SQ4 - sump plate

 The sump plate looked a bit mangled when I took it out after the oil was drained.

After degreasing I cleaned it up using some clock cleaner which is an ammoniated fluid used for stripping the corrosion from brass and copper. It works very well on the gauze.

When I got it clean, I manoeuvred the washer that stiffens the hole for the oil pickup pipe out of it's wire prison. I managed to get it back into place and squeeze it tight to retain the gauze.

With that done I could think about refitting the sump plate. I destroyed the gasket completely when I removed it so I needed to make a new one. 

With a sump plate it's easy to cut a piece of gasket paper to the right shape and to mark the holes.

Punching the holes is the easiest way to make them tidy and I used the corner of the sump plate to complete the ring of gasket around the holes.

I cut the centre out with a craft knife - it will be big enough to use for something else.

When I drained the sump, there was around a cup full of oil coming out and of course the gauze was damaged. The pickup pipe was the cause of both of these problems in that it was out of position - too high and off centre. It's just a copper pipe retained with a bracket inside the crankcase so it's quite easy to bend it into the right place.

With some Threebond 1215 the sump plate is back on and the plug fitted.

FH - building up the miles

 This week, we are mostly decorating in Cromer! The FH now has 205 miles on the clock, and is still smoking a tiny bit and leaking a bit of oil, possibly from the head gasket.

Here it is, collecting caulk from Screwfix and CO2 from Argos...

I've checked the points today and am pleased to record that they haven't closed up.

I also checked the QD hub nuts after an unusual sound began from the back - they had loosened off a lot.

There's no picture, but yesterday I rode a couple of miles along the main road at 1/4 throttle, killing the engine and coasting to a halt. The timing side plug was brown on the centre electrode, black on the outer. I won't be making any carburetion changes for the moment!

FH - looking for problems

 I snatched a few minutes in the workshop today to look at the cylinder head leak and the oily exhaust on the Huntmaster. It passes a little bit of smoke from both cylinders but nothing persistent and only when pulling away. To start the investigation and to try to eliminate the valves and valve guides and further home on the problem I thought I would do a compression test. 

I started with the drive side, which is the side that is showing oil in the exhaust pipe. This revealed a figure of something like 65 psi with the cylinder dry. Perfect compression at 7.25 to 1 should be giving us something a little over 90 psi.

This didn't improve after several kicks.

The timing side shows us something like 95 psi. The exhaust on this side is dry.

I ran a bit of oil around the top of the drive side piston in an attempt to improve the sealing and to reveal either a head gasket problem or perhaps a valve problem.

This wet test brought the compression up to 75 psi - still a bit down on where we should be. The rings have only done around 145 miles but given that the timing side is working well there is obviously a problem here, and combined with the oil leak around the top of the cylinder we are looking at a head gasket leak.

Looking at the plugs I wasn't surprised to find that they were both dark and wet. The last journey the bike had made finished with a few minutes riding at very slow speed through town - on the pilot jet. We will lean this out next time.

Riding back from the railway yesterday along the main road revealed that the bike will maintain 45 miles an hour at just under a quarter throttle - so until we are properly run-in we are not going to be able to do anything other than look at the carburettor slide cut away at the very most. We can adjust the pilot air again but we won't be able to examine the mixture from the main jet.

FH - weekly maintenance

 Just a little trip out this morning to pick up a part for the boiler from the Cromer. The bike is running very nicely and I managed to start it without the centre stand.

It's feeling a little bit squirmy so I decided to check the tyre pressures - the rear was a little bit down so we'll see what happens. 

I also put some tape and some marks to the throttle to help me set up the carburetion in the future.

This is the more traditional version of the Amal carburettor tuning chart showing us which elements of the carburettor affects tuning at various throttle openings:

Here is a more modern version, showing us a bit more detail and the overlap between the effect of the different elements:

Aside from practical adjustments like needle positions and the setting of the pilot jet, there are a few things we can change: 

• The main jet - available in a myriad of different sizes.
• The slide cut away - various sizes are available both larger and smaller.
• The needle. Most four strokes used the same needle, but there is a 'lean running' needle (part number 104) which is longer and thicker and clearly allows the engine to run with less fuel at higher RPM.

As the engine gets closer to being run in will be able to do some plug chops to determine the mixture at various throttle openings. At the moment, with only 138 miles on the clock what we can do is quite limited but I think we can look at perhaps the first half of the throttle opening range.

FH - back in action

 With the Square Four on the bench, the Huntmaster fixed and a trip for a job in Cromer in the offing it's time for a little bike ride. 

In preparation, I topped up the oil a couple of days ago as I had had the return system apart and expected the filter to be empty. I turned the engine over on the kickstarter with the plugs out in order to prove circulation before I used it again. 

After I'd finished my decorating job, I came back to the bike to find a little puddle under the rear chain case. I guessed there might be too much oil in the oil tank and so it proved: 

I filled the big syringe twice getting this back to an acceptable level. It's been off the road for a couple of weeks and obviously wet sumps! 

At the same time I adjusted the front brake and the head race bearings.

SQ4 - changing the oil

 It's high time Square Four had an oil and filter change, so with the oil return line repair complete on the Huntmaster the Square Four is back on the bench after a 10-minute run to warm the engine oil up. 

As usual it's an absolute pig to get the oil tank out but it's very easy to drain the tank and the sump - I have a new sump plate (well, it was new 10 years ago) with a drain bolt and magnet in the middle of it. I had something like 300 ml of oil out of the sump - I'm not sure whether that's unusual or not. 

I was surprised to find the sump strainer damaged - I think I'll get a new one from Draganfly. 

With the oil tank out I can degrease the area around the top of the box where the filler is - it's always quite mucky around here because it's very difficult to top the box up without getting grease everywhere.

The oil tank is also a very tight fit - it's always a struggle to get it out. I'm wondering if it's fouling the the frame tube, perhaps stuck between the frame tube and the gearbox plates.

I had the tank in the parts washer for 15 minutes washing the outside and the inside and was pleased to find very little sludge and no debris in the tank at all. There's obviously been some further washing of the engine through the detergent oil that I'm currently using as the cases appear very clean and the goo in the bottom of the tank and on the sump of drain plug is just like the dark grey substance you would get from the crankshaft sludge traps.

You can see one of the cams in this picture - the wear ridge is quite clear. I have a new camshaft ready to go in when I decide that I'm bored enough to rebuild the engine!

I filled in my maintenance spreadsheet but for the record the mileage is 4089 miles.

FH - chasing leaks

 This is the engine to oil filter pipe on leak test. No holes there!

However, this one is the oil filter to oil tank line:

So there's a nice leak there. The next step is to rework the oil line arrangement to the filter which I will do using a slightly different route between filter and tank since I think a contributing factor to this failure has been that the oil line has exceeded its minimum bend radius.

Charlie's Shed - chemical blacking

It's a fasteners that I've been making for the Model A are all turned from mild steel - there is no stainless on the bike at all. The plan is to use some gun blue or chemical blacking to reproduce the iron oxide finish from the original fasteners, called 'coslettising'. As an experiment I have used this product on the Huntmaster's oil filter bolt:

 Since I made it some years ago I have modified it to provide greater engagement of the thread. After turning I degreased it and suspended it in the cold blue for about 5 minutes followed by a rub over with linseed oil.