1:B-Series’
statuesque,durable
engineand gearbox.
Mon oblo ccarbisa
lateraddition ,and
chromedtappet
coverastylingtouch.
2:‘Baconslicer’
frontnumber
plates were
mandat oryuntil
the early1970s.1 2
framerail.BSA’s advancedmetallurgy benefitted the
valves in thecast iron head.Thetrapezoid pushrod
towergavetheseenginestheir distinctivelook, with
the plateati ts baseprovidin geasyaccess for tappet
adjustment. And rightfrom1945, the B31 adopted
sturdytelescopic forks–anotherValPagedesign.
With 350beingthe favouredcapacity forboth
commutersand weekend sportingClubmen, the 17bhp
B31,with its crinkle-hub q.d.rear wheel, large capacity
tank sippingjuiceat up to 80mpg,and a70-plusmph
topend (with moreavailable ifyoufitted performance
parts from itsGold Star siblings),the 350became
BSA’sbest-sellingfour-stroke,averaging8000ayear
throughout the 1950s.However ,after sales hadpeaked
in 1955, aswith AMC,Ariel etc,350ccsingles beganto
go outoffashion and theirsales stea dily declined.
TheBSA lost its magnetoignition for 1958, theyear
that sawthe announcementoft he lighterbutmore
fragile unit C15, anearly clue to the new direction.The
B31 ceased productionat theend of 1959.Oneminus
pointhad been it sweigh t, which peaked with the
plungerversionat 420l b, whichwas45lbheavier than
the equivalentAriel NH.But the BSAdid winonthe
all-importantprice –in1953ithad been thecheapest
350cc ohvsingle on themarket.
However, the model’s strongest pointhad been its
reputation forreliability and durability.John Gleed,
chief mechanicat famous Gold Star specialist Eddie
Dow’sCotswold dealership,told me: “Theold fa rming
lads wouldalwaysbuy aB31 to ride towork.TheB31
wasjustsoreliable,and kept ongoing with aminimum
of maintenance.Anold boywouldfinally come in and
say: ‘Heain’t startingtoo good.’ You’dtakethe head off
and there’dbean1/8in gapinthere, so it wasamiracle it
starte datall!They’d come inwith the chain practically
draggingonthe ground and the primarychaincase
bonedry –‘he’s rattling abit...’”Ride on
Therewas notadropofoil on theseafront as we moved
offfrom takingphotos andIclimbed aboard. With 7.0:1
compression, the engine kickedoverand starte deasily
enough,and Ipulledaway, with the clutch andgearbox
both workingwell.
TheB31’sthumpingexhaust notewasatreat.Thehot
sunwas shiningand in the blueskyabove,the drone of
high-wingsingle engine propeller planes completed the
period picture. We climbed an initial hill in thirdand
hit top when itflattenedout beforethe summit.Overall,
the gearing felt quite high,whichwouldalsohave
contributed to lowwear.
An theroad, amix of up-and-down bends and long
straights, the B31handledreallywell foraplunger-sprung
machine,certa inly betterthanmyown previousold
and well-lovedM21.Russell’s work on the plungers had
beenworth it,and youcould putthe 350 intobends
with confidence.
Thesprungsaddlewascomfortable,and though
Russell hadwarnedmethat there-linedseven-inch
fron tbrake still needed work –he’dhad thehub
skimmed,butrebuildinghad distortedthe wheel and
it ne ededre-skimming–this wasbalanced by areally
effectiverear anchor,and together theycould copewith
the 50-plusmphride and the holidaytraffic.
However, therealflyinthe Castroleasewasthe
hesitation and falteringthe enginesoondeveloped in
three and top,almostcertainlydue to theinadequately
rebuilt magneto.Thehot weather –itwas thewarmest
dayofthe year so far–probabl ydidn’ thelp.
Afterafew milesIbegan to worry that the engine
mightdie,and with the 10-mileruncomplete,sure
enough it expired as Icoastedintothe carpark
rendezvous. Russellisg oingtosubstitute anothermag
to confirm thediagnosis.
Meanwhile thereweremorephotographic chores to
complete. With achangeofplug andapushstart, the
B31 undertook miles morephotographic pass es,before
Russell rode it home.
Youjustcan’t keep agood BSAdown.End