What: Kawasaki KLX250 Special
When: August 1996 Issue No. 203
Purpose: Thumper Nats and motocross
How Much: No price given
After ADB ran a picture of the Japan only KLX300 people wanted to know if and when we might see it in Australia as the combination of more punch in a 250 frame had been well proven by machinery like the Ballards Honda XR280 and Webby’s Motorcycles Yamaha TT300R. This left the Kawasaki fans in a bit of an awkward spot so Murray Tainton of BTX Motorcycles stepped into the breach and having long experience of building special Kawasaki’s he decided to see how far he could go. He started with a KLX250 and ended up boring and stroking it to a capacity of 345cc’s to make the machine you see here and did a little extra work on suspension and graphics just to complete the job.
At the time of printing there were still a few bugs to be sorted out as the bike had lunched itself at the first round of the ADB Thumper Nats but little problems like that don’t discourage someone like Murray. The process was started with a 300cc Nikasil coated barrel, a part that was available on a changeover basis for $610 in those days and gave a good increase in power, but Murray was chasing more so the next step was to stroke the motor. This involves a lot more than bolting on a bigger barrel and to increase the stroke by 9mm the crank pin offset needed to be moved by 4.5mm, a time consuming process to do properly. That though is only half the story as a 9mm spacer was then needed to lift the barrel so the piston didn’t try and ram its way through the head at TDC and the bottom of the rod needed shaving to clear the engine casings.
The next step was to machine the flywheel and counter-balancer gear for clearance bearing in mind nobody had done it before so it was all pioneering work. To make the most from the extra capacity and achieve a broad and strong spread of power some hot cams were added to the mix along with heavy duty valve springs, matched ports and a DR350 carby bored out to 36mm. The airbox lid was removed, a White Brothers Megalloy muffler was added to the standard pipe and it was fuelled with premium unleaded mixed with 15% methyl benzine. Suspension springs were left standard as Murray was only a little bloke but he worked on the damping and filled both ends with five weight oil then a Pro Circuit lower linkage raised the back end slightly, quickening the steering due to a steeper steering head angle and also increased travel a little.
The DR350 carb meant some frame modification was needed to make it fit, a Gunnar Gasser Whirpool throttle was added, a taller seat with firmer foam, white radiator shrouds, purple Takasago rims, the front number plate and disc guard from a KX250 and a KDX200 front mudguard completed the picture. The final result was a mighty quick sub-400cc bike with a broad spread of power that loved to rev making it easy to loft the front wheel, power out of the gate or blast out of a berm and it got the power to the ground in a user friendly way. BTX motorcycles could build more for anyone with the time, patience and money but it was never meant as a commercial venture, just an experiment over 12 months to see how much could be extracted from a KLX250. The more cost effective solution for Clarence Clubman would have been the over the counter 300cc kit.
