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Identify these bikes! / Re: Strange JAP cylinder
« Last post by cardan on Today at 04:41:55 AM »
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
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Identify these bikes! / Re: Strange JAP cylinder
« Last post by cardan on December 14, 2025, 01:32:45 AM »
Hi Ralf,

The really unusual thing about your engine is that it doesn't have an "oil box" on the crankcase underneath the timing chest. JAP introduced the oil box in 1914 - it uses crankcase pressure and flapper valves to distribute oil around the engine. All large JAP engines after 1914 used the oil box, but not yours. Yet it has the "sports" style cylinder with the separate spark plug hole.

Without an oil box, my guess would be that the engine was for an industrial application (a trolley towing luggage on a railway platform, a concrete mixer, or whatever), but it could also have been supplied to order as a "cheap" motorcycle engine? Sorry I can't be more definitive.

Cheers

Leon
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Identify these bikes! / Re: Strange JAP cylinder
« Last post by Ralf89 on December 13, 2025, 08:44:01 PM »
Hello
Many thanks for your response!
You are absolutely right- I am from Austria and I found this engine also here in Austria. As far as I know the 550cc engines where very popular in Germany and maybe also here in Austria. According to my research the "Y" on SV engines stands for the cheaper "Roadster" or "Standard" version. They has smaller valves and no rotary breather than the sporty SV K and U engines.
So far so good. But my problem is as mentioned before the fact, that normally the KY and LY engines has the sparkplug located directly on the intake valve cap, but my engine has a seperate hole for the sparkplug like the sporty K and U SV engines. But with the small valves and tiny cooling fins.
Very confusing....
Maybe it is really a industrial engine...
Thank you.
Regards
Ralf
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Identify these bikes! / Re: Strange JAP cylinder
« Last post by cardan on December 13, 2025, 08:57:08 AM »
Hi Ralf,

JAP made a lot of engines, and as Rex points out not all of them went into motorcycles. By 1927, when your engine was built, there weren't many makers using the 500/550/600cc side valve singles. Possibly your engine came from a continental maker, rather than the UK.

Anyway, I don't really understand LY/I as a JAP prefix. The L is OK (85.7 bore) but Clew says that Y means twin port head, in which case I'd expect Y to be always accompanied by O (eg LOY) meaning ohv. Not to worry. LY probably means 550 sv. I after the / is unambiguously 1927.

Here are some sv engines form the 1927 JAP catalogue. Do either of them look like yours? Your photos don't show this side...

Cheers

Leon
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Identify these bikes! / Re: Strange JAP cylinder
« Last post by R on December 12, 2025, 09:46:04 PM »
Ditto.

Rob Saward has written a little booklet about dating JAP engines,
additional to all the pneumatic palava, as research into aussie built versions.
He'd be the chap to ask, although his health may not assist here.
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Identify these bikes! / Re: Strange JAP cylinder
« Last post by Rex on December 07, 2025, 12:58:56 PM »
I nothing less than nothing about JAP engines other than they made many more industrial and stationary engines than bike engines, so maybe it's off something like that?
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Identify these bikes! / Strange JAP cylinder
« Last post by Ralf89 on December 07, 2025, 07:16:51 AM »
Hi,
Has anyone every seen such a Roadster cylinder with seperate sparkplug hole like the SV sports engines K and U?
Furthermore this cylinder has very tiny but many cooling fins.
This cylinder was mounted on a 550cc Roadster engine from 1927 ( LY/I ). It has the original bore of 85,7mm and a stroke of 95mm, so it is a real 550 roadster barrel. But I haven't ever seen a roadster barrel with seperate sparkplug hole and such tiny fins.
In the pictures you can see this cylinder compared to a 500 roadster KY/W
Thanks
Regards
Ralf
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British Bikes / Re: Villiers battery charging system ?
« Last post by R on December 03, 2025, 10:00:40 PM »
Yes, I would regard a working (and visible) brake light in particular as essential in modern traffic.

Funny you should mention replica lamps. I've just taken delivery of several, and apart from no Lucas logos
or numbering they seem almost indistinguishable from the real thing. Sure beats an empty space, at least ...
Even the paintwork has improved lately ? 
We will see if they still work in 70+ years ?!
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British Bikes / Re: Villiers battery charging system ?
« Last post by Vreagh on December 02, 2025, 10:53:32 AM »
He may of fitted a cheap chinese reg/rectifier, and that headlight looks like an indian Lucas with a LED bulb to be that bright. I've done similar with my 1929 FB with no lighting coils. I fitted a 45 watt dynamo and made a 12v regulator for it, coupled with 12v bulbs all round, even a brake light. Not concours or to spec but very rideable.
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British Bikes / Re: Villiers battery charging system ?
« Last post by R on December 02, 2025, 09:10:15 AM »
So where does this wee beastie get all the juice to power that big headlamp.
Not knowing lil RE's in the slightest ...

https://www.ebay.co.uk/itm/146989249719

Edit. Specs say it has Villiers direct (AC) lighting
And were new for 1933 ?


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