiring a little. There may be some investigation to do.

Thread & hex data

 The following page provide descriptions of the threads in common use; the drill sizes, pitches and hex sizes associated with them, and a few interesting tit bits of information...

• Reference Page

It's handy to have it in the blog - makes it easy to find when you are in the workshop.

SQ4 - under the tank

 I've taken the opportunity to remove the petrol tank because it's time I did the valve clearances and had a look at a persistent oil leak that has been going on for years. I thought it was fixed; I changed my mind and decided it was a head gasket problem - but then careful observation of the rocker box oil line revealed some seepage. It's obviously been quite bad in the past at some point, before I fixed it last time, because there's oil on the steering damper plates under the steering head. There must have been quite a jet to get it out there. 

Some years ago I did repair a leak here but it appears I didn't do it very well:

When I took this apart it was clear that they was some oxidization within the joint which had prevented the solder wicking down inside the fitting. I cleaned that up with wet and dry and tinned the pipe with some solder, using plenty of flux to sweat the joint into place. It resists that twisting now. 

The next job is to do the tappets and pulling off the rocker covers reveals some lovely clean valve gear. 

These are all supposed to be set to 0.001" with the engine cold. I used the famous 'Rule of Nine' to set them up. 

Valve clearances all proved to be very close to where they should be - I adjusted a couple of them but most of them were ok. I moved on to the spark plugs - cleaning them, checking their gaps but again they were all ok.

This one is from cylinder number 4, but it's fairly typical of all the others. You might think it's a little dark on the centre electrode and indeed we might consider adjusting the mixture a little. We could put another washer under the float valve to lean out the mixture across the whole rev range.

I took the opportunity to change the thumb nuts holding the HT cables to the plugs for some larger ones that I made some years ago.

With the rocker cover off I took the opportunity to snug down the head bolts and nuts. This is quite straightforward except for the pair that are buried in the fins - these two at the back are particularly difficult and you have to take the carburettor off to get at them. The one on the timing side of the bike is almost impossible because the casting has not been cleaned up sufficiently for you to be able to get at the nut.

Next time that I take the head off, there will have to be some grinding in there.

Reassembly was quite straightforward, apart from getting the oil tank back in. I've now 'adjusted' the area above the engine plate and below the frame rail with my favourite (small) hammer. It goes straight in now, but you have to remember to take the oil supply/return manifold off the engine first. You can't get the oil tank bottom bracket past the oil lines with the lines in place.

SQ4 - rocker shaft seals

 These wet black rings are the fibre washers that seal the ends of the rocker shafts. They get very hot and are subject to oil seepage from the rocker box. 

I need some new ones.

They are not a standard fibre washer - they have a large outer diameter of about 3/4 inch but the hole in the centre is for 5/16 inch - unfortunately they are out of stock at Draganfly:

So here are the bits we need. At the top of the picture there is a 20 mm punch which I have turned from bit of handlebar on the mini lathe. Below that is the special washer and the nut that fastens the rocker shaft in place; top left is the punch used to make the central hole. The new washer is to the left - it's the grey one. 

Below is the mangled original.