Date of publication: 2018-03-10 15:30
The first three years of the KDX255 came with the model designation “A”—A1 through A8. Whenever there was a major revision to the line, the letter designation changed in a way that made little sense to the consumer. The next 255 in the series was the 1986 KDX255 C1 there was no “B1.”
Suspension action was still soft, keeping the KDX down in the enduro and trailbike category unless the owner invested in stiffer springs front and rear.
The next major change came after three years of the “C” series KDX, and that was the KDX255 E1. In it, two of the most lusted-after changes were incorporated, and of course those two were a liquid-cooled engine and a rear disc brake. Finally the KDX was lifted to the level of the motocrossers of the time, and magazine testers asked the question, “Who could ever ask for more in an enduro bike?”
And this included sub-par suspension units. The Kawasakis were notorious for coming from the factory with less than an ideal amount of oil in the forks, and they were also sprung for fairly lightweight riders. The stock forks were easy for an aggressive rider to bottom out, and so was the rear end, depending on rider weight. In spite of this, the KDX was a brilliant handling bike. Once the suspension was set up with the correct springs for the rider’s weight, and the fork oil level was set correctly, no one could dispute the handling superiority of the KDX.
Careful cylinder porting and attention to compression ratio, carburetor jetting and all the facets integral to feeding fuel into the engine were guaranteed to bring more power out of the KDX engine. Jeff Fredette was (and remains) the sole expert along these lines. He is still quite capable of taking a “vintage” KDX and making sure the engine will humble most modern liquid-cooled bikes of any brand.
yo da man MX GUY, I always do the work on my own bikes but that was when everyhting was a 2 stroke, the manual helped alot when it came to taking apart the motor,. Thanks Man
Less exciting, but possibly more important, is the improvement in the gear ratios in the 255 versus the KDX175. Jack Penton and the True Sport riders, along with engineering help from Tom Penton, tested and worked out gear ratio numbers that made the KDX virtually flawless as it was worked up through the gears. The combination of good, ridable power output as well as a sensible progression through the gears made the KDX hard to beat.
First off, cooling the engine of a trail bike was a different matter than cooling a motocrosser. Enduro and trail bikes had to occasionally crawl through airless woods and rock gardens where slow-going was the only way to survive. That’s where the riders took them, and the new liquid-cooled KDX overheated dramatically. It would be a couple years before coolant flow was improved enough to reduce the troubles with boiling coolant, and in the mean time accessory companies were creating all sorts of special anti-freezes and cooling system fixes, not just for the KDX but for all water-cooled bikes of the time.
Looking back, handling and suspension on the KDX was a curious mix. Reading all the test reviews of the time, a common consensus comes out: The suspension components were nothing special on the early KDXs, but the chassis design carried the KDX to the top of the class with ease.
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