YAMAHA YZR500
Niall Mackenzie has issues sorting the clutch.
The decision to give my YZR a full overhaul was mainly based on visual observations so it was no surprise that on closer inspection there was plenty more work to be done.
It started with brake fluid from the front master cylinder seeping down the righthand side of the nose cone melting the paint. Nothing can stop time taking its toll on seals, etc., so I knew there was probably much worse lurking beneath. If you follow my exploits in CMM you’ll know my go-to company for anything resto related these days is IDP Moto at Silverstone, so cue a consultation with boss man Daryll Young for expert advice.
With the bodywork removed we immediately saw some minor corrosion on the outer water pump casing and the cooling pipe that links the top two cylinders. My bike is an exotic animal, having lightweight magnesium crankcases and covers, but the downside is they’ll turn to dust if not looked after properly. This has always played on my mind and another important reason to bite the bullet and give this lovely bike a well deserved birthday. One end of the pipe was completely gone so we had a new insert expertly made up and then fitted and sealed with Araldite. There were also a few blowholes that we sealed from the inside.
On closer inspection the water pump housing was badly corroded, but fixable by skimming both surfaces and fitting a new gasket. You’ll see from the pictures that we also had a sketchy water jacket union at the base of the motor that needed the same treatment. All the other magnesium related parts, including the main cases, looked absolutely fine so we’ve put the damage down to the cooling system not being drained properly. And I should know better. After being presented with my
Cadbury’s Boost Yamaha YZF750 race bike at the end of the 1998 season, 15 years later I decided to give it a run out at the Steve Hislop Knockhill tribute event. I contacted my old crew chief Ade/ady Marsh for some expert advice on how to get her running and he said: “Assuming you drained everything in 1998 all you need is fresh fuel and water and she’ll be good to go.” Of course, you can guess that I hadn’t drained anything. Fortunately any fuel had evaporated and I changed the oil, but the water caused some minor, but repairable damage similar to the YZR. Needless to say my GP bike will be left thoroughly dry from now on and kept at room temperature.
With the motor still in situ, next up was a top-end strip down, which thankfully revealed all four cylinders, heads and pistons in great shape, including perfect light brown piston tops, indicating my carb jetting is spot on. Piston rings were always replaced before races to keep performance sharp. However, I haven’t come close to doing race distance since I acquired my bike, and I’m not about to race Kevin Schwantz any time soon so I feel there’s no need for unnecessary expense. While the cylinders were removed, we checked, cleaned and lubed all four powervalve bearings and mechanisms. We also removed the clutch for inspection and straight away could see the friction plates had seen better days.
I suspected some slight clutch slip on my last outing so this didn’t come as a big surprise. From memory as these plates were replaced the night before every race the lack of meat wasn’t a big shock. I’ve known for a long time that Padgetts of Batley have these plates in stock, but at £350 a pop (I needed eight) I’d never been able to commit. Having found no other options, I had actually psyched myself up to call Clive Padgett, but God intervened and a miracle occurred.
Just a month after I decided to go ahead, Daryll from IDP had a chance meeting in Spain with an ex-mechanic of Juan Lopez Mella, a Spanish privateer rider who raced in GPS in the mid-90s on a ROC YZR 500. I remember him well as he scored points in a few of the 1993 GPS, but sadly lost his life in a 1995 car crash on his way to a race. Daryll got talking to his mechanic Jose Clemente in Valencia and they inevitably started talking about racing. Turns out the wee Spaniard had a brand new complete clutch in the back of his van that he was willing to sell. With both parties knowing these things are as rare as an honest politician, we agreed on a price of £1500. Steep I know, but the friction plates alone would have been £2800 from Padgetts.
A little back-to-front I know, but with everything reassembled and fresh gearbox oil added, we removed the motor then completed the strip down by removing the swingarm and head-stock before stripping everything down to the last nut and bolt. Thankfully, from this point on there was nothing else too expensive that needed replacing so it was just a case of cleaning, checking, lubing, servicing and rebuilding. While in the Valencia Moto GP paddock we were able to access the Nissin brake service outfit, who kindly serviced my rear Nissin brake master cylinder and caliper. The Uk-based Brembo team did the same with the front stoppers and also supplied new 320mm front discs to replace the original carbon items. The carbon discs are ok, but they do give a slight ‘pumping’, a tiny feeling, but something I wanted to avoid. As I’m planning to use the bike it made sense to make the swap to more conventional rotors. That’s because I’d prefer to avoid any involuntary stoppies that so easily occur with ham-fisted riders and grabby carbon brakes. It goes without saying that new fluid was added along with new seals and brake lines. As suspected, the leaking master cylinder that prompted the whole adventure was purely down to seals disintegrating over the past 20 years.
I have to admit our official Ohlins technician who was enlisted to check over and service my suspension revealed a surprise. It turns out my rear spring was actually a Yamaha part painted up in Ohlins yellow. Apparently this was common back in the day as many suspension parts were made and tested by Yamaha in Japan, then found their way into the GP paddocks. Although out of sight, much of the spring was also pretty scabby so after coming this far I chose to replace it with the real deal from Sweden.
Next time it’s the final phase, plus I should have her fully assembled and looking even more immaculate than the day she left the Yamaha race department in Hamamatsu. Stick with me!