Design and Prototype-Brian Mackenzie

Design and Prototype-Brian Mackenzie Velocette engine work and machining

21/06/2026

Cruising through the glorious Scottish Borders on a perfect mid-Summers Day, on the Squish Head Vybrid,to join up with Velo friends at the Jimmie Guthrie meet st Dunhelm

I always put a retaining screw in sleeved barrels, having had two slide down (both done by a Velo main dealer).This was ...
18/06/2026

I always put a retaining screw in sleeved barrels, having had two slide down (both done by a Velo main dealer).
This was the first MAC I have sleeved and it is difficult. The normal placement of the bottom fl**ge is not available as the rings pass down further. I discovered, from the usual guru, that the rings stop ½” from the top in a MAC. It was a bit tricky but I managed to locate a 5mm screw ¼” down from the top, bloody tight and with a dab of green Loctite for good measure.
This one is headed for Tokyo tomorrow, so I can sleep soundly in my bed.

A bit of rotary table work. Worth its weight when needed.
17/06/2026

A bit of rotary table work. Worth its weight when needed.

Dry run at milling out a valve seat on a donor Valiant head, before doing it in anger on a customer Thruxton. I understo...
15/06/2026

Dry run at milling out a valve seat on a donor Valiant head, before doing it in anger on a customer Thruxton.
I understood the included angle was 90 deg on a Valiant. That may be true (I haven’t looked at the other side) but it certainly was not at 45 deg to the head face. Once that was adjusted it wasn’t too difficult except you can’t look at the cutter and reach the feed at the same time 😮, so a certain amount of faith is required. It came out ok in the end with a tap from a small cold chisel. I think it will be easier on the Thruxton with a lot more room to work.

Well pleased with the new (Chinese) 5 stone hone. Managed to get it exactly to size and parallel quite easily. I’ve fitt...
15/06/2026

Well pleased with the new (Chinese) 5 stone hone. Managed to get it exactly to size and parallel quite easily. I’ve fitted the piston assembly so that nothing gets lost if the packaging gets damaged on it!s way back to Tokyo.

Yet more fixtures, plus using the boring retainers to get set up for honing. After a false start using a mains drill I m...
13/06/2026

Yet more fixtures, plus using the boring retainers to get set up for honing. After a false start using a mains drill I modified the shaft to fit a Makita and all is well. You need three hands to keep squirting oil whist holding the drill but standing on the frame keeps it steady. It worked well even handling the cylinder cutouts without problem.

Couldn’t stand the mess any longer. Whilst the piston was cooking I made a tool board for the hot work area.
06/06/2026

Couldn’t stand the mess any longer. Whilst the piston was cooking I made a tool board for the hot work area.

New honing head commissioned after bonding on the stones and a shop made UJ drive shaft.
05/06/2026

New honing head commissioned after bonding on the stones and a shop made UJ drive shaft.

First job for our new heat treatment facility. “Cooking” a new piston the relieve stress, before final hone on the bore....
05/06/2026

First job for our new heat treatment facility. “Cooking” a new piston the relieve stress, before final hone on the bore. Also to be used for shrink fitting and tempering

01/06/2026

With the sleeve pressed and bonded in I parted off the excess and turned the ring entry on the bottom. I was pleased it went back in the fixture true (4 more Rizlas used).
Next I sharpened up the HSS tool, although it hardly needed it , and started rough boring out to near final size.
So far so good.

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Berwick
TD151UN

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