cmm
Allen Mill
Award-winning motorcycle
boresin th ecylinder heads andseating
area with brake cleaner, then tapped in
the newvalve guidesusing the special
drift andasmallhammer.The va lve seats
looked to be in excellentcondition and
after thevalveswere fitted andground in
withgrinding pasteaperfect seal was
achieved.The newvalve guideswere
masked with tape andthe heads sprayed
withsatin heat-proofpaintand left to dry
in the sun with the barrels.
The next morningItried the barrels on
to the engine first with no rings to check
everything rotated nicely,thenthe piston
rings, base gasket and head gasket were
added ready to put on the heads. The
valves were fitted first, then the press
steel cups and springs were followed by
the retainers and collets. The heads
were then fitted to the engine and bolted
down ready for the lower rocker casting,
rockers and pushrods to be fitted,
followed by the top rocker cover.Ihad
carried outasmall modification to drain
oil from the steel cups back to the
pushrod tubes using copper brake pipe
and ashort rubber joining pipe. The
Velocette engine was not fitted with
valve stem seals so oil can seep past the
valves into the inlet or exhaust ports
overnight, causingaplume of white
smoke on start-up.With the headsassembled and
bolted downIcould
set the tappet
clearance for each
valve in turn, then fit
the individual tappet
covers, and to
complete the top
end Ithenfitted the
inlet manifold.
The next job was to
fit the ignition drive
gear and points shaft
into the timing side
crankcase and fit the
new timing cover with
an integral bearing
and oil seal. This
supports the points cam that protrudes
through intoamachined recess that will
contain two sets of ignition points.With
the timing cover secured in place with
12 screws, the points plate could be fitted
and the timing set to 38 degrees before
top dead centre fully advanced for each
cylinder usingadegree disc mounted on
the crankshaft. Then the point’scover was
fitted and the engine was all together and
finished.Iscrewed inapair of spark plugs
and turned the engine over several times,
and was pleased to feel healthy
compression. cmmFront head and barrelfitted.Rockerboxes and inlet
Completed engine ready tofitbackontobike. manifoldfitted.70 / classicmotorcyclemechanics