Thursday 20 April 2023

Velocette KTTs 55 and 305: Project Kick-Off

Anyone working on Velocettes very soon realizes that part numbers are central to the language of repairing and restoring Velos. For the early cammy Velos there are 2 lists of spare parts with accurate depictions of all the various bits and which are essential to identifying all the parts and their variants. One list covers years 1925 to1931 and the second is for 1932 to1934.

The Velocette system is quite logical in that a /N is added to distinguish between either variants of a particular part (for example, K-27 /…. are all pistons for different applications) or as the design evolved (K-92 and K-92/2 are both camboxes) in the above illustration.

Whilst I plan to restore KTTs 55 and 305 I also have a KTP frame (essentially the same frame as the KTTs but, as luck would have it, with a forged rather than a cast bottom rear frame lug where the gearbox hangs ….actually a stronger frame) that I will use in due course for a cammy “bitsa”. And so, where the opportunity arises, I will attempt to gather 3 sets of any particular component rather than 2 in anticipation of this next project.

Firstly, KTT 305 was put up on the bike ramp:

As I mentioned in my last blog post, this bike was raced hard in Vintage Club events 40 years after it's TT debut. In fact, the engine clearly suffered a serious failure at some stage of it’s later racing career as the original drive-side crankcase has been severely damaged, repaired and then replaced. The original, which came with the bike, looks like this:

and with big cracks on the inside surface. Definitely beyond redemption!

Judging by it’s external appearance, the remanufactured drive-side crankcase that is on the bike has been extremly well made and the engine was running when I acquired it.

As far as I can tell, most of the bike is original although there are certainly a few bits that have been replaced: the oil tank (which should have the filler on the other side), the carburettor (it has a later AMAL TT carb) and obviously the addition of a bump seat plus some other details.

It was time to start rummaging through the many boxes of bits in my workshop, my garage and the workshop loft to make an audit of what I have and what I don’t have to determine which bits I need to find or make.

After a couple of weeks, I assembled the collection of the main bits relevant to these projects and brought them out into the daylight:

In the above picture, the frame is the later KTT frame that came with the KTT 55 project. I haven’t pulled out the KTP frame and another set of KTT strutted forks and there are another 3 early engines not shown here but this was sufficient to get started.

Petrol Tanks

As I mentioned in a previous blog I used to travel to India quite frequently in my working life and I took the opportunity to get some Mk 1 cammy petrol tanks made. This is a picture of my tank maker, Mr Sridhar, and myself having a hug in the back streets of Bangalore and in front are a couple of Velo tanks in the making.

I ended up with 3 beautifully crafted tanks in the correct gauge steel and the correct threads that I will now use on both KTTs and the KTP-framed bike.

Oil Tanks

Luckily I have the original KTT oil tank that came with the KTT 55 project and I picked up another one a few years ago on ebay.

Both KTTs will therefore have the correct tanks.


KTT 305 (on the bench) obviously has wheels and the front wheel has the correct size rim but both will need rebuilding. Rusty wheels came with KTT 55

and I have another front hub, brake plates and brake shoes


but I am missing a rear hub for the KTP-framed project (part number KS-7/4) and KS-2/3 (brake drum and sprocket – available from Grove Classics). The front brake plate that has disintegrated is from KTT 55 but I have new castings to be machined to replace this, noting that the boss for the brake fulcrum is slightly longer on KTT models.

Head Steady Clamps

I have one original and a number of castings in both cast iron and bronze that need machining.

However, as I was pondering why KTT 305 (on the bench) doesn’t have a head steady I noticed that 2 pairs of head steady clamps have been used as handlebar clamps!

and so it looks like there will be a few spares of these.

Handlebar Clamps

I have one set of original and correct handlebar clamps that came with KTT 55.

and so I think I will be using these to make patterns/castings for the other bikes at some time in the future .

Engine Plates

Although these are relatively straightforward to make, I acquired 3 sets of new manufactured and beautifully made plates a few years ago.

This will save a few hours of work!


These are readily available from Renovation Spares these days (contact Simon at but I already have 3 sets of mudguards in my workshop loft that are the correct size for 21” wheels.

Chainguards and Stands

I have a sufficient number of stands

but not enough chainguards.

Luckily, rear chainguards (FK-28 and FK-28/3) are available from Grove Classics ( but I will probably have to use other tinware for the primary drive as this is not readily available.


KTT 305 has a running engine but I have no idea yet of the condition of it inside. Superficially, it appears to be in good condition (albeit with it’s remanufactured drive-side crankcase). As I already mentioned, it has the incorrect carburettor but I have a number of the correct size AMAC TT carbs that have been refurbished by Martyn Bratby and these will be fitted to each of the KTTs.

Much work has already been done on the engine for KTT 55.  Some years ago, when Max Nightingale was still alive (RIP Max) and managed Alpha Bearings in Dudley he made an entire new crankshaft – flywheels, mainshafts and con-rod for this engine (although the superb craftmanship can’t be seen in the picture below)

The collection of bits for this engine came with a brand new bronze head rather than the cast iron head that would have been fitted originally. This would have been for use on a later Mk IV KTT and I can only guess the reason as to how it came to be associated with this earlier KTT.  I have already fitted this head with new valves/guides/springs etc and fitted a cambox.

The barrel has been sleeved and nikasil plated and 4 new pistons and rings suitable for running in a nikasil bore were commissioned.

The forged pistons are replicas of an original KTT piston that I have (albeit with a slightly reduced small-end diameter) and were made by JE pistons in California and the rings, which are suitable for a nikasil plated bore, were made by Total Seal. I have already used one of these pistons and ring pack in the AJcette engine with good success (see . The crankshaft was balanced to this piston.

I haven’t yet decided which engine to fit in the KTP-framed project. At the same time that Alpha Bearings made the new crankshaft for KTT 55, they also made a new crankshaft for one of my other engines.

Another candidate engine would be from a very early Model K

although this would be more suited to one of the early flat-tank projects.

Crankshaft Shock Absorbers

I had 4 sets of these made a few years ago.

These are pretty complicated parts to make with many machining operations. I have used one on the AJcette and the others will be used on these and other future projects.

Exhaust Rings

I needed to make a couple of the early exhaust rings (K-66) for the V-Twin project and made some castings in Ni-Al Bronze (AB2) (see and I will need 2 of these for the KTTs rather than the later type (K-66/2). I still have 4 unmachined castings that will be used here.

Internal Engine Components

I have plenty of bevel drive gears/shafts/oil pumps etc and aluminium timing-side casings ….this is just some of those that I pulled out:

I am not anticipating needing any additional bits here.


Last, but by no means least, 2 gearboxes (in addition to that already in KTT 305) and foot gear change (Part # GC50) are needed. KTT 55 came with it’s original gearbox and I acquired another at some time in the past although one of these is missing a mainshaft.

I also have a couple of new-manufactured gear cluster sets that may come in useful and there are sufficient external foot change mechanisms.

There are plenty more bits that haven’t been covered here but at least I now have a better idea of which of the major parts I have and what I don’t have.

Anyone that has read by previous blogs will know that I always aim to get a rolling chassis assembled as the first milestone – frame, forks, wheels and rear stand. There are 2 reasons for this: firstly, everything else “hangs off” this and, secondly, it’s easier to move the project bike around the workshop – very important when you have limited space. And so, work will now begin in grit blasting those parts that have surface rust and sorting out the forks and wheels for KTT 55.

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