KAWASAKI Z1325

Our Ralph this month is as­sess­ing the Big Zed’s gen­eral health.

Classic Motorcycle Mechanics - - CONTENTS -

Ralph Fer­rand with part two: the heart of the Z.

Last month I started build­ing the bot­tom-end of a fire breath­ing mod­i­fied Big Zed. The orig­i­nal Z1 was no slouch, but this big block mo­tor should chuck out some se­ri­ous gee gees on the dyno when built. With an engine churn­ing out so much more power than the orig­i­nal de­signer fore­saw, it is es­sen­tial that ev­ery­thing is in per­fect fet­tle. The Big Z en­gines were mas­sively over en­gi­neered back in the day and lend them­selves to se­ri­ous tun­ing. I’ll start this month with en­sur­ing that the oil pump is tick­ety-boo. I tend to re­move the strainer gauze first and en­sure that it is 100% clean and is in no way re­strict­ing the oil flow. I cleaned it well with brake cleaner and lots of com­pressed air. I en­sured that there were none of those hard lumps of crap that seem to get burned into the gauze over the years, prob­a­bly from poor qual­ity oil and/or neg­li­gence. I tend to care­fully pick at the lumps with the sharp point of a scalpel. I al­ways wear safety glasses do­ing this! When held up to the light one should be able to see through all the holes in the mesh. The next job was to en­sure that nei­ther the pump body nor the pump gears were worn. They rarely do wear, but one must be 100% sure with this. The pump was se­curely gripped in my bench vice with the oblig­a­tory soft jaws in place to pro­tect this valu­able com­po­nent, and the cir­clip hold­ing the gear driven from the crank­shaft was re­moved and the gear was pulled off the shaft. The driv­ing/lo­cat­ing pin was then re­moved and stashed safely fol­lowed by the washer be­hind it. Then the screws hold­ing the cover in place were re­moved and the cover lifted off, re­veal­ing the gears. The gears were pulled from the body, tak­ing dili­gent note of what went where. Ev­ery­thing was thor­oughly cleaned with brake cleaner and I care­fully re­moved the old gas­ket from both mat­ing faces with a scalpel, tak­ing good care to re­move all the ma­te­rial, par­tic­u­larly around the lo­ca­tion dow­els. I very dili­gently vis­ually in­spected the pump gears and they looked fine.

I re­placed them in the pump body and mea­sured the clear­ance with the pump body with feeler gauges (see photo). Ac­cord­ing to Mr Kawasaki the stan­dard clear­ance is be­tween 0.011 and 0.083mm and so my mea­sured 0.06mm is fine. There is a stated ser­vice limit of 0.14mm. Be­fore re­plac­ing the cover one must en­sure that the all-im­por­tant lo­ca­tion dow­els are in place and that a new gas­ket is fit­ted. I ap­plied a drop of thread lock and seal to the screws be­fore I torqued them down to the set­ting spec­i­fied in the man­ual; you re­ally don’t want to be fit­ting Heli­coils in your oil pump! I then re­placed the washer and then the drive pin be­fore pop­ping the gear back on and se­cur­ing it with a new cir­clip. Be­cause this is go­ing to be such a beast of an engine, it was de­cided not to just re­place the starter clutch rollers and springs, but ac­tu­ally the whole clutch with gen­uine parts. The al­ter­na­tor ro­tor had ham­mer marks in it and didn’t seem espe­cially mag­netic so this was also re­placed with a pat­tern item from Elec­trex World. I re­built the starter clutch onto the back of the new ro­tor. As you will see from the di­a­gram, there is a rub­ber damper fit­ted be­hind the starter clutch gear. There are three dif­fer­ent sizes of this part with a dif­fer­ent depth of rub­ber lip. The clear­ance mea­sure­ment be­hind the starter gear must be de­ter­mined and then the cor­rect damper rub­ber can be ob­tained. The small­est lipped damper for a clear­ance of be­tween 5.06 and 6.05mm has a sin­gle star moulded into the rub­ber and has a part num­ber of 92075-192. The next size up for a clear­ance of 6.06-7.05mm has two stars and the part num­ber is 92075-193. If the clear­ance is be­tween 7.06 and 8.05mm the part num­ber is 92075-194 and it is iden­ti­fied with three stars. I have built many Z en­gines over the years, but this is the first where I have had to change this damper rub­ber. The one that came with the engine was in­cor­rect.

Re­mov­ing the old gas­ket – very care­fully!

The bike as it was back in the day.

Re­move ALL the gas­ket: par­tic­u­larly around the dow­els.

Check­ing the clear­ance in the pump gears with a feeler gauge.

Use a torque wrench to tighten the cover screws.

Tight­en­ing the bolts that hold the starter clutch to the al­ter­na­tor ro­tor.

Fit­ting a new gas­ket to the pump it­self.

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