KAWASAKI Z1325

Ralph again, on with part one of this Zed pow­er­house.

Classic Motorcycle Mechanics - - CONTENTS - WORDS AND PHO­TOS: RALPH FER­RAND

When some­one asks me if I can build a Z1000A2 mo­tor the an­swer is: “No sweat, I can al­most build ’em blind­fold these days!” A Biker’s Tool­box cus­tomer rang me and asked me some tech­ni­cal ques­tions about work­ing on Kawasaki’s finest, the Z1000, and I was happy to prof­fer some ad­vice. I had a look at a very in­ter­est­ing en­gine he has for a Rick­man, which had a huge amount of high-qual­ity pe­riod race tun­ing work done to it. A while later a now fa­mil­iar South Wales voice rings up and asks if I could build up a Z1000 en­gine for him. I had al­ready put a Z1000ST en­gine to­gether for his brother in a short space of time, so I as­sumed this would be a sim­i­larly quick job: how wrong could I have been? It was ex­plained that more than 20 years ago a rather over-con­fi­dent young Welsh­man had rung the neck of his hard-worked, tuned Z1000 once too of­ten and to­tally blown the en­gine to smithereens. He had stripped it and bought lots of very ex­pen­sive, hot tun­ing parts for the bike and then, well, noth­ing re­ally. He ended up buy­ing an­other bike to abuse and the parts re­mained in a se­ries of garages for two decades and sadly quite a few bits suf­fered from be­ing in none-too dry lock-ups on oc­ca­sion and some bits got mis­laid. This was clearly no nor­mal en­gine build and would test my en­gine skills to their lim­its. As the crankcases were pretty scuzzy I rec­om­mended get­ting them sent up to Steve Smethurst to get them cleaned to within an inch of their lives. They have to be com­pletely stripped of ev­ery­thing in­clud­ing dow­els and all studs. He then plugs up all the oil­ways etc. be­fore vapour blast­ing the cas­ings and then treat­ing them with a mass vi­bra­tion tech­nique that leaves a fin­ish bet­ter than new, which stays nice for far longer than with other tech­niques. The down­side, from my per­spec­tive, is that when the cas­ings come back, I have to clear out all the threaded holes by firstly blow­ing them out with

com­pressed air, then run­ning a tap through them and fi­nally blow­ing them out for a sec­ond time. This is quite a ball ache as there are lots and lots of threaded holes on a set of Z crankcases. Once cleared out, I mark the hole with a Sharpie to en­sure I don’t miss any. Part of the vi­bro-process uses var­i­ous sized ball bear­ings which can jam up a thread. You have to be very care­ful as a small ball can jam the tap mak­ing it easy to snap it off, lead­ing to more work and costs. I had no prob­lems with this build, but I did have an un­seen ball un­ex­pect­edly jam a tap when clean­ing out the carb rub­ber mount holes on a Z1A head once. I had to take the head to an en­gi­neer­ing com­pany with spark ero­sion equip­ment be­cause this is the only way to re­move a bro­ken tap. The cost of that mis­take has stayed in my mind for years, mak­ing me ex­tra vig­i­lant these days. I don’t think I have ever re­built an en­gine without hav­ing to drill out at least one bro­ken off screw/bolt/stud, more of­ten than not one or more un­der the fi­nal drive cover of a Z en­gine. So many DIY me­chan­ics just ig­nore such things, seem­ingly in the be­lief that the man­u­fac­turer put in ex­tra screws/bolts just for a laugh. They didn’t and trust me – no pro­duc­tion mo­tor­cy­cle has any fas­ten­ers fit­ted to it that aren’t es­sen­tial, even if the bike will lope along for a while with some miss­ing bits. From my per­spec­tive, it tends to be bet­ter if the bodger hasn’t tried to put right their cock up, as re­mov­ing sheared fas­ten­ers re­quires a fair de­gree of skill, so DIY at­tempts gen­er­ally cause more dam­age. Drilling steel screws out of alu­minium is quite dif­fi­cult, be­cause the drill al­ways wants to wan­der off into the soft alu­minium. Even when you have a small part you can clamp in the ma­chine vice of an ac­cu­rate milling ma­chine, the drill will still try and take the path of least re­sis­tance. The an­swer is tool­maker’s but­tons. These are hard­ened ‘top hat’ shaped bushes. As I didn’t have any proper tool­maker’s but­tons of the cor­rect size and given I wanted to get on with the job straight away, I made some tem­po­rary bushes on the lathe out of mild steel. They’re not ideal, but they got me out of a hole. I man­aged to drill a 3.2mm hole fairly con­cen­tri­cally in the re­mains of the screw us­ing this method. Rather than try and drill the whole lot out, I thought it was worth a try with a pro­fes­sional ex­trac­tor. I warmed up the area with the heat gun to ex­pand the alu­minium and squirted some ACF-50 at the of­fend­ing ar­ti­cle, which is a sur­pris­ingly good pen­e­trat­ing fluid, though it isn’t de­signed for that task specif­i­cally. NEVER use a cheap Easy­out type tool, be­cause you’ll likely end up snap­ping it off and pay­ing money to an en­gi­neer with a spark ero­sion ma­chine to re­move the re­mains. I speak from bit­ter ex­pe­ri­ence. Never put too much force on an ex­trac­tor and if in doubt give it to an en­gi­neer to fin­ish. I was lucky with this one and it came out without too much of a fight. In the pho­tos you’ll see I had marked the hole ‘HC’ for Heli­coil. If you can’t get the re­mains out like this, the chances are with a small M6 bolt that the threads aren’t go­ing to sur­vive, even if you are suc­cess­ful in drilling the in­ner part of the bolt out per­fectly con­cen­tri­cally. Pick­ing the re­mains of the bolt threads out of the threaded hole is pretty tricky and I would usu­ally fit a Heli­coil as a matter of course. The thread will have had too much torque ap­plied to it for the bolt to have snapped off any­way. It turned out that the en­gine wasn’t a reg­u­lar over-size en­gine, oh no, this has big block with

a swept ca­pac­ity of 1327cc! The en­gine cas­ings had to have the holes for the bar­rel sleeves ma­chined out to take the mas­sive big block sleeves. I was also given a set of APE 435 high-lift cams to use. Twenty odd years ago the head had big over-size valves fit­ted and some port­ing work to boot. With all the huge amount of ex­tra power likely to be gen­er­ated, a stan­dard pressed to­gether crank shaft would not be safe and could po­ten­tially twist, so we sent it off to be welded-up and dy­nam­i­cally bal­anced. If you look in the pho­to­graphs, you will see a se­ries of holes drilled in the crank-shaft webs, these are to re­move weight in cer­tain places to get the crank-shaft bal­anced. A bit like a wheel bal­ance, but in­stead of adding weights you are re­mov­ing weight at strate­gic points. The first stage of the build is to as­sem­ble the uber-heavy duty gear­box com­po­nents and crank-shaft into the top crank­case. I can still re­mem­ber my shock when I first opened up a big Z gear­box – they’re mas­sive and so can deal with huge amounts of power. I use an en­gine build stand I made my­self, which is great as I can turn the en­gine eas­ily through 360°. Be­cause this mo­tor is likely to put out a whole heap more power than stan­dard, I fit­ted high ten­sile studs to re­place the stan­dard bolts that se­cure the crankcases around the crank-shaft bear­ings. A new top-qual­ity heavy-duty cam-chain was fit­ted, as it has a hard job drag­ging those mas­sive, steep cam lobes around. I re­fit­ted the two lo­ca­tion dow­els front and back, the kick-starter gear and the odd tri­an­gu­lar sec­tion rub­ber O-ring just behind the crank-shaft that is the main oil feed up to the top end. The steel ratchet gear arm stop­per for the kick-start mech­a­nism must have the tabs on the locking plate tapped against the hex flats of the two 8mm bolts se­cur­ing it, to en­sure they do not undo from vi­bra­tion. The outer rings of the main bear­ings have shal­low blind holes drilled in them which lo­cate in small solid dow­els in the top case. I have known peo­ple not line these up prop­erly and I can as­sure you it makes a big mess that’s very hard to put right. These dow­els are hard­ened and so if they’re forced in blind, there will be an­other trip to see the spark ero­sion man! One im­por­tant rea­son for the dow­els is that there is an oil­way drilled into each outer race which must be lined up with the oil­ways that feed them in the crank case. I re­fit­ted the gear­box se­lec­tor drum with the third gear se­lec­tor fork, re­mem­ber­ing to se­cure the guide bolts with a new tab washer. Don’t want that com­ing loose! Al­ways use a new lock washer when in­stalling the shift drum guide bolt. When as­sem­bling an en­gine unit ev­ery­thing should be lu­bri­cated with a min­eral en­gine oil. There is a heavy bear­ing cap that is fit­ted over the in­ner-most roller bear­ings which is the last thing to be fit­ted be­fore join­ing the cases and should be torqued down in the pat­tern spec­i­fied in the work­shop man­ual. This bear­ing cap has an ar­row point­ing for­ward and must be fit­ted the cor­rect way around i.e. the way it was line-bored dur­ing man­u­fac­ture. The mat­ing faces on both cases should be scrupu­lously de­greased us­ing brake cleaner or a sim­i­lar volatile, rapid dry­ing de­greaser. As al­ways, I painted the mat­ing faces with my old friend Wellseal, us­ing a cheap ny­lon artists’ paint brush sourced from Lidl. I let the Wellseal flash off for 10 min­utes and then care­fully fit­ted the bot­tom case in place. The nuts were then care­fully fit­ted to the 8mm studs that se­cure the crank bear­ings. The two outer rear ones need to have a light smear of sil­i­cone un­der the heads of the flange nuts. There are num­bers cast into the bot­tom case near these studs de­cree­ing the or­der these must be tight­ened in. I usu­ally tighten them all down to 10lb-ft in the cor­rect or­der and then to the rec­om­mended max­i­mum of 19.5lb-ft. I then fit­ted all the 6mm bolts in place and used my ¼in drive torque wrench to tighten them all down to the spec­i­fied torque of max­i­mum of 95lb-in (8lb-ft). There is one more bolt head that

re­quires a smear of sil­i­cone un­der its head un­der the clutch at the edge of the sump open­ing. There are some more 6mm bolts on the top crank­case so once all had been tight­ened up on the bot­tom case, I turned the en­gine over and in­stalled these bolts, omit­ting to at­tach the cable guides. Be­cause this is a cus­tom bike, there was no guar­an­tee that the ca­bles would run as stan­dard so I de­cided I would ad­dress those later. I fit­ted the kick-starter re­turn spring and its alu­minium guide. I then re­fit­ted fourth and fifth gear se­lec­tor forks with their shift rod. I’m not go­ing into the gear­box build in much depth be­cause it is, in my opin­ion, an easy job, pro­vid­ing you read the proper work­shop man­ual, which can be bought sec­ond-hand off places like ebay or down­loaded free, if you don’t mind in­fring­ing copy­right laws. What is im­por­tant is that you as­sem­ble each part EX­ACTLY as dic­tated in the man­ual. Some gear­boxes e.g. BMW R100 gear­boxes can be a tad tricky as you have to cal­cu­late shim sizes etc. While they are not com­pli­cated in real terms, they can be a bit chal­leng­ing. Hor­i­zon­tal split boxes like Z1000s are a piece of cake. My first job next month is to dis­as­sem­ble the oil pump to en­sure it is healthy enough to de­liver a good dose of oil which will be needed to keep this fire breath­ing mon­ster healthy.

The orig­i­nal bike from way back when...

Re­mov­ing the top-end studs.

If you break a tap off you’ll be pay­ing a man with some special gear to save your arse!

The crank-shaft com­po­nents once re­assem­bled have to be welded-up for an en­gine of this power.

Clean­ing out all the tapped holes is a must, but you need to be very care­ful, even though it is a te­dious job!

You can see how long ago this ex­tra screw was sheared off by a numpty with no torque wrench. The break is rusty.

DON’T use cheap ex­trac­tors like the prover­bial Easy­outs.

The tool­maker’s but­ton is in­serted in the hole and cen­tres the drill in the bolt re­mains.

Not ideal, as they should be hard­ened, but I knocked up some tool­maker’s but­tons on the lathe, to get me out of a hole.

In­sert­ing a good qual­ity screw/bolt ex­trac­tor. A tap with a small en­gi­neer’s ham­mer will help the ex­trac­tor to bite.

Gen­tly turn the ex­trac­tor anti-clock­wise, en­sur­ing it is per­pen­dic­u­lar with the face.

A zed bot­tom-end is fairly sim­ple and se­ri­ously heavy-duty, which is handy for this power...

Weight is re­moved to bal­ance the crank by drilling shal­low holes in the webs. Note the high ten­sile studs.

The kick-starter spring in­stalled.

How about that – the hole was bang in the mid­dle!

Suc­cess! The lit­tle sod came out! To say I'm chuffed is an un­der-state­ment.

The crank-shaft com­po­nents, once re­assem­bled, have to be welded up.

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