Design and Prototype-Brian Mackenzie

Design and Prototype-Brian Mackenzie Velocette engine work and machining

New electric van means new floor. Tried hexboard for the first time. Ideal for the job. Middle seam means all out of a s...
27/07/2026

New electric van means new floor. Tried hexboard for the first time. Ideal for the job. Middle seam means all out of a single sheet.

Made a simple swage block out of hex bar to crimp 17mm OD braided oil hose. This is too big for the usual petrol pipe fi...
19/07/2026

Made a simple swage block out of hex bar to crimp 17mm OD braided oil hose. This is too big for the usual petrol pipe fittings. The ferrules are 20mm OD so I bored 17mm.
Worked a treat in the bench vise.

Now I’ve got the squish head working it’s time to balance the crank to the MSS piston. I was going to leave it until win...
11/07/2026

Now I’ve got the squish head working it’s time to balance the crank to the MSS piston. I was going to leave it until winter but I couldn’t stand the vibes any longer, very un-Velo. I’ve got a client balancing job on Wed so I’ll do them both together.

Engine strip down tip. If you find the barrel is stuck in the crankcase, don’t fall into the trap of risking fin breakag...
10/07/2026

Engine strip down tip. If you find the barrel is stuck in the crankcase, don’t fall into the trap of risking fin breakage by levering up.
Instead pop two of the studs back in loosely and using a large (Whitworth 😃) spanner twist the barrel too and fro, to break the seal. If you lever gently up from the INSIDE of the bottom fin on the front, whilst twisting, the barrel will lift easily.

Made some vintage BSA suspension components. Material was EN24T which is tough stuff. I had to use tips for stainless to...
09/07/2026

Made some vintage BSA suspension components. Material was EN24T which is tough stuff. I had to use tips for stainless to get a decent finish and re-grind my drills to 10deg for hard materials.
Boring 33mm dia actually got the headstock warm for the first time.

Hot work day. Shop-made drift for the new seats, with interchangeable heads for different sizes. Valve guide drift from ...
02/07/2026

Hot work day. Shop-made drift for the new seats, with interchangeable heads for different sizes. Valve guide drift from EN24T, flame hardened to stop it rounding over.
Seats and guides frozen overnight and head heated to 160deg, soaked for an hour.
With everything laid out on the bench it was time to drop the flag. Fortunately the commercial seats were 4-5 thou interference and the shop-made Colsibro guides machined for a 2 thou interference.
For once, it all went to plan and several hours preparation and tool making was time well spent.
Just got to let it cool before res@i g the guides to final size and cleaning up the valves.

29/06/2026

Roughing out for some custom valve guides in Colsibro. Beautiful stuff or what. That swarf is probably worth a quid 😃
The reason I make them to suit is that, in this case, the apertures in the head are 2 thou’ different and the interference is 2 thou.

The 1939 MAC I have just sleeved, running-in in the countryside near Tokyo. Perhaps I should open a branch there. 😃. Saf...
29/06/2026

The 1939 MAC I have just sleeved, running-in in the countryside near Tokyo. Perhaps I should open a branch there. 😃. Safe riding Masaya.

Brazed up a simple pointer to use for setting the timing. Saves finding top dead centre every time. I’ll be using it wit...
28/06/2026

Brazed up a simple pointer to use for setting the timing. Saves finding top dead centre every time. I’ll be using it with a strobe.

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