Wednesday, March 12, 2008


The sins of the previous owner

As many of you know, I reached the end of an 8-year search last spring when I finally found the right Kawasaki ZRX, and snatched it up into my stable. Since then, the past nine or ten months have been absolute coolness -- spiritual, even -- as my Z-Rex and I have become acquainted with one another. I'm proud to say, with much admitted bias, that I own one of the most fantastic motorcycles ever produced.

But there was always one small problem with my particular Rex that I could never solve. No matter what I did, achieving a suspension setup I was happy with constantly eluded me, sometimes almost mockingly it seemed. From front to back, top to bottom, I went through every possible suspension configuration you can imagine. Throughout the entire system, I made adjustment after adjustment in an attempt to dial-out a strange vagueness in the front-end feedback that I just didn't like. Now mind you, there wasn't really anything outrightly "wrong" with the way the Rex rode or handled. It was stable and responsive. But at the same time, it was never what I considered to be totally "right" -- and it certainly wasn't anywhere near what I felt convinced the bike was capable of. This is hard to explain, but the front felt heavy and "teetery" and low speeds, but overly light and dodgy at high speeds with a tendency to right itself. I was baffled.

So at one point late last summer, I basically gave up on dialing the bike in, resigning myself to the fact that it wasn't a full-on track bike like my ZX7R and ZX6R, and that it would never feel as perfect. It was a retro-style '80s hooligan bike, by golly, and I'd just have to live with mediocre handling.

Then, just last week -- as I began contemplating the possibility of biting the bullet completely and lowering my Rex to dragbike height -- I made a forehead-slapper of a discovery on the rear shocks that explained everything.

The tabs that hold the rear preload adjusters in place had been removed by the previous owner and the rings were being held by a set of secondary retainer castings higher up on the outer cylinder:

By my best measurement, this lowered the rear ride height somewhere between 15 and 20 millimeters. In and of itself, not an inherent problem. But get this, the previous owner left the front ride height in stock configuration!

"No wonder this thing handles like shit!" I literally yelled out.

So last night, after some rough calculations and experimenting, a friend and I lowered the Rex's triple clamps a total of 19 millimeters on the fork tubes. As soon as I rode the thing, I found what I had been missing handling-wise over the past year. The top-heavy, teetery feel is gone at low speeds, and the bike fires into turns willingly and without protest at speed.

Subsequently, I adjusted in a little more rebound force up front and will probably still make some changes to the front preload, but right now, it's like I bought a new bike. It's still no bullet train like my 7R, and I obviously lost some ground clearance and sacrificed the overall optimum geometry by going lower, but still -- it's literally twice as good as before.

The lesson: When buying used, don't assume the previous owner had any idea what he was doing. Go over everything with a fine-tooth comb and pour over the shop manual. If I had been more thorough in the beginning, I could've had this aggrivation licked a long time ago.

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