On 5/7/2020, Mark Wellard in Australia wrote:
"Sports And Classics offers a master cylinder cap for the Twin Cam. I ordered one, given that they are impossible to find. Although it fits, it is nothing like the original. First two photos are from Sports And Classics web site.


See pictures (with what's left of my original). I have since learned that people here have sent them back as incorrect but they still advertise and sell it. Apart from missing the center relief, the knurling is much coarser. I decided that it might be saved rather than sending it back. I spent a day making tools for my press and practicing on soup cans before trying to modify it, and the last picture shows the result". -- Mark



On 5/9/2020, Mark Wellard wrote:
"My M/C has an aluminum strap with the part number stamped (VBM3250)". Size of the number tag strap is 6-9/16” long and 1/4” wide


There is also a date inscription (20-2-59), probably date of manufacture. It corresponds with the production start date of the car. The inscription is made with a vibrating inscriber, similar to the numbers that SU put on the carburetor bodies.


On 5/9/2020, Mark Wellard wrote:
"Here are the details for modifying the incorrect master cylinder cap.
The first step is to remove the breather dome from under the cap (top right picture at top of page). This is held in place by a ring of stiff gasket material/card and is replaced when finished.

I started with a 22mm diameter bar, shaped at the end to mimic the curvature required in the finished product. I radiused the edge and in retrospect, should have made it a bit more domed. I center drilled this so that the center of the cap could be located. The reproduction has a breather hole with edges protruding underneath, which will help keep it centered in the drilled indentation of the tool. The bar is then cut off at a length corresponding to the final height of the cap – 16mm. This is shown on the far right of Figure 1.

I also made an internal support ring from plastic pipe (left side of Figure 1) to protect the sharp edge of the cap. This should be a snug fit to avoid distortion. Any material would work, it was a matter of what was at hand. This was long enough to support the cap, in case the press movement was sufficient to damage the height of the main cap and distort the edges. It protruded 2 mm beyond the cap when in place – this acts as a limit to the total movement while pressing the shape. When pressing, the total distance can also be judged from the amount of this ring remaining visible. Figure 2 shows the height of the center male shaper and the plastic support ring that sits inside the cap.

The female part of the tool utilized the base plate of a used spin-on oil filter (Figure 1, third from left). The threaded hole was turned to 24mm and because it has a dish (48mm diameter) that is close to the diameter of the cap, this can be placed to follow the slight dome of the existing shape. I think a flat plate with a 24mm hole would probably work just as well for this. The size of the hole will determine the radius of the dome. A larger difference in diameter from the lower male piece will give a smoother transition.

To press evenly on the cap, an old piece of outer bearing was placed on the outer flat of the filter base plate and a piece of flat plate (not shown) was put over this to take the force of the press.

After lining everything up (Figures 3 & 4), it is just a matter of applying pressure until the required movement is observed". -- MARK