Often it’sbest to cut out
the damaged area, or at
least dress it up. Before
workstarts, measure
the length for removal
then proceed cutting or
dressing back to sound
metal.
Fabricateaninsert to suit from identical
diameter solidrod, in this case in mildsteel.
Create spigots ateither end forinserting into
the soundrodofthe carrier,mudguard stay etc..
To aid brazeflow,the spigots are shaped to a
light slackfitinternally to their mating tubes
and Itend tofile two mildflats to each spigot
at 180 degrees to each other,and to the tubes
under repair mildfiled recesses are created as
illustrated. However,manydon’tdot his and
finish with equally good results.
On brazing,aneven heat ensures the
brazing/brass rod will meltwell and quickly
toflow through the jointby capillaryaction. In
period, makersoften used hearths for this
purpose andwe could makeour own but gas
generated heatevenly applied workswell for
If required, createajig to secure the work
in the required form. In this casealength of
6mm builders’ stud workswell, but with mole
grips, clamps and lengths of black steel strip,
jigs have been improvised. Before workstarts,
Icheck length, truth andfit–although brazed
joints can be easily sweated aparttoi mprove
the job, it isadispiriting task.
small to medium sized jobs. Some prefer silver
solder,which alsoflows well in asimilar–but
not identical–heat range to braze/brass but
when dressed down to ultra-thin thickness (for
example, where it isflowed onto the rod and
perhapsfills ashallow dimple) it tends to peel
in my hands, which braze doesn’t.
Brazing is another procedure involving lots
of heat, which for safety reasons won’tbe
detailed here.We braze using the oxyacetylene
kit but equal results are achievable using other,
widelyavailable gas sources foramodest
outlay. After brazing,the workisc leaned
traditionally withfiles and then lengths of
emerycloth. The eagle-eyed will notice despite
careful jigging,the workisa bout 1mm out
of true. My excuse is itwaslate in the day
and Ihad an appointment with the products
of MessrsGreene and King.But the out of
trueness isn’taproblem, as the brazed area
to one side of the repair can be reheated for
the worktobetrued, brazefilled if required
(often not) and dressed up.
The above is taken from procedures which
workfor us. Manyother approaches will
achieve similar oreven better results and
our methods are based onover 50 yearsof
amateur metal mangling workonmypart, but
there’sno‘appropriate’ technical training,as
none exists for much of the workweneed
to undertakewhen restoring motorcycles. In
manyinstances, it isacase of making it up as
you go along!
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TODAY PAGE 22
Brassfloatchamber repair:
Rummagethrough boxesofcarburettor
parts and invariably we’llfindfloatbowls
with damagetothe union fastener boss/
thread. Whilereplacementsboth new
and second-hand areavailable for Amal,
Bing, Dell’Ortoand otherwell known
carbur ettors, earlier instruments are
precious and the following canworkwith
brassfloatchambers.Sometimes damaged
threadscanberestored with adie butifthe
boss is crushed, the job isharder.Here’san
approachwhich worksonsomeoccasions
and wasused for the AMACcarburettor
floatbowlfor my 550c cOEC Blackburne
whenfirst rebuilt in 1975-79 and although
still lookingalittle gnarled, thefloatbowl
hasservedthe machine since itwasfirst
firedupinmyhands inlate 1978.
96 THE CLASSICMOTORCYCLE|SEPTEMBER 2019
Technical feature|Restoration tricks
