A very different J.A.P. engine, POZ/R 11254/S 1935 timing-side casing – maybe an original crank inside?? The pushrod tubes are split at the cylinder-height, as is visible here. Their distance apart is closer than normal and the top half is joined fast to the bottom half of the UFO-dish, as is clearly seen above. The crankcases appear to be standard… Time will tell!
The drive-side casing has been ‘rather’ modified in two noticeable areas: Firstly the integrated dynamo mounting-ring and then the interesting removable drive-side bearing?? The shape at the top of the casing under the barrel is also very different to the standard flat sides of an original JAP.
OK, the barrel is also very non-standard alloy with big fins and fits the shape of the crankcase nicely. The head itself seems not (as far as I can see up to now) to have been altered or replaced, so a standard cast-iron, twin port J.A.P. head. THEN on top the UFO Valve enclosure and their own rocker arrangement… The UFO itself is made at least partly of 3mm brass!
This is what the UFO looks like inside, before I remove the Rocker assembly. I’m not sure if any of the standard valve-operating gear actually fits anymore, but we will see, said the blind man! This is quite different to standard practice!
Here inside with the rocker assembly removed
The ‘lower half’ of the UFO is fitted in such a way that it is not easily removed: AFTER placing it on the head, there’re 2 sleeves pressed into the bored-out valve-guide holes and then brazed in place on the dish, mating it with the head. This is then Cleaned off flat and another sleeve with a step is pressed into that first one and the valve guide itself then afterwards (see the pic above, where the sleeve and guide have been strategically placed for the photo! So, to remove the dish, the guides + their sleeves have to be pressed out and the top area ground down on the outermost one after the first are removed – to break the seal with the head – then that presumably allows that one to be pressed out to separate the head from the dish. Phew!
I shall not be doing any of that. The head will be gently blasted and new guides fitted with the rest of the parts that came out of it. The head, barrel, pushrods and pushrod-tubes all line up only with one another and so fitting another standard head with standard tubes and barrel will be impossible and a complete barrell-upwards swap will be needed to get it back to normal JAP spec.
I find it interesting to have a ‘different’ engine, anyway, despite the challenges of finding parts should anything go wrong, so I intend eventually to have a standard setup ‘just in case’.
Here from inside the combustion chamber, with the last sleeve easily visible after removing the one around the valve-guide itself. That is the one holding the lower dish of the UFO on on the topside.
Here the width of the head itself, being considerably less than the top end of the finning on the barrel…
The (Bosch) dynamo is of a strange diameter and the Bosch people here seem to be at a loss to repair/restore it to working condition and the magneto is also VERY strange and was obviously ‘modified to fit’. Carburettor is missing, soon to be replaced with a NOS unit, without an appropriate float chamber as yet.