THIS BIKE HAS SEEN LIFE.

In fact, it's seen a typical sportsbike's life several times over. Ridden everyday through the winter, toured at high speed, two-up to Morocco, been fitted with a Hindle exhaust, a K&N filter and a Dynojet kit and generally ridden hard - as it's designed to be.

But right through all this, the bike has been regularly cleaned and serviced (using genuine Kawasaki oil filters and semi-synthetic oil). At 18,000 miles it was still on its original chain and sprockets, such had been the care that long-term tenant Rob 'Bertie' Simmonds had lavished upon the ZX-9R.

But when Bertie left Bike, with his ZX-9R showing 25,000 miles, we took the opportunity to dismantle his pride and joy, bit by bit, nut and bolt by nut and bolt. Where we found corrosion, we noted it. Where we found wear, we did the same. By the time the ZX-9R was in several hundred pieces, we had a good idea of how well, or otherwise, that Kawasaki build bikes. Remember that this bike has been subjected to salty roads, dyno runs, speed tests and journalists.

Of course, we needed independent, trustworthy engineers to assess just how good, or bad, the Kawasaki was looking after all this. For the motor we chose Dave Stephenson, a veteran engine builder who has built TT winners, spent many years as personal mechanic to such riding gods as Nick Jefferies and Phillip McCallen, and spent a year contracted to the Castrol Honda team. He's talented, experienced and utterly unwilling to say anything except what bethinks, regardless of politics.

For the suspension, we chose James Campbell-Wilson of Set-up Engineering, who analysed the wear, advised us how to re-set preload, rebound and compression settings and winced at the settings that we'd been running. 'All wrong, even for a fat bloke,' is a rough summary of his commentary. So read on for the most comprehensive analysis ever of modern bike wear and corrosion. There are a few surprises.

Cylinder head

Before the engine was stripped, Dave performed a leak-down test on it. This is to check how well valves and pistons are sealing; what it revealed was that the valves were sealing well but there was a slight leak past the piston rings. The reason for that was revealed when the engine was stripped.

Next, though, Dave measured the valve clearances: four of the three inlet valve clearances were too small and four of the eight exhaust clearances were also too small. That happens as the valves hammer their way into the cylinder head, and is perfectly normal, considering that the clearances weren't a long way out of tolerance, and the engine was due for a service.

So then the engine was stripped down, and the head whipped apart. The few marks found on the camshaft bearings are normal, and probably occurred within the first few miles. The camshaft is only lightly scuffed - again, completely normal - and the valve stems are virtually unworn.

In the cylinder head, one valve had started to pull a bit too deeply into its seat, probably due to the valve clearance being too tight, and the exhaust valve seals were just beginning to let oil through - not enough to cause blue smoke, but oil consumption would have increased slightly. All acceptable for 25,000 miles.

Pistons and bores

The reason for the leakage past the piston rings became clear when the cylinder bores were examined: they were glazed (i.e. shiny rather than matt) so the piston rings weren't bedding into them. There are various possible causes of this: overly careful running-in, use of too high a quality of oil (probably synthetic) during running-in, or just a very hard thrashing at some point. A quick run through with a honing tool will sort it out.

There's also light scuffing on the edges of the pistons, which is likely to have been caused by starting the bike and revving it hard after it has been standing for several days (long enough for the oil to drain away). Rob's habit of revving the engine just before switching it off won't have helped, because that last blip of the throttle sends neat fuel into the cylinder, washing away the oil. Despite that, there's no discernible wear to the cylinder bores, pistons or piston rings: they're well within tolerance. They look as if they'll go on forever.

Bottom end

Here's where it gets interesting. As the crankshaft came out, we found a real problem: one main bearing was in trouble. On the end furthest from the oil pump, the two halves of the bearing shell had a lightly gouged groove through the centres, and fragments of bearing metal deposited on the shells on either side of the groove.

Dave measured the wear in the bearings using plastigauge (you'll see the red remnants of it still on the crankshaft journals). All were within service limits, except for that gouged end bearing, which was just outside the limit. The big-end bearings were fine too.

So what about that rogue main bearing? Talks with Dave, Kawasaki and a commercial metallurgy laboratory provided the most comprehensive and feasible explanation. On the back of each bearing, the outlines of the bearing housing are clearly reproduced, meaning that the bearings were seated extremely well. But on the damaged bearing shells, the outlines are nowhere near as distinct - evidence that they weren't seated quite right, from new. That would have pushed the bearing shells closer to the crankshaft journal, causing the first, soft layer of bearing metal to be scraped away on the tight sections, and redeposited where there was more clearance available. That first layer of bearing metal is designed to do just that, as well as to protect the next copper-based layer from attack by any acid in the engine oil.

So the bearing damage we found wasn't ideal, but it wasn't a disaster either. The metallurgy lab were adamant that it wasn't caused by tired oil, or abuse (you can rest easy Bertie), and that the bearing wouldn't have failed prematurely.

Oil/water pump

The ZX-9R's oil pump is neatly combined with the water pump: and nicely made with it. The water pump fins seemed to be of unusually high quality, so there's not a trace of corrosion on it. As for the oil pump side of it, there's negligible conventional wear, but it looks as though a piece of swarf or maybe even sand (from Morocco perhaps) has been carried round it at some point, leaving score marks that could have caused a slight drop in oil pressure -which might account for the wear to the camshaft buckets.

Clutch

Late last year, the ZX-9R was speed-tested at Bruntingthorpe for the second time in its life. If there's anything that will finish off a clutch it's the acceleration tests, and sure enough the ZX-9R's metal clutch plates are blue and black from heat. Incredibly, those plates haven't warped and the friction plates are also still within service limits. Even the clutch basket, which the plates sit in, has only light marking on it: after 25,000 miles many clutch baskets would have deep serration's along their edges. That's one tough clutch. (I am not sure I would quite agree on that - Kev)

Gearbox

The ZX-9R had started to jump out of gear very occasionally. The reason became clear once it was stripped down - the edges of the engagement dogs had rounded off. This is common at this kind of mileage, especially if a bike has been subjected to loads of unsympathetic, clunky gearchanges (clutchless or not). Our ZX-9R gearbox has probably got another 10,000 miles in it, after which it will be best to buy a low-mileage gearbox from a breakers.

Brakes

The front discs are almost down to their service limit, with a few choice grooves thrown in for bad measure. Another 1000 miles and they'll have worn to their minimum permissible thickness - but that's nothing to be ashamed of after 25,000 miles. New discs will cost 100-odd each. The calipers and their pistons looked horribly grimy, but they wiped clean to reveal uncorroded metal - not always the case with Tokico calipers.

Front suspensionThe front fork sliders were showing signs of their hard life, and the fork seals were leaking. James Campbell-Wilson of Set-up Engineering stripped the forks, to find the fork oil had oxidised and turned to sludge: a typical problem. That sludge forces its way past the seals, hence the leaks. The forks were cleaned out, and the scratches and pock-marks on the fork legs were removed in a lathe, leaving a cross-hatch finish on the legs

that will reduce stiction. On rebuilding, James filled the forks with 5W Putoline oil, leaving an air gap above the oil of 135mm. Preload was set to 4V2 rings showing, with rebound damping set to 10 clicks off minimum and compression set to nine off minimum.

A full 'race' service like this on a set of forks by Set-up Engineering will cost £150: without the cross-hatch refinishing it would have been £112. Head bearings are sometimes found to be too tight on these big Kawasakis, but ours were fine.

Rear suspension

The first fault typical shocks suffer from is a lack of pressurising gas in the remote reservoir, which slows the rebound damping. The result is that the bike feels likes it's trying to kick you out of the seat over big bumps. James found that our shock was part-empty but, rather than replace it (between around 200 and 650), he drilled out the reservoir's valve cap re-filled it with gas to a pressure of 14 Bar (it's usually 10 Bar) and re-capped the valve. The rebound was set at 21 clicks off minimum and compression at 14 off minimum. The complete service was £80: double that if you leave Set-up to remove the shock from the bike.

The swing-arm and suspension linkage bearings are still smooth and free of play. When it's put back together, the suspension sag, front and rear, will be set at 9mm.

Conclusion

After initial horror at the state of the main bearing we were placated by the closer examination, which assured us that the bearing wasn't about to give up altogether. But it is far from ideal having a bearing in that state, even though the rest of the engine is in an excellent state. Aside from the bearing, the build quality of the big Kwak is excellent. There was a point last winter when we worried that it was starting to deteriorate, but Bertie's conscientious cleaning surely saved the day. The result is that, despite salt and every other nasty that British roads throw at a bike, our ZX-9R still looks remarkably good.