YAMAHA YZF-R6

Ralph Fer­rand ser­vices a 20-yearold su­per­sport ma­chine.

Classic Motorcycle Mechanics - - CONTENTS -

Last month I pulled the calipers from my new ‘clas­sic’ Yamaha YZF-R6 and gave them a much over­due re­build. The Blue Spot calipers fit­ted to my R6 are leg­endary for their ef­fi­ciency, but af­ter a first test ride I was rather un­der­whelmed and felt that some­thing was very awry: the con­tents of the hy­draulic cir­cuit was some­thing akin to toxic waste and the R6 was sport­ing the orig­i­nal brake lines it left the Iwata fac­tory with. Many peo­ple don’t re­alise that rub­ber brake lines should be changed ev­ery four years. If you buy a bike with rub­ber brake lines, it’s al­most cer­tain that they will be the orig­i­nal ones, be­cause the in­fe­rior OEM rub­ber lines are usu­ally con­sid­er­ably more ex­pen­sive than an up­grade to stain­less steel braided lines, which are of­ten life­time guar­an­teed. First job was for me to re­fit the rear caliper. The brake pads are fit­ted on the caliper mount­ing bracket. As al­ways, I painted the backs of the pads to­gether with their anti-squeal plates and the parts of the caliper car­rier that the ends on the pads slide on with a cop­per based anti-seize com­pound. I fit­ted the caliper body over the pads and se­cured it in place with the slid­ing pins that are threaded into the caliper. I also treated th­ese to some cop­per slip which is the All-bran of the work­shop – it keeps parts mov­ing. I fit­ted the new HEL Per­for­mance stain­less braided line to the rear. The kit comes with new stain­less steel banjo bolts and cop­per crush wash­ers and the lines are avail­able in a ver­i­ta­ble rain­bow of

colours. Not be­ing a taste­less fool, I used black lines with pol­ished stain­less fit­tings which look nice. One cus­tomer, who shall re­main name­less (you know who you are) in­sisted that I fit bright green lines with gold fit­tings to his Kawasaki ZX-6R. I re­ally wished, as I fit­ted them, that I had not opened my big mouth about the colour op­tions avail­able; not a mis­take I’ll make again. He fur­ther vul­garised the bike with gold an­odised trin­kets be­fore to­talling it through pi­lot er­ror, which made a mock­ery of the life­time war­ranty his lines came with. It’s quite im­por­tant to torque th­ese banjo bolts cor­rectly, as you need enough pres­sure to crush the cop­per wash­ers, but not enough to strip the threads. When it came to bleed­ing the rear, I found I had some air trapped, so I un­did the caliper and held it up. That al­lowed the big boy’s Mi­ty­vac to suck it out the bleed nip­ple. I then turned my at­ten­tion to the mighty Blue Spots up front. As with the rear, I fit­ted brand new stain­less bleed nip­ples and sealed the threads with PTFE tape to stop the vac­uum brake bleeder suck­ing air in through the threads. I bolted both calipers to the fork legs with a drop of thread lock and seal on the mount­ing bolts and fit­ted the new braided lines. I filled the mas­ter cylin­der reser­voir with fresh brake fluid and then bled the sys­tem with my vac­uum brake bleed­ing kit. It re­ally is the eas­i­est way to do the job. Just open the bleed nip­ple and keep suck­ing the fluid through un­til there are no more bub­bles com­ing through in the fluid ex­it­ing the nip­ple. Do keep an eye on the reser­voir though, be­cause if you com­pletely empty it you’ll start suck­ing air through, which will take you back to square one. Once the brakes had been pumped up and I had a nice firm lever, I topped up the reser­voir to the top mark. As the pads wear, so the level will drop a lit­tle. Be­fore re­fit­ting the cap and its lock­ing parts, I checked the fluid con­tent and was sat­is­fied to see zero wa­ter in it. Now the brakes were fight­ing fit, it was time to make the en­gine run smoothly. Given the pre­vi­ous owner had not had the carbs bal­anced since own­ing the bike, it seemed this was the first place to start to ad­dress the lumpy tick-over. Be­cause this bike uses a fuel pump, I wanted to see if I could get away with­out us­ing an aux­il­iary fuel tank. Be­cause I have a scaf­fold tube sus­pended from the work­shop ceil­ing, for a hoist, I at­tached a light rope to the front of the tank and at­tached the other end to the scaf­fold tube which held the tank out of the way while I worked on the carbs, but would still carry on its job of sup­ply­ing fuel. The vac­uum take-offs for th­ese down-draught CV carbs were not the eas­i­est to spot. Af­ter read­ing the words of Mr Yamaha, I dis­cov­ered that there are four pipes run­ning from very in­ac­ces­si­ble parts of the carbs and the ends are joined with two odd dou­ble ended blanks in pairs – see the pho­tos. To syn­chro­nise the carbs you un­plug all four pipes from the ‘blanks’ and plug them into the req­ui­site vac­uum gauge pipes. Both the Haynes and fac­tory man­u­als make light of ad­just­ing the syn­chro­ni­sa­tion screws found be­tween each pair of carb bod­ies. Nei­ther man­ual in­forms you that th­ese screws are dif­fi­cult to lo­cate and re­quire some form of fin­ger con­tor­tion to get a screw­driver onto said screws. Maybe I am just not used to work­ing on such modern bikes. The worst by far I have worked on was a Honda CBF600N.

For this I had to use a spe­cial an­gled car­bu­ret­tor screw driver and had to kill the en­gine and turn the throt­tle most of the way around to get the screw­driver on the ad­juster be­tween 2 and 3, make the ad­just­ment, restart the en­gine, see how it looked on the gauge and re­peat un­til in bal­ance. It took ages and much cast­ing of doubt upon Mr Honda’s parent­age. Again the dif­fi­culty of mak­ing the ad­just­ments was glossed over by the fac­tory man­ual au­thor, pre­sum­ably not wish­ing to high­light the crap de­sign! As with all carbs that are bal­anced be­tween pairs, I bal­anced 1 and 2 then 3 and 4 and fi­nally 2 and 3, which is ef­fec­tively bal­anc­ing the left-hand pair with the right-hand pair. I soon had all the carbs in tune with one an­other’s chakra and the en­gine sounded all the sweeter for it. An­other mat­ter that nei­ther man­ual men­tioned was re­mov­ing the air-box for this task. The Haynes pho­tos of the op­er­a­tion did show the air-box was re­moved, but like the fac­tory tome ne­glected to men­tion it in the in­struc­tions, which is odd con­sid­er­ing both felt the need to tell you that you should re­move the tank. I dis­con­nected the mighty Vacu­um­mate hoses and re-plugged the blanks into the pairs of vac­uum take-off pipes and re­assem­bled the air-box to­gether with the ducts that feed it with air from the front of the fair­ing. Though the air-fil­ter is a wash­able foam type, I binned it and gave it a new one. With foam fil­ters, you need to oil them be­fore use and typ­i­cal to form, I slipped and well over-oiled mine and spent ages try­ing to ex­tract the ex­cess, which is why the new one in the photo looks a tad grubby. From a work­shop per­spec­tive, I far pre­fer pa­per el­e­ments; they’re so much eas­ier to work with – you bin the orig­i­nal, un­wrap the new and stuff it in the air-box, job done. Were I not so mean I’d have bought it a nice K&N, but even at trade rates, they cost a lot of beer to­kens and writ­ers need beer. Modern air-boxes are very com­pli­cated com­pared with the items on old bikes, not least from all the en­vi­ron­men­tal re­quire­ments leg­is­la­tors pile upon man­u­fac­tur­ers th­ese days. In the old days the eas­i­est way to get more power from your bike was to re­move the air fil­ter al­to­gether and fit bell mouths and if your en­gine was very lucky, the mouths of said air trum­pets would be gilded with a coarse wire mesh to keep out small mam­mals and birds. The old Bri­tish par­al­lel twins of the day had to have their en­gines stripped and re­built with aw­ful reg­u­lar­ity any­way, due to poor qual­ity ma­chin­ing of the parts in the first place.

Then came the more re­li­ably, ac­cu­rately built Ja­panese bikes of the ilk of the CB750 Four and the mighty game chang­ing Z1; and so folk took out the far more so­phis­ti­cated air-boxes, and re­placed them with K&N or S&B pod fil­ters which had su­pe­rior air­flow over the stock pa­per el­e­ment and (un­like the old bell mouths) did ac­tu­ally fil­ter the air go­ing into the mill. The main prob­lem was that the home ‘tuner’ of­ten had lit­tle or no un­der­stand­ing of the ef­fect of their ‘up­grade’ to fuel air sys­tem of their bike, which when mixed with a 4-into-1 pipe, with the baf­fles re­moved, made lots of noise, but screwed up the car­bu­ra­tion a treat. The ef­fect of this was make the en­gine run ex­ces­sively lean, burn­ing valves and mak­ing the en­gine run hot. Some lads did un­der­stand that you needed to change the jet­ting, but con­sid­ered tak­ing the main jets up a size or two would cure the is­sues and it rarely did, as the mains only re­ally be­come a ma­jor player when you have the taps wide open. A pow­er­ful bike with a beau­ti­ful smooth power curve, may have gained one or two horse power at max­i­mum, but would have a lumpy power curve with loads of flat spots. Ledar pro­duced some correction kits back in the day that were fairly ef­fec­tive, but was un­able to cure the prob­lem of where the air was com­ing from. For per­for­mance you want as much air as pos­si­ble, but ide­ally you want to be suck­ing it in from still air and then through air trum­pets, not the very tur­bu­lent, ever-chang­ing air found be­hind a bike en­gine. Modern air-boxes ac­tu­ally have air trum­pets not dis­sim­i­lar to the trum­pets used on old café rac­ers and race bikes from yes­ter­year, which have their di­men­sions care­fully cal­cu­lated for per­for­mance and ride­abil­ity. In a per­fect world the air trum­pet length would change with en­gine revs and there­fore in­take air speed, but I had never seen this catered for, un­til I saw the very lat­est Nor­ton V4 en­gine at the last Mo­tor­cy­cle Live, which has vari­able in­let tracts. Be­fore you all clam­our for your writ­ing in­stru­ments, I am aware the Nor­ton is fuel in­jected, but the suck­ing of air fuel mix­ture into an en­gine is vir­tu­ally the same in both sys­tems. But for us oldies, who will never again be the right shape to get aboard a Nor­ton V4RR, nor have the re­flexes to fully ap­pre­ci­ate the 200-plus horse­power, nor the car­bon fi­bre chas­sis, it is im­por­tant to re­alise that if you want to get the best out of your clas­sic Ja­panese bike, keep the stock air-box and look in other di­rec­tions for more power if you re­ally feel you need it. The last job for this ser­vice was to change the oil and fil­ter, while the en­gine was still warm from the carb bal­ance. Seems sim­ple and in fair­ness it is, pro­vid­ing you fol­low a few sim­ple rules. When you drain out the oil, do so into a clean oil bowl, so that you can see if there is any­thing nasty in it. Most sump drain bolts have a crush washer, so AL­WAYS re­place it with a new one. When re­plac­ing the sump bolt AL­WAYS tighten it to the spec­i­fied torque set­ting given in the man­ual. Too loose and it’ll likely leak, too tight and you run the risk of strip­ping the thread in the sump, which can be a ma­jor pain to re­pair and not a job for the per­son who stripped it in the first place. If you don’t have a torque wrench, ei­ther buy one, bor­row one or give the job to some­one who does have one. AL­WAYS change the fil­ter when you change the oil. Oil fil­ters cost but­tons and their ef­fi­cacy is of paramount im­por­tance. I took the R6 for a ride but she is blis­ter­ingly fast – maybe bet­ter suited to the track – so I hope to be telling you how I got on at Cas­tle Combe soon!

The fat man squashes yet an­other de­fence­less lit­tle Yamaha.

Paint­ing some cop­per slip on the parts where the brake pads slide and on their backs.

Fit­ting the caliper over the pads.

Fit­ting the slid­ing pins.

Torque­ing up the brake line banjo bolt.

Ser­viced Blue Spot caliper ready to re­fit. Last month we showed you how to.

Torque­ing bolts when re­fit­ting the rear mas­ter cylin­der af­ter brake line swap.

I lifted the caliper to free some trapped air in the fluid. Yes, it seemed to help.

Tight­en­ing the caliper mount­ing bolts with an ac­cu­rate torque wrench.

Bleed­ing the left hand Blue Spot.

The tank sus­pended out of the way with some light rope. This en­abled it to be used with­out ob­struct­ing ac­cess.

Ac­cess to the syn­chro­ni­sa­tion ad­just­ment screws is not great.

All the vac­uum pipes con­nected to the vac­uum gauge pipes.

The lower joined pipes are one pair of the vac­uum houses con­nected to the in­let tract. Th­ese are parted and con­nected to the vac­uum gauges.

Now that is the ideal wa­ter con­tent of brake fluid: zero!

The dou­ble ended blank with one vac­uum pipe re­moved.

Get­ting there, very close.

Fit­ting a new oil fil­ter. It’s com­mon sense to do this if chang­ing oil!

Al­ways use a torque wrench to fit the oil fil­ter and sump bolt.

The lower part of the air-box in place.

Re­fit­ting the right hand air in­take duct.

The foam air-fil­ter cleaned and re-oiled.

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