ClassicMotorcycleMechanicsJune2020

The first jobIhad to do was to strip
downtwoZ1crankshaftsandIwas
expecting some trouble!Irememberedthe
forcerequired to stripaZ1crankshaft
whenIwas making myKawasaki Z1600
V8 over20years ago, it stretched the
limits of myhydraulicpress andIwasn’t
looking forward to it. The first thingIhad
to do wasmakeacouple of support bars
from high tensile steel that fit between the
webs, making themasthick as possibleto
take theload required topress the
crank-pinsandjournals from thewebs.I
had alength of 30mm squareEN16 steel
bar thatwas ideal, soIcut of ftwo bits
aboutafoot long, but they would need
reducing to 23mm thickint he centre
using mymilling machine,sot hatthey
would fit in thegap between thewebs.
With th esupport bars machined I
offered up the crankshaftfrom unde rthe
pressuntilthe first webwas proudoft he
supportbars andIcould slidethem into
place ready to press out the first crank-pin.
To do thisIneededasuita ble pushbar
that was slightly smaller in diameter than
the 29mm Z1 crank-pin.Ihave abox of
old crankpinsthatIkeep for this purpose.
The push barwas thenplaced on to the
end of thecrank-pin andthenIpumped
up thehydraulic press untilthe ram
touched thepushbar an dresistancewas
felt.AtthispointIhad agood check to
make sure thecrankshaftwassitting
square, then started to pumpupthe
pressureint he hydraulic system. two tons,
five tons, eight tons,then at ninetons,

Pressing the second web from the
main journal.

Crankshaft parts ready for cleaning and assembly.

Setting web at 120 degrees on lathe. Webpress ed on to main journal.

with ahuge ‘Bang’, the first big-end

journal suddenlymoved acouple of mm

below theoutersurface oftheweb.

Great,Ithought,fromnow onthis one

will be easier.Istarted to build up

pressureagain,and sure enough at around

seven tons it movedagain, andafte rafew

more pumps of the lever the first webwas

free along with the first connecting rod.

The process was repeated on the outer

four websoft he crankshaft. Theinnerfour

webs on the firstcrankshaft could remain

assembledwith the two inner connecting

rods becauseIwoulduse this for the inner

portion of my newcrankshaft.With the

first crankshaftstrippedIhad to

completely stripasecond crankshaft so

thatIcould pick therequired webs and

two additional connecting rodsrequired for

the new six-cylinder crankshaft.

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