Larby from the UK contacted the web-site in August 2008. As the new owner of
a 1929 347cc Model 1 or Model 2 side-valve machine he had a good deal of
work ahead of him to get it back on the road.
included the fabrication of the complete kickstart mechanism for a Sunbeam
'AT' wide-ratio gearbox. The required components were illustrated in an
excerpt from the 1928 Marston's parts catalogue which was e-mailed (below).
I had some sympathy, the segment itself has been in poor condition on every
engine I've pulled apart - worn-down and missing teeth.
Some research from
the Marston annual spare parts lists revealed that the parts were common to
the 1928, '29, '30 and '31 side-valve models (and OHV models with the
exception of Model 10).
Marston's lists in
the late 1920s and into the '30s have two reference numbers for parts,
seemingly a system introduced in 1927. In 1927 each part was given an 'order number'
with a letter 'A' prefix. This was used for the purpose of ordering the
part. Alphabet lettering was used for the following years,
hence the 'C' designations in the diagram above denote parts from 1929
(although with no model changes, 'C' was also used for 1930).
The second reference
number is a unique factory number for the particular part. This only changed
when the design of the part changed. Hence the segment shown above as
'C.527' for 1929/30 is shown as 'D.782' for 1931. In both cases the
factory-only parts reference number is '4517' - no change. In 1932 the segment has a
factory-only parts reference number of '4157A', indicating a change to the
Photos of the
With that pearl of
Marston knowledge, it seemed the parts on my own 1931 Lion would fit the
1929 Model 1 or 2. As a compromise between making full technical drawings
and sending parts off as patterns, I was able to provide photographs against
10mm squared paper which with a few critical dimensions would hopefully
assist fabrication of a set of parts. I advised as follows in an e-mail:-
"I have disassembled a
kickstart from a 1931 Lion and have taken photos. I have photographed them
against 10mm graph paper which may help you gauge some of the dimensions.
You sent me diagrams with 'C' serial numbers (1929-30) so I assume that's
the date of your bike. I have had a look at Sunbeam spare parts lists and
the 'D' serial numbers for 1931 have the same 'factory use only' reference
numbers for the parts you list. I hope the photos help.
"For info, the segment
has a 2.5 inch radius, with fixed teeth over 140 degrees (loose tooth
excluded). It takes the kickstart shaft which is 5/8 inch diameter and 8 -
1/4 inches long. The loose ratchet pinion is 2 - 5/16 inch diameter and has
20 teeth. Its width is 3/8 inch on the outer face. The central 'boss' on the
inside face (onto
which the spring fits) projects 7/32 inch. The
central hole is 7/8 inch."
Note: the sprung
tooth that slots into the segment is missing from the photos. Its purpose is
to 'key' the teeth of the segment into the loose ratchet pinion on the
clutch / drive shaft.
The resulting fabrication
On the basis of the photos and dimensions
from the machine, new parts were able to be fabricated. These were made for
Clive by Harold Beal - photos of his superb work in making sense of the
limited information he had got for the precision manufacture of these parts
speaks for itself.
The end result is shown in the photo
below with kickstart segment and crank lever in place. Visible behind the
clutch 'basket' is the sprung, loose ratchet pinion against which the
segment engages. An excellent job!
Good luck to Clive in finding an outer
half to the primary drive cover, piston, main bearings, fork springs and an
Clive contacted the web-site in July
2009 with an up-date on progress towards his target of participating in the
Sunbeam MCC's 'Garden of England Run'.
Read more ...