I bought a J.A.P engine from ebay.co.uk this month . i recived it for a couple of days ago ..I have started to mount it down for repaint. i will like to know witch model this is. The ID plate at the engine are gone.
And where can i buy parts for it? I need some different parts before i can start it . as piston rings. maybe a new piston, gaskets and maybe some carburetor parts since the petrol seems to owerflow right trough.
There is a Zenith 24T2 Carburetor at it.
I´m new here so if you know anything please mail me at anders25@online.no
There is reference to J.A.P. engines in a couple of my small engines service manuals but not the model in your pictures. The initials stand for J.A. Prestwich Industries Ltd., Northumberland Park, Tottenam, London N17, England. The company doesn't show up in my eighth edition of small engines service manual printed in 1966 so assume it went out of business around that time.
Maybe someone from England can advise further.
Last edited: Mar 28, 2006Discovered an air shroud that sold on ebay a couple of weeks ago that looks like the one on your engine. The seller indicated that it was a model 5 and you can make that out stamped somewhere on the shroud in one of the pictures shown.
I bought a J.A.P engine from ebay.co.uk this month . i recived it for a couple of days ago ..I have started to mount it down for repaint. i will like to know witch model this is. The ID plate at the engine are gone.
And where can i buy parts for it? I need some different parts before i can start it . as piston rings. maybe a new piston, gaskets and maybe some carburetor parts since the petrol seems to owerflow right trough.
There is a Zenith 24T2 Carburetor at it.
JAP goes back to the 1920s and 1930's, they made big motorcycle V-twins and small two stroke engines. The industrial engine side was started after WWII and they made quite a range of engines, the largest being the Model 55 which was essemtially 2 X Model 5 engines on a common crankcase and an extra small flywheel at the other end of the crank.
When JAP failed as a company, they were bought by Villiers, who are still around today. However, most of the JAP spares are long gone now.
The 24T2 carb picture is on our website:
I have a JAP engine handbook which gives service information like tappet clearances and ignition timing etc etc if you need more information.
(The company name was short for J.A.Prestwich, not Prestwick)
Thanks for pointing out the incorrect spelling of the name. It was misprinted in my service manual. I see it was corrected in a subsequent edition. I've corrected the error in my previous post.
Your Jap engine looks to be a Model 5. I have one mounted on an ex. Air Ministry wartime compressor set, which I believe was used for starting aircraft engines(?)
As for spares, second-hand stuff is available from auto-jumbles here in the UK if you know someone here to get it for you, or for new/old stock parts try Meetens Industrial engines Ltd.
They have a website at www.meetens.com, I found them most helpful for parts for a Villiers engine on a mower.(They also stock Villiers,Jap,BSA and Kohler parts).
Best of luck with your engine,
Regards Richard.
Thanks for pointing out the incorrect spelling of the name. It was misprinted in my service manual. I see it was corrected in a subsequent edition. I've corrected the error in my previous post.
It gets misspelt over here too Bill, don't worry about it! )
We have an original JAP manual for the 4/2, 4/3, 5 and 6, and while we can't offer copying or scans due to time pressures, we can extract information from the book and pass it on.
The 4/2 was 245cc, 2.4bhp @ 2400rpm, Wico Mag A576BZ.
The 4/3 was 288cc, 3.5bhp @ 2400rpm, Wico Mag CJ936
The Model 5 was 412cc, 4.5bhp @ 2200rpm, Wico Mag CJ936
The Model 6 was 588cc, 5.5bhp @ 1800rpm, Wico Mag CJ936
The Model 55 was 824cc, 8bhp @ 2000rpm, Wico Mag.
Another good book to get hold of is "The JAP Engine" by A.C.Fenner, published by Arthur Pearson Ltd in the 1950's. This book covers the motorcycle and industrial engines, including the racing V-twins as used on dirt-track bikes etc.