Ralph Ferrand services a 20-yearold supersport machine.
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.