Vintage Workshop
Services for Brough Superior motorcycles and their contemporaries

KTOR overhead rockers, last update: 14-01-2004

One problem with the KTO rockers is the roller bearing on the timing side. Originally the rockers bear on a set of loose rollers here, which wears out the shaft relatively quickly, as the rollers are "treading on the spot", i.e. they do only a fraction of a revolution at each valve stroke. Besides, the outer bearing ring is unobtainable and would have to be specially made.

A (Morgan-) proven modification for this is to use a readily obtainable needle bearing (Torrington B-166) which fits exactly into the "dog ears" .

As this has a thin-walled pressed steel outer shroud, it needs to be fitted quite carefully. I have, following the advice given in the Torrington catalogue, made a special tool to pull the outer ring into the bore.

The important thing is that the face which puts the pressure on the outer ring is slightly undercut, so that no pressure is applied onto the inner edge which is holding the needles. This worked very nicely.

Now the idea is that a corresponding inner ring is fitted onto the rocker shaft using a split collet that is inserted between the inner ring (which is 3/4" inner dia.) and the shaft (9/16" dia.)

The part number of the ring is Torrington IR-128, but unfortunately this ring is too wide (1/2" instead of 3/8") and there seems no other ring available.

I found these can be shortened using a tungsten bit tool, but you cannot just chuck them as they will slip under the cutting forces. To hold them, I made a small steel bush having a step on the outside ( to keep the bush from slipping into the chuck) and inside (to keep the ring from disappearing in the bush).

This worked quite well.

Unfortunately it seems I forgot to make any pictures of making the split collets, I cannot even find the drawings for them - sorry for that!

Now, this is the ring in the bearing. (no, bugger, I have not shortened it too much, it has just dropped in a bit too far on the pic!)

In the background you can see the other bearing, which is a more or less standard SKF RLS4-ZZ. Well the ZZ stands for the metal covers on both sides which I think are an advantage over a normal open bearing.

I had to make a set of nuts and locknuts for he drive side end, which was a pain, as for some reason the (hardened!) threads on the rocker ends were slightly oversize. Which meant screw-cutting 8 nuts on the lathe!

Also the rockers wanted some little machining, which meant to make up yet another jig.

Now, I polished the rockers and had them plated.

Which meant masking off the threads and bearing fits.

I used plastic "nuts" for the threads and a snugly fitting piece of silicone hose for the bearing portion..

This worked very well, but unfortunately, upon collecting them, I found that the nickel had a tendency to flake off.

They will have to go back to the platers, shiny as they are...

I also needed the bearing covers. 16 of them. If you have ever cut these from a sheet you will probably not do it again.

I had them laser cut, and I used stainless steel, as I did not feel like messing around with the plater's, being told that flaking nickel is normal or something of that kind.

The grease nipple lug was turned from stainless bar and silver soldered. Yes, it takes a while to clean it up, but now they are fit-and-forget I hope.

I would have loved to present a picture of the total assembly, but I have still got a problem to solve with the valve springs.

The ones I have got do not look too well made, and I'd like to have them ball-peened in order to enhance their fatigue strength, due to the disaster I had with the springs on my 680 ohv...

Meanwhile I have only got a picture of a preliminary assembly, with the covers unpolished and the rocker unplated I am afraid.

By the way, something does not look quite right here, does it?

I found that the sharp laser-cut edge needs to be blended in a little; it is a trifle but they look much better now!

To be continued....



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