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Motor Identification.

jt48

Registered
I have had this motor for sometime. Or at least it was a motor at one point. It was converted to an air compressor a long time ago. I was wondering if anyone would know what it was originally. There are no markings on it anywhere that I can see. My friend saved it from the dump and gave it to me so no history that way.



 

SteamfanMN

Registered
What's that on the left of the crankcase? A filler cup of some sorts? Another sort of interesting thing to me at least is that it has a internal cam system where a majority have a external cam chest. Not sure what it is but I'm looking and I like it!

---------- Post added at 10:08 PM ---------- Previous post was at 09:38 PM ----------

A part of me wants to say Royal Enfield? :shrug: They seem to have a very close similarity. The closest appears to be a 1926 or so. Hope this helps!
 

RDub

Registered
Last Subscription Date
10/26/2014
can we get more photos?

---------- Post added at 06:12 AM ---------- Previous post was at 05:40 AM ----------

sorry just noticed them
 

RDub

Registered
Last Subscription Date
10/26/2014
It is a JAP. I'm having troubles uploading right now http://www.barnstormers.co.nz/1327/1933-j-a-p-engine-information/
Not sure if I did this right.

---------- Post added at 08:52 AM ---------- Previous post was at 08:44 AM ----------

Okay seems to be working. Really cool motor!! The advert is from 1917. It shows threaded exhaust bungs. I believe by '24 most of the motors had changed. I think your motor is of the newer style. At least the valves are still there. Looks like you have good starting point. I do not understand the cup on the backside. Is it an oil fill or filler cup as previously mentioned. Thanks for sharing
 

eddie bedwell

Registered
Hi RDub,
I believe you have identified it.
Alas, it looks like the cam case has been machined off the crankcase for the new air compressor application.
Looks like pieces of round have been fitted to a possible de-compression plate under the valve stems.
Nice find and start to a project.
Cheers,
Eddie B.
 

jt48

Registered
Thanks guys, it very well could be a J.A.P. Also as Eddie said, the case looks like it has been machined. Frost plugs put in the holes where the cam series would have run.
 

Peter Short

Registered
Last Subscription Date
11/09/2017
It is a JAP.
Maybe it is.....but there is no evidence so far.

There are many differences between the JAP photo and the mystery engine.

For example, where is the large JAP logo cast into the crankcase?
 

RDub

Registered
Last Subscription Date
10/26/2014
Peter, Although Mr. Prestwich was very good at making sure his name was on his motors. Not all of them did. The reason all of them were in the catalog is that was a JAP catalog. If the customer had requested special castings w/out the name (and they were willing to pay) it could have been done. This is exactly what happened to Perry Mack. The California was cast with Deluxe in the bottom of the case. That motor was clearly documented as a PEM. Now, It is possible that this motor is not J.A.P. I have been known to be wrong. See the thread by Ryan Newman . . ."what is this motorcycle?"
That being said, This motor should have some numbers to help identify it. Flywheel casting numbers at a minimum. That will have to wait until and if the motor gets torn down.

I also thought it was interesting how the shafts had been cut and plugged. I think there are more plugs then there were shafts?:shrug: Not sure on that. . . Any JAP experts care to comment on that?

---------- Post added at 11:10 PM ---------- Previous post was at 11:00 PM ----------

Just went back and compared this to some other things I have. I believe (speculation on my part) this case hase been machined. Look at the circular tooling marks across the cam chest and near the outside perimeter of the case. Possibly during the machining of the cam chest the JAP was also removed. It is hard to tell from the perspective in the advertisement but it appears the logo was small and on the outside. If this is the case tho' it seems there would be some witness to the letters or a boss? That being said. I still believe this to be a Prestwich.
 

RDub

Registered
Last Subscription Date
10/26/2014
Steamfan, had mentioned the motor looks like a Royal Enfield. It sure does! But, In the pictures here of two enfields that are of the same era as this motor they are different from the motor in question only slightly. Count cooling fins.
I also have this picture of a JAP used in a Morgan. Now I understand this is a newer motor and not F headed but look at the crankcase. I assure you this is JAP without question. (the one from the Morgan)
New Imperial also had a V-twin in '25 that didn't have JAP in the crankcase or on the timing cover. It is beyond doubt that it was supplied by JAP this way. I do not have a way to scan this into the computer. I bet that information is easy to verify by Googling.
I have the ability to be wrong and have shown it to be true. However, until shown evidence to the contrary, "it is a JAP"
 

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