classic motorcycle forum

Brilliant 33d6!! Just the information I needed.  Cheers!! Ian

Hi guys, thanks for you input. I reread the comments and omitted that it is a type ‘C’ gearbox and I have advertising material which says the McKenzie had either a 2 speed gearbox or a 3 speed gearbox, which cost an extra 6 shillings!! The gearbox has a ball bearing on the main shaft, but looks like a later replacement, as it is stamped with made in Sweden, which I don’t think the Brummies who made it used?? So  although it will do the job doesn’t look like an original part. The rest of the box gears etc is thou. I will rebuild this week end then bolt onto the bikes brazed on frame extension!!
Ian

Hi Thanks for the replies about my gearbox. The case is marked with use MobileOil “bb”. When I took it apart to restore the lubrication looked like a grease, but I suspect it had been taken apart before, I was given the honour. This is why I think the kickstarter spring was loose in the case!!

I assume I need to find a modern oil etc which has the same properties of the original or something which does the same job but in a more efficient modern matter?? To give you an idea of it’s age it is circa 1923, so obviously an antique and very little chance of a workshop manual/spare parts!!

Thank again for the info Leon, and it’s a Webb carburettor. I have the manufacturers “inventory” of most of the parts used on the bike  ie saddle manufacturer = brooks, choke control = Bowden. Just haven’t seen one on eBay yet?? I know I could get anything to work, just trying to be as original as possible..

Cheers Ian

Some good thoughts out there, 3D Printers are great but in metal does seem to be more expensive. I have seen some  “metal pipe joins” which seem to have the profile I am after, so I might be able to repurpose one of these to do the job. If not I can easily make a mould, but never tried metal casting before.Looks like it may be possible from home, depends on how much I want to burn myself lol!!

I have also tested and tried an aluminium block and can sort of make the bracket I need, but it’ll take an awful amount of cutting, grinding etc to get it into a shape which looks original.. perhaps as mentioned my local aero drone, where they repair aluminium engine blocks might have the skills/kit I need??

Hi Leon, the standard model as per your photo came without a gearbox, but for an additional £7 6s they would braze a mounting to the front of the frame, re-enamel it and give you a new gearbox, which sat in front of the frame and just behind the front wheel!! A metal chain connected the engine to the gearbox, which then powered the rear wheel via a belt. Why it all wasn’t a chain, I don’t know, I suspect might have been for better traction, but just a guess on my part!! Anyway my bike has the bracket on the frame so has been converted. I know i could have sawn it off, and gone back to standard, but as I have found the right gearbox, why not go the extra mile!! I just have to work out where I can get the right drive pulley and Cog which fit on the gearbox drive shaft and all should be good one!! Ian

Thanks for the info, I have seen a bolt type arrangement with a hole in the shank, which the spoke passes through, but at £20 for 4 seems an expensive way to do things especially as
You have to take the wheel apart to access the spokes.
Your idea seems a better solution, I guess I just need to find some small
Plates now!!