Shakin' Strumpshaw Steam Rally

This years Strumpshaw Steam Rally provided the perfect opportunity for a decent ride, a lovely day out and the chance to shake out some more SQ4 problems.

Strumpshaw is a village in my home county of Norfolk located on the northern bank of the River Yare around 6 miles south-east of Norwich within the Broads National Park. The village lies a little distance from the river, on the slopes of Strumpshaw Hill, the highest area of land in the Norfolk Broads.

Strumpshaw Hall lies closer to the river, next to the Yarmouth & Norwich railway line from Norwich Thorpe to Yarmouth Vauxhall, first opened in 1844. It is the home of the Strumpshaw Hall Steam Museum, with a collection of traction engines, steam rollers, 100-ton working Beam Engines, a Narrow Gauge Railway, a 1930s Fairground, Mechanical Organs and much Memorabilia collected over many years by the Key family.

The Strumsphaw Steam Engine Rally is held each Spring Bank Holiday Weekend in the beautiful parkland grounds of Strumpshaw Hall. The rally hosts over 50 traction engines in steam and some 350 other exhibits including vintage tractors and heavy horses, stationery engines, fair organs, working demonstrations of steam and tractors, classic cars, trucks, fire engines and motorcycles.

It's the perfect spot for a ride out to meet the grandchildren, especially if the weather promises to be sunny.

The ride down quickly revealed that the steering problem had been fixed by proper adjustment of the wheel alignment, but that the chainguard was still a problem.

This KTM was the only bike to join me in the car park... It looks like all the other bikers registered their bikes as exhibits and got in for free:

The best part of the shakedown was the results from the carburetter temperature testing. After a 69 mile round trip with no misfire, and a 22 mile trip back at 55-60 mph we have these results, taken with the engine running in the yard and measured immediately upon arrival:

• 208°C on the fins near No.2 spark plug
• 131°C on the inlet manifold flange - near the offside carburetter stud
• 80°C on the carburetter flange, 1/2" from the 131°C measuring point but on the other side of the phenolic spacer. That's a 51°C differential across the spacer.
• 47°C on the float bowl.

Ambient was around 20°C for most of the trip. I measured the other cylinder head temperatures as well and added them to my chart with some previous tests:

Looking at these results, there is an issue around the focus of the thermometer. Normally I point the targeting laser on the plug body from about 15" away, which probably means we are measuring a 2" circle around the plug body; for Test 5 I aimed the laser at a fin and probably ended up measuring the plug insulator, explaining why the temperature is much higher. Consistency is the name of the game as any test engineer will tell you.

It appears that I haven't fixed the oil tank cap leak - maybe the gasket is not thick enough. I think it is better as the oil wasn't in the toolbox this time, but we have not solved that one yet!

And as the day drew to a close, I was left wondering how many of the Strumpshaw Ten Commandments might apply to riders of Square Fours...

Still Shaking

The summer is coming, the days are warming up and we need to get happy with the Square Four. Regular readers will know that it's overheated the carburetter and the chain is rubbing on the lower chain guard, but I have also noticed that the steering has been a little wayward - wayward in a 'I want to turn right' sort of way.

Having fitted the carburetter insulating gasket, it is time for another run out, this time to Aylsham M&S ostensibly to buy some rum. Initially we can see that the rear brake seems to be OK, while the front still needs some bedding in. The chain is still thrashing the chainguard.

Out in the country

Aylsham M&S, stopping for fuel

After a 12 mile run down to Aylsham we stopped for rum & fuel. I was delighted to find that I could comfortably put my hand on the carburetter float bowl - no boiling fuel here today and no misfire on the whole run. The oil pressure had been at a steady 50 psig running and about 25 psig idling so I'm delighted with that, and there doesn't appear to be any leaks either.

However, getting home there is oil all over the oil tank and the toolbox, again. This is a problem that has been recurring over a few years and I have always just cleaned it off, pretending it was down to the duff thread in the old oil tank. This time however, you will recall that have replaced the oil tank for one with a good thread, so that excuse has gone.

A short investigation reveals no seal in the tank cap... Did I really never notice that in the 6 years I have had this bike? Easily fixed fortunately.

Looking at the wheel alignment again, after the bearings were replaced in the winter, seems to be a good approach to isolating the steering problem. A few minutes with a straight board reveals a wayward rear wheel and a few minutes with the bike's toolkit it is easily fixed.

While I was under there, I had another look at the chain run and the lower chainguard. Yet another bit of judicious bending and we are done. Now we need another road test!

Dealing with Fuel Vaporisation

As I wrote a few days ago, whilst out on a shakedown run I had put about 6 miles under the wheels of the SQ4 when the misfire appeared. Power was really down and I had to drop to third on all the hills. Forgetting what the Four can be like in hot weather I was worrying about the ignition system, but managed to crack on home - I was overtaken by a military M20 at one point, as I could only manage 20 mph.

Back home, I put the bike back in the workshop and drained the oil tank, the sump and removed the filter. Sitting by the oil tank, I could hear the fuel boiling in the float chamber, and my Infra Red thermometer revealed that the float chamber was at 80°C and the carburetter body, near the cylinder hear flange was over 100°C - and remember, I had already spent 15 minutes draining the oil at this point.

I was clearly going to need the carburetter heat insulator that I bought a while back (in 2015!), which I had not fitted since I had the distributor the wrong way around - with the square 'condenser bulge' forward. This reduces the space available for the carburetter/spacer combination.

You'll see from the picture that there is very little room for the spacer before the carburetter hits the distributor, even with the bulge facing to the rear.

Pulling off the carburetter, it is immediately obvious that the existing, original studs barely have enough thread to allow a full nut to be used to retain the carburetter, so there is no chance of a spacer fitting in there as well:

Fortunately I have some 5/16" 303 stainless round bar knocking about, so we can make some longer studs. Here goes:

I've made them 1/4" long than stock. At this point I realised that whilst I have 5/16" BSW taps, I have no die. Now there will be a short pause...

RDG produced a suitable die, two days later:

Using the tailstock die holder made short work of the studs, but one of them has a CEI section which is a little longer than it wants to be I think:

Trying the carburetter in place, an unforeseen foul condition is revealed when the BiStarter hits one of the tank mounting bolts:

As expected, one of the studs is marginally too long in the CEI section:

There is still a few millimetres spare before the float bowl contacts the distributer:

So that's it. Stud adjusted, the carburetter goes on nicely with the 3 mm phenolic spacer, a paper gasket and some Threebond. The rear offside tank bolt has to go in afterwards.

Preliminary results show that it is pretty effective. Warming the bike up after the work, at rest, reveals the following temperature readings with the engine running:

• 162°C on the fins near No.2 spark plug
• 107°C on the inlet manifold flange - near the offside carburetter stud
• 39°C on the carburetter flange, 1/2" from the 107°C measuring point but on the other side of the phenolic spacer. That's a 68°C differential across the spacer.
• 22°C on the float bowl.

Whilst this looks encouraging, we must remember that this is a result of conducted and radiated energy - any convected heat is going upward towards the tank, not rearward toward the carburetter ; a 10 minute warm up is not a valid representation of 25 miles in a 25°C ambient at 70 mph, and we are not at full operating temperature yet.

But it's encouraging nonetheless.

Shaking Down the SQ4

A beautiful day and a bunch of spare time - the opportunity I have been waiting for to sort out the remaining SQ4 jobs and shake it down ready for the summer.

First off, check the oil in the primary case, which is all OK; the primary chain is suitably tight as well. Next, add 200 cc of SAE 30 to the fork leg we repaired, then tyre pressures, fuel and oil levels and then finally get out on it to warm it up for the oil change. A trip along the coast road on a hot day reveals that the rear chain is still rubbing on the lower guard, and after six miles of caravans & Bank Holiday tootlers the rear brake starts to feel unusual - a kind of vibration through the pedal. I was approaching Salthouse at the time, and I decided that this was only a shakedown run and that I ought to turn back. On a hot day, I reasoned, the oil will be hot enough to change after 12-13 miles.

Salthouse Village Green

That was when it all started to go wrong. I managed to follow a bus and two caravans out of Salthouse, and by the time I had put another mile under the wheels the misfire had appeared. Power was really down and I had to drop to third on all the hills. Forgetting what the Four can be like in hot weather I was worrying about the ignition system, but managed to crack on home - I was overtaken by a military M20 at one point, as I could only manage 20 mph. At least my newly refurbished speedo was working perfectly, as was the charging system. Oil pressure was over 50 psi all through the trip - dropping to 25 psi on tickover which I was very pleased with, but remember it is still running Penrite Shelsley Heavy 40W-70.

Back home, I put the bike back in the workshop and drained the oil tank, the sump and removed the filter. Sitting by the oil tank, I could hear the fuel boiling in the float chamber, and my Infra Red thermometer revealed that the float chamber was at 80°C and the carburetter body, near the cylinder head flange was over 100°C - and remember, I had already spent 15 minutes draining the oil at this point.

So, I must fit that Phenolic spacer and maybe a carburetter heat shield. There is probably enough room for about 4-6 mm of phenolic - I have some 3 mm Phenolic sheet at the minute. I may have to change the carburetter mounting studs but I think I will test out the spacer with half-nuts before I go to the bother of making new studs.

Looking briefly at the brakes, I probably have the rear nipped up too tight; the drum was smoking hot. The front had a bit more play when I got back and was working normally showing no signs of overheating. I will remove the rear wheel in a day or two.

So, after cleaning up the mess, I proceeded to remove the oil tank to exchange it for one with a good filler neck thread. I'll repair the old one in due course. All nice and tidy in there:

Look no oil tank

Fitting the new tank reminded me what a tight fit they are. My old tank had a relieved area under the frame tube, so I recreated this with a panel beater:

Next, having spent an hour winkling it into place, I remembered that the gearbox top nut has to be removed to get enough clearance to allow the bottom mount back into place. All fixed and back together now.

This year I will be mostly using... Penrite Shelsley Medium 25W/70:

Boots

Riding my W/NG around the yard the other day, wearing completely inappropriate clothing was quite enjoyable - sun out, gloves off etc. Getting home I noticed a bit of damage to the elastic sides on my old RM Williams boots:

I realized they were chafing on the end of the clutch cable end, which has no boot. Since this is a 1942 bike, it should have a rubber boot over the whole clutch arm:

Here's one I bought on eBay:

These are not too tricky to fit, but fitting will surely let you know whether the boot you have is a good quality one by splitting when you draw it back over the clutch arm. First, remove the clutch cable and slip the boot over the arm. Then, push the small end of the open end of the arm, exposing the slot where the cable fits like this:

Put the cable nipple back in the slot, and you can winkle the rubber back over the nipple, covering it completely: