The KTM is nearly ready to go. At least it is ready to go ride after a complete overhaul. While all of the final race prep is not yet completed, it is ready to go do some testing in the desert. This is my 1992 KTM 250exc project that I am building to compete in the 2011 NORRA Mexican 1000 race.
The Mexican 1000 is a vintage race for all two and four wheeled vehicles that spans the Baja Peninsula. The three day stage event revived many of the older vehicles that once competed in the race in years past. I participated last year, riding with Baja legend Ron Bishop on a 1985 Husqvarna 500xc. As the rules have advanced the minimum age this year, I have chosen a bike a little closer to my heart to compete on.
I will be riding in the late model light weight class. I think the KTM is going to be the perfect choice. It has many components that are direct ancestors to today’s bikes. The two stroke motor is not that far removed from current bikes. As you will see, KTM kept so many parts the same that we were able to bolt on some significant updates with little or no additional modification required.
I expect that the large displacement class for motorcycles will be dominated by Honda XR600 models. Yet, with word of Larry Roeseler’s entry, I would expect to see a great old Kawasaki KX500 entered also. For my part I considered a number of different bikes to use such as a Kawasaki KDX200 and Honda XR250. As I am a KTM rider at heart this bike was the one that I finally decided upon.
When I first purchased this bike I was pleasantly surprised to find that nearly everything was in very good running condition to start with, $1000 well spent. As I spent more time with it, riding and getting the general feel for what modifications to make, I became even more in love with it.
One of the great things about KTMs it that many parts are interchangeable over a large span of years. For example, the rear wheel is the same on nearly every bike from 1989 to 2011. So I won’t have to source any spare wheels. Many other spare parts that I have cluttering up the garage will fit on this bike also.
First on my list of improvements was the suspension. The stock parts actually work very well and have a modern feel. The front fork is a little harsh on the high speed compression. Javier at Trail Tricks suggested a revalve and general freshen up on everything.
I consulted with Tom Moen at KTM about what suggestions he had for the bike. Tom was heavily involved in the original R&D of this model. His primary suggestion was to update the SEM ingnition to something more modern and reliable. He also figured that a V Force Rad Valve should theoretically be able to bolt right on in place of the original reed block. Sure enough, using a collection of old parts from KTM and Trail Tricks, we were able to bolt both modifications right on. This should help with engine response and clean up the jetting significantly.
As part of the Rad Valve, we installed a spacer plate to increase the crank case volume. This will give the motor a beefier bottom end response. With the Kokusan 2k2 ingition we were limited on the size of flywheel that would fit inside the stator cover. This set up is much lighter than the original SEM flywheel on the exc.
It took a little work to figure out the mounting for all the parts up under the tank. We had to fabricate brackets for the black box, coil and voltage regulator. But once done, it all fit in quite nicely. If I would take the time to clean and paint everything it would look just like a factory installation.
Other mods include Fastway footpegs, Flexx Bars, Scotts stabilizer mount and fat bar conversion, no toil air filters, Motorex Crosspower 2t oil, Progrip grips. I was able to find NOS graphics and seat cover on Ebay.
Trail Tricks did all the motor work. Other than the work I have described it is basically all stock inside. When I bought he bike it had a newer generation Keihin PWK carb instead of the original PJ unit. So here is a look at all the work we have done so far: