The Knowledge - Velocette Owners Club

the pump circumference, I put one between the pressure and scavenge side and another at the other
end of the pressure side to seal potential leakage and sucking air into the pressure side. My KTT had
bean oil when I got it. I flushed it with conversion oil to avoid teardown (mine was Blendzall, didn't
know Redline made it). Problem was the stuff cleans so well it dislodged years of swarf which ended
up plugging the oil system. I ended up tearing it down anyway. Alan Goldwater (writes Alan's Wrench
for NOC) sold me on the Redline oil. He did a heap of testing with heat sensors, lab analysis, etc. and
found it to be the best, Mobil 1 also very good but Redline comes in straight 50w. Before you say it, I
know some of you performs his yearly oil change outside the McDonald's on day one of the rally using
oil from the French fry vat and seem to get away with it.
L # VOCNA 318 On the standard Velo anti sump system, the column of oil under the ball valve
must remain in place because if it were to 'leak down', it would have to be replaced by air. Since there
is no way to supply air, it cannot leak down. That column of oil must be in place before running the
engine, as the oil pump cannot pump air efficiently enough to open the ball valve against it's supporting
spring. Using a weaker spring is not required, as if the supply line is properly filled with oil, the pump
will open the valve due to efficient 'suction'. In reality, there is no such thing as 'suction', but simply
pressure differential (above and below the ball). Above the ball you have atmospheric pressure plus the
weight of the vertical column of oil described as the area of the cross section of the supply line
muliplied by the height of the oil measured from the surface in the tank to the supply orafice to the
pump gears (assuming no air bubbles). When the pump begins to move that column of oil, the entire
weight of the column is moved by the pump, aided by the atmospheric pressure. The ball absolutely
cannot remain on it's seat, as there is no way for any air to enter the vertical oil column and the oil
cannot be either compressed or expanded as it behaves as a 'fluid solid'
# VOCNA 380 The check valve is a great idea, but I'd put it down by the oil pump, not on the underside
of the oil tank. With the check valve up at the tank, the oil pump may be forced to suck 6 inches of pipe
air to pull the valve open. Mirek says his will do that, so that's good. But some say you must fill the
pipe with oil. Which is it? Putting the check valve down on the motor, right next to the pump,
decreases the amount of air that the pump may have to suck to open the valve. Also if the bike wet
sumps without any valve, and you then install a check valve at the oil tank, wouldn't the oil in the pipe
(between the check valve and the motor) just wet sump too? Or does surface tension keep the oil in
the pipe? It must, otherwise the pipe would be full of air after a few days.
# VOCNA 385 I hadn't thought about the need for air to get in to allow the oil to leak down.
# VOCNA 382 It is right that the pipe must be filled with oil - I always prime the pipe with oil before start
up. I did my test by sucking on the end of the pipe which, for reasons of personal taste, was devoid of
oil at the time. The oil that is in the pipe between the valve an the oil pump should not leak through to
the cases as there is no way air can get in to allow the oil to flow (this is, for some reason hard to
explain). It is the same principal as a pipette - fill a tube or pipe with a liquid an put you finger over the
top - the oil will not drain out unless you lift your finger off and let air in to displace the oil. As I
mentioned in an earlier note on this - it is really important not to have any air leaks in the oil supply line,
regardless of whether you have a check valve or not. If you have an oil leak the oil pump will be
sucking some air in as the engine runs (probably sucking more air at higher RPM as the pump will be
turning faster). The check valve may work as well at the engine end of the supply pipe, but would be
harder to fit given the way the pipe winds up into the tight space between the gearbox and the engine
cases. The VM check valve was originally fitted near vertical on the bottom of the oil tank and so was
designed by Britain's finest engineers to work this way - how could you doubt them? Seriously, I have
no idea if anything but a more or less vertical mounting affects the operation of the valve - would the
ball still seat OK if the valve is on its side?
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