RealClassic – August 2019

88 I AUGUST 2019 More old bikes online: Real-Classic.co.uk

Observehowthe balanceweight has halfawheel
missing

Cush drivedamage is plain. However, observethe

number of real properbearings

Working on these engines from thebottom up is

easy,apparently

Splitting thecases revealed‘enough debristo
growspuds...’

Exposedgearsandshafts, viewedfrombelow The lefthandthreadedring.Newring on left, the

butcheredoneon right,with the propertool nearby

Thecrankshaft hastwomassivecentre rollerbearings–observethelocating holes in each of thebearings.The second pic showsthepegs whichmust locate
in those holes

Thereareafew caveatsand tricksto
reassembling this engine from the bottom.
First,thetwocentremain bearings have
locating holes thatmatchcorresponding pins
in the lowercase.Theholesinthe bearings
must be in theexactpositiontomatchup
with the pins as the lowercase is loweredinto
position.Theway todo this istouseaset of
caliperstoaccurately measurethe positioning
of theholes.Thisdone, the lowercase half is
loweredonadummyrun: it can take several
goestoget it all in harmony.
Nextproblem is thatthe threeselectorforks
arelocatedinthe lowercase half (the big lump
youjust didacouple of dummyruns on).The

selectorforks havetomatchupwith the slots

in therelativegears;twoonthe mainshaft,

one on the layshaft.Thisisdead easy when

building from bottom up,but callsforsome

trickeryand thefingersofamidwifewhen

building upside down.

First,position the gears inaconcentric

patternbymeasuring the clearanceateach

end.Nowdaub somegrease on the selectors

wheretheyslide on the selectorspindle.Next,

another dummyruntomake surethe selectors

get matchedintotheirrespectivegear slots.The

engine must be absolutelyvertical because the

selectorforks aresimply dangling down from

the lowercase half as it is loweredintoplace.

Bysquinting intothe narrowing gap it is

just possibletoguide the selectorforks into

place. Tapthe casefully home and then check

thatyou haveall six gears.Ifnot: startagain.

If all iswell,verycarefully liftthe lowercase

offagain,keeping it dead horizontal so the

selectors do not move.Placeitonacouple

of blocks with selectors free fromcontact

with the bench surface. IuseaHylomar Blue

asasealant. Smear it lightly on the upper

case surfacebut don’t bother with the lower

case surfaceasyou can’t getatit without

upsetting the selectorforks position.

Oncemoreintothe breach: lowerthe case

down and checkforthose six gears before