classic motorcycle forum

Interesting. Does this mean you can't just swap flywheels between different models of engines,
or that you can't even swap the whole kit & caboodle between engines ?

I merely pondered swapping from a 2 coil set to a 6 coil set, without any serious intent...

Hi Ralf,

I'm sure you're right. The "Y" in this context probably means "no oil box" = "cheaper version". I had a look through the Show Issues of the Motor Cycle in 1927-28, and very few British makers offered sv JAP singles in this era. When they were "serious" bikes, like to 500cc sv HRD, they used engines with oil boxes. I couldn't find a single illustration of a 500+cc JAP single engine without an oil box, but that doesn't mean there weren't any, instead that they were cheaper models, and who wants to see an illustration of a cheap model!!

In the VMMC machine register I found a 1929 Sun with a KY/S engine, here's an loose LY/D (1934) engine https://cars.bonhams.com/auction/23600/lot/131/a-1934-jap-550cc-sidevalve-motorcycle-engine/ , but overall the big oil-box-less sv JAP singles were not common in British bikes.

Fun to learn something new! Do you have a plan for the engine?

Cheers

Leon

We'll have to agree to disagree on that one Rex. Sadly I think the British motorcycle industry dropped the ball badly with their lightweights in the 50s & 60's. I own nothing but British but only of the late 20's with some 30's stuff and when I compare them to models made by the same factories 20 -30 years later I find they're just making an updated version of the same thing with little improvement in economy, performance or braking. Definitely better in suspension related areas but not much else. The expression polishing a t**d comes to mind. Fresh ideas and a fresh approach were needed and it didn't happen.
Although I'm no fan of their odd combined kickstart/gear lever setup I have to admit the Jawa/CZ's of the same period are markedly better and and German two-strokes of the period were magnificent. It's just a pity that their motorcycle industry collapsed when the German economy reached take off point and the average citizen could afford a car leaving two-wheelers behind. As for TWN, a friend had a TWN Contessa scooter and it had no problem maintaining station with the 350 Ariel I was riding at the time. And it had electric start when such a thing was quite exotic.
I enjoy playing with my Villiers stuff but I have no illusions that it could've been better.

 
   

For various reasons I haven't been looking here much lately so have come in at the end of the above chatter. I gather from what has been said on previous occasions that you are writing about your 9D powered Waratah/Excelsior R. If so you don't seem to have a relevant Villiers manual which does make it a little tricky. I'll start with the first question and try to work through them all.
Of course there's no voltage control. Can you think of any British bike of the time that DID have voltage control on an AC system? I think Triumph were more or less the first major factory to fit alternators. They had the same lack of voltage control and those following weren't much better. I remember much unhappiness about batteries boiling dry and other woes in the early years of it all and a distinct lack of enthusiasm about the infamous multi-terminal Lucas combined ignition and lighting switch. What was it? the PS or PSR8? It's no consolation but Villiers were no more and no less ghastly than much more expensive machinery. Let's face it post-war British motorcycle electrics were never world leaders.
Essentially the factories fitted only the one size 6Volt battery, I don't think they had much option. I think it was the only one available and it seems as it acted as some sort of electrical buffer in these systems. They all seemed to revert to the old three brush dynamo idea of a daylight charging rate and a night time head lights on charging rate which never worked particularly well. I'm no electrician, maybe there was some sort of secret to it.
Next, there were two lighting systems used on the 9D. From memory, 18 watt or 24 watt systems. The lower wattage having both fewer coils and smaller magnets. You appear to have the lower wattage cheaper system fitted. Perhaps this was one of the ways the factory differentiated between an Excelsior or a Waratah. I don't know. Whatever, they are both standard Villiers systems of their day but you have to work to the limitations of each.
As for light switches Villiers supplied a relevant light switch for whatever lighting system you used, rectified lighting with a battery or directly off the lighting coils. The four position switch was late on the scene, well after your wee bike. Before Villiers provided this switch to change between steady battery lighting for town use and 'direct' lighting for country running the knowing rider wired in an extra dip switch and used that to flick between the two systems. Eventually it dawned on Villiers that they could add the dip- switch trick to their standard switch and sell it as a standard function but as your bike predates this you could use the extra dip switch concept as being absolutely correct for the time. Just remember that LED's probably wouldn't like the change to direct lighting too much. They're rather keen on a steady current without erratic swings. It's an arrangement for old fashioned bulbs only.
Finally I'm in complete agreement with the idea of a brake/stop light on any bike. I have absolutely no faith in any following traffic.
Anything else I need to cover?   

I had a random thought about this engine. /I usually means 1927, but it can also mean 1947. Speedway engines aside, JAP didn't build many motorcycle engine post-WW2. I don't think it's really likely, but could this be a 1947 engine used in a European bike? All sorts of things were being exported from the UK after the war.

Leon