Subscribe and save:www.Real-Classic.co.uk/subs AUGUST 2019 I83
waitingforthose to arrive,Iremovedthe cam
boxtocheck valveclearance. Unbelievably,
no adjustment of the eightvalveswascalled
for. No wear to be seen on anything.
Likewise,the O-ring drivechain wasstill
serviceable.Inf actthe only thing the bike
requiredwasthe replacementoft he sand-
cast magnesiumrear wheel dueto some
cracks.Astandardproduction alloywheel
went straighton. This again underscores the
very sound,almost indestructible natureof
the 500twin’s design.
Theraceitself wasonpubli croads across
the Baja peninsula fromcoast to coast.We
wonthe 500class and,had it notbeen for
amid-distancecompulsoryfuel stop,we
would certainly have taken the open class as
well.Despitethisunnecessarystop, we were
second in the full-blown openracerclass at
an average speed of...101mph.That wasthe
last race thatPeteand Iparticipatedin.
Afte rthatdemonstration of superior
design, braceyourselfforthe unexpected
tale of woe aboutatroublesome Alpino
whichfollows.Itc ame fromacollectorwho
wasthinningthe herd. When it arrived, I
waspleasantly surprisedto see thatthe
condit ion ofthebikeseemedto be closeto
the‘tidy rider’spec as depictedonthe photos
sentbyvendor.Asisnormal, the battery
wasuseless.Withanewonefitted ,the 500
reluctantlyfiredup. Let’stry it down the
lane.Performancewas sadly lacking below
6000rpm, afterwhich it would suddenly
take offwith alacrity. This wasindic ativeof
summatradically wrong,and thatwas only
half of it.Ata nything above idle ,the engine
vibratedverybadly.Att he above-mentioned
6000 revs the vibration wasverysevere
indeed.Itw entonto the benchforsome
urgentinvestigation.
Isuspectedsome sortofmess-up with
the engine balancer,sooffcomes the drive
side clutchcoverfor alooksee.Nothing
untoward;the balancerwasfreeand running
on good bearings.Out with the plugstocheck itwastimed correctly.Whoops,here
we go,the balancerwastimed‘halfcorrectly’
with one pistonat TDC. However... thatwas
the wrong piston!
Theweightoft he balancer must beat its
6o’clock position with the leftpistonatTDC.
TheLaverda 500twin hasa180-degreecrank
layout,ie: one piston up,t’other down.This
results in perfect primarybalancebut at the
expense ofarockingcouple.Thiscouple is
the alternating side-to-side motion asfirst
one piston then the other triesto rock the
engine sideways.Tocountera ct this,there is
abalancer installed which is basicallyasmall
steelflywheel with half the wheel missing.
This contra ption is ofcourse wildly out
of balance, but by timing its out-of-balance
natu re correctlyto the rockingcouple of the
reciprocating (up and down) parts of the
engine,the result is blissful harmony.
Had Mr Bodger leftthe balancer out,the
enginewould run acceptablywell with some
mild vibration. But timed as he had done,the