I find that this part of any bike project always seems to
take an inordinate amount of time. The main “chunks” of the bike are up together
– frame, forks, wheels, mudguards, engine, gearbox etc. but the number of “small”
detailed things that needs doing makes a seemingly endless list but it’s just a
matter of working through that list to complete the dry build.
The first task was to fit the exhaust pipe; this bike
competed in the TT with an open pipe exhaust and I have replicated that. Whilst
Mr Plod the policeman might not be too happy with the noise I don’t plan on
riding up the High Street of our local town too often. I had bought 2 exhaust
pipes from Armours – I have
been using their exhausts for many years and asked for a non-standard full-length
pipe (the standard, shorter offering, is truncated around the gearbox so that a
silencer can be fitted). I have always found that they make an excellent job of
getting the correct radii on the various bends in one continuous length of pipe
whereas I have to cut-and-shut a series of bends to achieve the same (see eg here).
However, the KTT pipe requires an upwards bend to avoid scraping
the ground. I ordered pipes in plain steel, ie no plating, as I knew I would
have to make some adjustments.
A lot of heat is needed to bend these manually and so I
fitted the exhaust to another of the dry builds, took out the gearbox (to avoid
any heat damage) and put on a spare cylinder and cylinder head to the scrap crankcases
already fitted and with some fire bricks beneath, I was able to “adjust” the
pipe into position with a lot of heat from the oxy-acetylene.
Fitted to KTT 305, it’s now positioned in the right place
and won’t scrape along the ground or interfere with the stand.
The rear support bracket has since been added.
I had changed the carburettor because there was some damage
to the top of the aluminium body and because I prefer to have the float bowl on
the left. This caused a problem that the advance/retard cable could not be
fitted into the square ML magneto. An angle piece was therefore made
to redirect the cable entry (now chemically blacked)
to avoid interfering with the bottom of the float chamber.
There are always quite a few oil pipes and connections to be
made and fitted but one, in particular, differentiates the KTT from many other contemporary
bikes and this is the size of the feed pipe which is ½” OD. Why did Velocette
fit such a large size? Because they were smart! The oil that flows into the
engine only has gravity to help it and, because the height of the oil tank is
not much above the entry point of oil into the engine, the head (to drive the
flow) is low. However, providing a pipe with a nominal 3/8” inside diameter does
2 things: firstly, the flow resistance is reduced compared with a smaller
diameter pipe and, secondly, it provides more of a “reservoir”, ie a volume
immediately adjacent to the entry point into the engine.
I did not have any of these larger pipes or the union for
either this bike or KTT 55 which requires the same. I measured the thread on
the large oil tap to be 11/16” and 20 TPI but did not have a tap (a threading
tap, that is) or brass hexagon bar of the appropriate size (7/8” AF) and so
these were ordered
together with some ½” OD copper pipe and 2 sets of unions were
made. Pipes were bent to fit,
silver soldered together
and connected to the K-119/2 union on
the engine with flexible pipe. These are listed as KA-72/2A in the Velo parts list.
The petrol tank had, up to now, been held in place by 5/16”
BSW bolts as a temporary measure but it was now time to make proper shouldered
bolts with their heads drilled for locking wire.
A new valve lifter spring that I had purchased turned out to
be ineffective in the respect that the “ends” were too close together resulting
in the spring not acting as a spring when fitted. One of the ends was carefully
heated using the smallest – a #1 nozzle in the oxy-acetylene and with the smallest
flame possible it was repositioned, taking great care to shield the rest of the
spring from the heat.
It now works perfectly.
The oil tank needed some work, specifically because it showed
quite a bit of corrosion on the inside. The black top coat of paint on the tank
was stripped using Nitromors but this did not remove the primer. The tank was submerged
in Rust Remover (9 litres!) in a polythene container
and this removed all the internal rust and, fortuitously, also
stripped the remaining paint.
I have used a sealant, POR15
, to seal pin-holes. To apply this, the inside of the tank needs to be completely
closed off (to be able to swill it round and wet all surfaces) and, to this
end, I had to make a threaded blanking piece (15/16” x 20 TPI) from a piece of
scrap aluminium to block the large oil tap hole and prevent the sealant filling
the threads.
One could also use a rubber bung or a piece of wood to screw
in ….but I didn’t have anything of the right size around the workshop. The filler
cap hole can be easily blanked off with cardboard and masking tape.
The outside of the tank, now bare metal, was given one coat
of etch primer to avoid it going rusty. I have found in the past that using any
rust-removing product makes the surface very reactive and unless treated immediately
a brown coating of new rust starts to form as soon as the surface has been
washed and dried.
Up to now, I have only had one new final drive chain and I
have been using this to check alignment of the rear wheel and gearbox
sprockets. I recently ordered the remaining chains for all 3 bikes
as these are needed to be able to set up the chainguards.
The 2-part chainguard for the final drive is a new item from
Grove Classics – FK28 and FK28/3 and fits pretty well.
It required a small lug to be made and attached to the
mudguard stay with the TIG welder and the front section needed a bit of tin
bashing to avoid the FK-167/2 footrest support stay (this was only fitted on
KTTs and the guard would fit directly in the absence of the support stay). The
front support bracket also needed extending.
The primary chain guard, however, was a lot more work. I had
only a generic guard with curved sections and, although it was well made, needed
quite a bit of fitting plus bracketry.
The bracket in the centre is silver soldered and the one at
the front is TIG welded to the guard. I use oxy-acetylene for silver soldering
and noticed not only a strong, unpleasant smell of acetylene but also an
audible “hiss” when I started this job. Not good. I ended up replacing the
hoses, the flame trap and, because the controls had become very worn over the
years, the torch. Better than getting blown up before finishing the dry build.
Having fitted the primary chain guard, I could now make the
pipework from the oil tank breather/overflow to lubricate the primary chain.
The engine plates have a ½” diameter hole that is used for footrests on non-KTTs
and this is conveniently placed to fit a retainer for the oil pipe. This was made
from a piece of hexagon bar
which was then blacked and a copper oil pipe bent to fit.
Next on the list are cables. There are 6 of these to make –
front brake, clutch, valve lifter, throttle, air and magneto. For many years I
have been attaching the nipples on cables that require more tension to be
applied in service – front brake, clutch and valve lifter using silver solder
(and also on the choke cable on the SU carburettor on the MG - see here) and soft (lead) solder for
the others.
The outer cable (or 2 sections of outer cable if a mid-way
adjuster is fitted) are first put in position on the bike and cut to length, the ends
cleaned up carefully (to avoid melting the plastic outer covering) on the
grinding wheel and all the constituent parts – nipples, ferrules, adjusters and rubber protectors assembled
in their relative positions
before threading the inner wire through, cutting to length and
fixing the nipples in place.
Some cables, for example, the valve-lifter need additional
components to be made, in this case to hold the nipple
and which is also the adjuster. I made 3 as the other bikes
will also need these.
All the oil and petrol pipes have been made with braided fabric-covered
pipe and secured using clips (these are listed as KA-100/4 and KA-100/2 in the Velo parts list) rather than ferrules.
The dry build is not yet finished – there are 3 more cables
to make, the tool box and petrol cap to be fitted and I have commissioned a
short bum pad as the ones that I have are too long and would look out of place
if fitted over the top of the mudguard stay. I’m sure there will be a few other
things but it’s getting close to completion. More next time….
