Vintage Workshop
Services for Brough Superior motorcycles and their contemporaries

KTOR engine replica page


Just a brief specification of the 1927 KTOR JAP v-twin engine:

bore 85.7 mm
stroke 85.0 mm
capacity 981 cc
no of cylinders 2
cylinder angle 50 deg.
rated output 45 hp@4500rpm

What do we need to build this engine?

Starting at the bottom, a pair of crankcases. First of all we need a set of good castings. As this proved to be a problem, I have made a page exclusively dedicated to this topic.

Next, these castings will have to be machined. I found this is not an easy task if you want to achieve some accuracy. I say I have a deep respect for the brave men who did this successfully in the 1920's, with tool machines that were quite primitive by our modern standards!

Then, a crankshaft to revolve within the latter.
I will deal with that later.
And a pair of connecting rods (Carillos?) to attach the pistons to.

1/2006: I have now, after a few iterations, succeeded in persuading Carillo's to make me a pair of rods to my liking.

2/2007: I have spent much thought on how to make the flywheels. And I have spent even more thought on how to balance them.
If you know a thing or two about balancing crankshafts, please have a look at this page and let me know what you think of it!

03/2022: Another post-up: I have started to make the crankshaft during the last 12 months. A friend and keen mechanic in Austria came to help CNC machining it.

oh yes...pistons! I think I will use BSA Gold Star pistons. They have a crown height of 32.5mm plus a 10mm dome. To my knowledge the original ones have the same height, and a slightly higher dome, which is slightly smaller in diameter. The 3/4" gudgeon pin should be o.k.

A pair of cylinder barrels to give the pistons a good home.

I had already started to make my own pattern, but I tell you it is not easy to find a foundry who will make these castings. Usually they tell you to use half as many fins and make them a bit thicker....

But now (8/02), after much pleading from my side and a few problems, MFC (They are at ) have come up with these very nice KTOR barrel castings, thank you Mark and Mike!
I have now written a page about the barrel saga

And a pair of heads on top of them,
I have already ordered a pair of castings from MFC.
(They are at ) Meanwhile (9/02) I have taken delivery of a pair of head castings, and I am very pleased with them!
Click on the pic and see how I machine these!

Inside the timing case, we need some camshafts.
These came from John Holleren of Morgan fame. I have, of course, not tried them yet, but they look very good.
You can contact John at if you are lucky or give him a ring: +44-161-3303304.

And we need a lot of small stuff to actuate the valves,

some of which will hopefully be supplied by MFC (again).

Plus a number of small things: valve springs and collets, pushrods and their return springs, bearings, an inlet manifold, a breather valve, lots of nuts and bolts, and we will need an oil pump and a carburettor....
I am sure I have forgotten about a thing or two!
Yes, valves - we need to close those ungainly holes in the heads!
As usual, I looked at the readily available car engine valves and found a good one, but had to machine the spring cups and collets of course.

4/2004: Well, things are coming together slowly. The engine is still empty, but it is at least taking shape!

6/2004:  Now I have machined an inlet manifold. The casting was courtesy of Brough Superior Club.

10/2004: After looking out for a correct AMAL 6/022 carburettor for a long time I have decided to help myself. I have now started to build one out of a rather scruffy 6/024 (flange fitting) body...

12/2004: I have finally got around to finishing the overhead rockers I'd bought from MFC and to fit the bearings for this.

1/2005: Now I have made some progress with the valve actuating stuff: I have got the rockers and their bearings ready, and I have machined a set of cam followers

3/2005: I have, after a good two years of pestering a friend in England, obtained a pair of castings for the exhaust cooler. I found that machining these is not a job for a spare hour in the evening.

5/2007: I have recently got the castings for the rear coolers (which had been temporarily out of stock...) and have machined these. Nothing exciting, but I also made the missing threads on the front coolers which was a bit exciting!

6/2005: And I have at least started to make the valve lifter bits...

Well, that is all for the moment, but I will carry on!

Any kind of feedback to is appreciated
(sorry, this is not a clickable 'mailto:' hyperlink. If you want to write me, please type my address in your mailer. )

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