Cooling fins

Made from sheet metal since I could not find any large enoug cast iron cylinder to scavange.

The tricky part will be welding them to the cylinder.

Cylinder

After three days in a bucket with a mix of water and citric acid followed by a light brushing with a wire brush.

Now it's time for new cooling fins.

Notice the mark on the intake tube where the level of the ciric acid water has created a visible "border" in the rust and dirt. I still do not dare to try to open the intake nut. I also think it's treaded the wrong way, so to say.

Small Timing Gear Puller

To remove the small timing gear on the crankshaft I had to make a special  puller from a steering ball joint puller. Colonel Johan August Sandels is overseeing the procedure.

Engine identification

The engine was sold as a 250cc and the engine numbers might suggest that too. At least if one thinks /B stands for the cc.

Nothing seemed to add up and I could not figure out the meaning of the numbers and letters. When I measured the bore and stroke I came upp with approx 70x89. That would be 350cc I my book.

Trying to decode the serial number by the info on http://www.railtruck.org/jap_dating.htm I came up with the following:
I/S     I=350cc side valve, 70x90mm bore and stroke, S=1929
75163/B      75163=Serial number, B=Modified gear cover and exhaust valve lifter
H      H=Roller bearing pulley spindle
M     M=Crankcase without oil box.

Of the above everything seems OK until the letter M. At least there is something I would call an oil box.

But of cause the last paragraph on that page says "... this list is by no means infallible." 

Parts List

The parts list is not easy to find but I finally found it, or so I thought.

Comparing the engine I have got to the sectional drawing in the parts list I found, shows that the are not exactly the same. From the parts number found on my cam follower (6170/F) compared to the ones in the parts list (6176 & 6177), one could believe my engine is older? But if the years given for the parts list, 1919-1926, are correct I doubt my engine is older than that.

Fault 02 & 01

If I thought yesterdays find was a major fault, then todays find was humongous.

Both valves are crap. The one I managed to get loose, in the picture. The stem is completely worn out, the same of cause, goes for the valve guides.

The missing piece from the cam follower appeared today. Probably broken off when the valve seized or when someone tried to turn the crankshaft and the valve was stuck.

If anyone have an extra cam follower ( Parts no 6170/F ) feel free to contact me.


The one positive thing that I found out today was that the piston seems OK. No scratches and all three piston rings are loose.

The marks below the rings are caused by oil.

Fault 01

Started degreasing the engine, today. Opened the camshaft / rockerbox to make sure there was no water inside the engine.

Found a major fault: one of the rockers was broken. Unfortunately the broken off piece was missing, otherwice I would have tried to weld it back...

If anybody out there has a spare rocker, feel free to contact me.

J.A.Prestwich Industries

J.A.P might not need any further or deeper presentation, but anyway.

English engineering company and engine builder,  founded in 1895, defunct in 1965.

Made a wide range of SV and OHV engines, for motorcycles, stationary engines and cars. Both single cylinder av V-twin engines.

For me personally, I recognize the JAP brand mainly from their succes on the Speedway tracks.

N.U.T Motorcycles

There are a few sources on the internet about NUT Motorcycles, the name is derived from Newcastle Upon Tyne.

The short version is: From 1913 they competeds in motorcycle races and won the Junior TT at IOM. From 1914 they made motorcycles under the NUT name. Did not survive WW1, were declared bankrupt. Company (name) was bought and motorcycles were made from 1921 - 1933

Have not found much refernces to the NUT BTR (short for Board Track Racer from here on). Would like to hear from Trevor Hall and hear if he has any stories regarding the BTR's.

How it all started

For many years I've been drooling over pictures of old Board Track Racers as well as I allways wanted an old side valve engine to fondle with. Of cause there are a couple of them that I can pay a visit to at the local MC Collection whenever I want. That's just not the same.

The other week I was going through adds on the eBay and found this restoration project. An old JAP 250cc S V engine.

It was missing a lot of expensive parts as the Carb, the Magneto and the Oil Pump but I took a gamble that at least the internals would be possible to salvage and bought it more expensive than first planned, but what the heck.

When I later was scanning the internet for a parts list I stumbled over Trevor Hall's 600cc NUT Board Track Racer. From there on it was just to hang on and "go with the flow"

Rest of the few pictures of it can be found here.

The intention is NOT to build a replica of the above pictured racer. It is going to be my personal interpretation of a Board Track Racer, that will hopefully look a bit like the NUT