This week we got to ride Ralf Schmidt’s brutal 500cc two-stroke project. It’s a Honda CR500R motor in a current TM 300 chassis. He calls it TMZilla. Heck, why not? You put “Zilla” on the back of any word and it says something about going overboard. When the project was first assembled, we featured it on Two-Stroke Tuesday. Now, we finally got a chance to ride it.
Ralf found the Honda 500 on Craigslist and started on the project over a year ago. We have discovered over the years that dumping a Honda 500 motor into just any modern new frame isn’t always a good idea. The early Service Honda AF500s with first-generation aluminum frames didn’t handle as well as an original CR. There was something about that first aluminum frame, which was very rigid, and that motor, which was very shaky, that didn’t get along. Since those early AF500s, the knowledge pool of mixing and matching CR500s in updated frames has grown considerably. The current TM250 frame turned out to be a good match. Two brackets needed to be moved, and the cylinder, carb and airbox lined up perfectly. The Scalvini pipe needed only slight modification. GET DIRTY DIRT BIKES did all the welding jobs on this project. The oversize aluminum tank from the ’08-’14 TM 2-stroke ended up being a perfect match and gave the bike to have enough fuel for a GP race. He used a Lectron carb, Boyesen reeds and cases and a ProX engine rebuild kit.
When you ride any CR500, regardless of chassis, you have to overcome your initial fear of starting the bike. This was never that big a deal back in the old days, but the technique is in danger of being lost to time–kind of like curing leather with whale blubber or enduro time-keeping. You have to get the piston in just the right spot, just past the point of most resistance. Then bring the lever all the way up and kick like you’re angry. The slow, even four-stroke technique won’t cut it. You have to have a lot of downward foot speed while you blip the throttle just right.
It turns out that the TM chassis was a good match to the 500 motor. Our fears that it was too rigid were unfounded. TM frames have been evolving along with the rest of the industry, and the modern KYB fork and TM shock were perfectly valved by Noleen Racing. Mark Tilley was never a 500 rider back in the old days, but recently, he’s become a big fan. “I think I would have loved these if I had been racing 30 years ago! You just kind of growl around the track. It’s sort of how I ride anyway.”
The bike still has all the hallmarks of a CR500, both good and bad. It vibrates–there’s no getting around that. It also requires that you think ahead and plan out your lines. When you do it all right, the TM500 isn’t fearsome to ride at all. There’s something almost soothing about it. You can read more about the TM 500 project in the August 2020 print edition of Dirt Bike.
ZACH BELL’S CHOICE
We went out with Zach Bell and the Precision Concepts race team this week to check out Zach’s preparations for the two-stroke Championship, which is now scheduled for October. Zach won this race in 2018 when he was riding for Husqvarna, but defending his title was a challenge after switching to the Precision Concepts Chaparral Kawasaki race team. Husky had a current two-stroke for the using, whereas Kawasaki hasn’t made the KX250 in 13 years. For that race, he borrowed Justin Seeds’ bike and worked like crazy to get it ready. The bike was beautiful, but the whole project was a little too rushed, and he ended up breaking down.
This year’s project is a little more conservative in its approach, but Zach, Phil and Bob are way in front of it as far as testing goes. The bike belongs to Scott Perkins of District 37. It was pretty rough to start with, but its coming together well. You can read a little more the Zach Bell 2007 KX250 two-stroke project here.
We got to talk with Zach about switching back and forth from two-stroke to four-stroke. He clearly enjoys riding the two-stroke championship, but the bike is very different. “It’s pretty fast, but the hardest thing to adapt to is the lack of engine braking,” he says. “That changes the way you have to ride the bike. It doesn’t rev nearly as high, either, so you have to think about what gear you’re in all the time. I like how light the two-stroke feels.” Are there any races where the two-stroke would be an advantage over his regular KX450? “It depends on the course. The Sprint Enduros we ran last year are a little too wide open, but if they were tighter and more technical, it would be better for the two-stroke.”
250 2-STROKE SHOOTOUT IN PROGRESS
We currently have a 250 two-stroke shootout in progress. The bikes are the KTM 250SX, the Husqvarna TC250, the TM 250MXE and the Yamaha YZ250. We don’t get to do this every year, so it’s a treat; everyone loves riding these bikes! Last week I offered a few impressions on the TM 250MXE, and now it’s only fair to tease the KTM 250SX as well. Spoiler alert: this bike is the favorite going in to this test. It’s the lightest and it’s probably the fastest.
On our scale, the 2020 KTM 250SX weighs 214 pounds without fuel. That’s a pound lighter than the Husky and 3 pounds lighter than the Yamaha YZ250. The TM is 10 pounds heavier because it has electric start. Remember, the KTM doesn’t have the button. That’s reserved for the off-road models of the bike. It sells for quite a bit less than the off-road E-start TPI bikes, but it’s still not cheap. The KTM is $8299. The Husky is $8399. The Yamaha is $7499 and the TM is $9195.
The KTM is a fun bike to ride, but a demanding bike to race. It’s so fast and light that you have to be on top of your game. If the track is smooth, fast and well prepped, nothing is more fun than the 250SX. It’s so crisp and responsive, you can’t help but laugh to yourself while you ride it. If, on the other hand, conditions are crummy, you have to relearn the art of throttle control. You can’t just wack open the throttle and expect to hook up. For many riders, managing the hit is especially difficult on jumps. When you get a little tired, it’s hard to judge how much gas to give it. As our shootout progresses, we will have more on how these four bikes compare, and the full story will be in the August 2020 print edition of Dirt Bike.
That’s all for this week. Take care and stay safe!