J.A.P. Twin Port 350cc OHV single cylinder engine from 1934 Sports Special.
Almost complete 1934 JAP OHV motorcycle engine that might have been built with some race specification. It’s a twin port cylinder head. So, it had sportier intentions than the single port. I mention that at the engine numbers read: IO (350cc) / D (1934), then the sequential number as shown in the pictures with /S. I understand that the “/S suggests that this engine was built as a Short Stroke Sports engine (or Special). Finally, if you look closely at the image of the engine number, you will see a STAR. The * = the engine has been specially prepared for something special like a speed attempt or just tuned to a rider’s needs.
I’m sure that there is a specialist on JAP motors out there who will confirm, or deny, this.
The engine: Overall, it’s in good condition although it has had some work done on it.
The engine case halves have matching numbers. So, they have remained as a pair since factory build.
The rocker mounts have been welded on. The rocker arms are there, but no springs. The cylinder head has good valves and valve seats. The valve guides are very clean. I have shown the valve seats in the images. There is one small fin broken on the head.
The fins on the barrels are good. The bore looks nice too. The dimension is approximately 71.8mm and , as you can see, the piston is fitted. The stamp on the top of the piston is 15-1810. The engine turns over with decent compression.
There are no timing cams inside the original JAP timing cover and there are no push rods or tubes.
The engine cases are in decent condition. Two of the barrel/ head stud mounts have been rebuilt. The head bolts down nice and tight and the threads are good.
The cast number inside the outer timing cover is NORAL 9633 and inside the timing cover, it reads 9517.
This is a very good start for a nice project. It has the makings of a decent engine and is much cheaper than a complete one. (IF you can get someone to part with one).
There is no doubt that this engine will need a bit more work to make a complete running engine.
If you have a vintage motorcycle project, the JAP engine is a popular choice. It’s sporty and looks great. Of course, JAP supplied their engines to many motorcycle manufacturers too such as OK Supreme and Montgomery.
Here’s your chance to get a J.A.P. Twin Port 350cc OHV single cylinder engine from 1934. A Sports Special.
International shipping available. Please ask.
Viewing: Please come and check it over before you buy. It is at PE28, near St Ives in Cambridgeshire.
Shipping: I usually ship to most destinations. If you don’t see a price, please ask. Thanks. International shipping available.
Collection: If you don’t want it shipped, I have plenty of space. If you can’t collect for a while, it’s not a problem. However, I will need to be paid very soon after the sale. Thanks.
Payment: Good old fashioned money on collection is preferred. I can accept payment through PayPal or by bank transfer as well.
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