Villiers stationairy engine

[cardan]

I'm no expert, but I think the XII-C was introduced in about 1931, and this one might be c1933? No doubt 33d6 can be more authoritative. As i mentioned above, start dates are useful, but it's more interesting to know for how long a particular style of engine was built and used... Always interesting to see an engine like this in its original bike, so that the bike dates the engine rather than vice-versa.

Leon

[33d6]

Can’t help with the second Mk XII-C engine. My information is based on records of unique Australian motorcycles, not all motorcycle makes. In general most of these minor makes started to appear here in the mid thirties and quickly disappeared when war was declared. None survived WWII. Numbers start around the 6500  and end around 11000 in 1940.
Calculating the Villiers engine approximate year of production from these records was a serendipitous by product of other efforts. It was not my intention nor as I keep saying, does it serve any practical purpose.

As far as your engine stands it is what in my apprenticeship days we called a ‘short’ engine. Not a complete unit and would be used as an exchange, refitting all the essential fuel, ignition and drive components already present from the receiving machine. On its own it is only one sub assembly of a Villiers power unit.

Curiously, the Mk XII-C cast iron piston is well catered for. F W Thornton of Shrewsbury list all sizes and oversizes on their website. It’s only the favoured alloy versions that are hard to find. It seems I’m not the only one to choose alloy pistons over cast iron. Its not a genius decision.

[Albion EJ]

Thanks again!

Sorry I misunderstood the preference of an alloy piston compared to a cast iron.

What is in your view the biggest advantage of having an alloy?

Indeed I also have cast iron ones found only so far.

[33d6]

In broad terms an alloy Villiers piston is 1/3 the weight of its cast iron equivalent. Thus the engine runs more smoothly as there is so much less weight moving up and down the cylinder. Further to this it takes much less power to move the lighter piston in the same fashion so the extra power required to move the heavy cast iron piston is now available for the rider to take advantage of. Finally the alloy piston disperses heat better than cast iron so the engine can be worked a little harder with no detriment.

So the upshot is the same engine with an alloy piston runs more smoothly, revs more willingly, is a little nippier and stays a little cooler.

Cast iron has its virtues. Given care a cast iron piston will last indefinitely running in a cast iron cylinder. It is easy to work and requires little if any heat treatment. It is also cheap. In some circumstances an operator may value these virtues above those offered by an alloy piston.

[cardan]

There seem to be a lot of GY-prefix engines used in little Francis Barnetts in the 1930s, like this one: https://cars.bonhams.com/auction/29728/lot/229/1933-francis-barnett-148cc-lapwing-27-frame-no-c27176-engine-no-gy-4934/

Some of them have a GYF prefix. What does the 'F' mean, and was there a serial number reset to go along with it?

Leon

[Albion EJ]

Another nice example

https://andybuysbikes.com/bikeshtml/6915cve.html#

[33d6]

Villiers would add an extra letter to the engine prefix for various reasons, not all of which I yet know but no matter what the underlying engine remains the same.
I do know the extra ‘F’ refers to FIXED ignition. Previously Villiers had clamped the magneto backplate onto the protruding main bearing bush. Slackening off the clamping screw allowed moving the backing plate back and forth to get the ignition timing just so. Villiers even fitted an advance and retard lever to the backplate to facilitate this. It didn’t work. Getting the clamping force just right, loose enough to move but tight enough to stay put otherwise was nigh impossible. Some factories fitted some sort of device to hold the lever in place but these have mostly disappeared over the years.
The idea of slackening off the clamping screw to tweak the ignition just so remains a good one, just make sure you tighten it up again afterwards.
In the end Villiers not only dropped the idea but went further and mounted the backplate permanently in a fixed position, hence the additional ‘F’.
This came late in the XII-C’s life. The earliest engine number I have is GYF 10421, first registered in May 1939.

[cardan]

Thanks 33d6, very interesting. I wonder if Villiers reset their numbering for the GYF engines, if only because of this bike that is claimed to have engine number GYF2612: https://www.handh.co.uk/auction/lot/61-1937-francis-barnett-plover-41/?lot=10584&sd=1

That said, I only take numbers seriously when I have seen them for myself! Plenty of scope for mis-reading or mis-transcribing.

Also difficult is engine swaps: I assume the '1939' Andy Tiernan bike could easily have an earlier engine fitted at some time?

Anyway, my interest in these little 147/148cc engines come mostly trying to understand better the little Australian bikes of the 1920s, mostly Elliotts here in SA and Waratahs in NSW. Engines are now under control, but frame numbers are problematic. Waratah had mostly just Sun numbers, having been built (I believe) in the UK, whereas Elliott built up their own frames and stamped their own numbers, sometimes very badly! But after half a century of cobbling together cheap and cheerful little vintage bikes its a bit hard to make sense of some of them. Others with established provenance make perfect sense!

Cheers

Leon

[33d6]

As you remark Leon, placing trust in auction house puffery is moving on to shaky ground. Even the auction houses warn you against it.
So far as engine swaps are concerned a major virtue of Villiers engine was they didn’t change from year to year so you could safely exchange engines without worry plus of course for years Villiers powered bikes were so poorly regarded that it made more sense to replace a worn out engine with another less worn secondhand one than actually spend money refurbishing one. After donkeys years of these old bangers being mauled about its bizarre that we should expect the numbers to match up.
As you say, it’s only the ones with an established provenance that make sense. Provenance is all.