In this weeks Two Stroke Tuesday brought to you by RYDCREW.com we give you a sneak peek at an upcoming YZ250X project, show you how to ride a two stroke like a professional and take you back in time to revisit FRANKENBIKE our CR250 24 hour bike build.
Yamaha did a great job with the YZ250X ! BUT we have to try and make it better, after all it is our job. An IMS oversized tank was a must .
Sunstar chain and sprockets with a TM Designs rear chain guide are offroad staples.
The Pro Circuit Platinum 2 pipe is designed to give more grunt off bottom and is made of a thicker material than the stock unit.
The MSR Hard Parts pegs are designed to improve traction and allow easier movement with the raised pattern of the teeth.
It was probably the dumbest idea that ever came out of an editorial meeting. These meetings are already known to generate cases of mass stupidity, as editors, staff members and test riders get together to discuss future issues of Dirt Bike, but this particular idea was special. “Why don’t we get a super-cheap used bike off Craigslist and see how far it goes in the 24 Hours of Glen Helen?” someone said.
“You know what would be good?” chimed in someone else. “If we raced it as-is, no race prep whatsoever.”
“Okay, but what if we had all the parts in the pits, ready to go? When the clutch breaks, we put in a new one. When the tires go flat or when we break spokes, we put on new wheels. You have to do most of that stuff during the 24-Hour anyway.”
The editors were working up a frenzy. “Yeah, that would be great. We could start the race with a used, clapped-out motorcycle and finish with a brand-new one! It would be the opposite of normal.”
Thus it began. Dirt Bike’s entry into the 2014 JBC 24 Hours of Glen Helen would be the most memorable effort in years. The search for the most wretched used bike on Craigslist began.
Saying that you’ll start a major motorcycle race on a wreck of a motorcycle is one thing. Actually doing it is something else. The perfect candidate appeared almost immediately.
HONDA CR250 MOTOCROSS BIKE
–2004 frame with a 2000 engine
–No pink slip
If you remember your Honda two-stroke history, you would probably stop and stare at that ad too. The Honda always had a great motor, but had various other issues through the ’80s and ’90s. It was the first bike with an upside-down fork in ’89 and the first bike with an aluminum frame in ’97, but neither one of those things worked at first. In 2002, the Honda was completely redone. It got a new frame that flexed in all the right spots. It got a new twin-chamber Showa fork, and it got a revolutionary new motor with an electronic power valve. The bike handled great; that frame wasn’t so different from the one that Honda still uses. The fork was a huge leap forward, but the motor was another story. It was a dog. The instant throttle response that Hondas enjoyed for years was gone. The Factory Connection team went so far as to put Mike LaRocco on a hybrid bike with the new frame and the old motor until they could figure out how to get power out of the new one. Eventually, the factory guys got the new motor to work, but those changes never made it into production. The Honda CRF450R that was introduced later in 2002 would herald the end of the CR250R. From that point forward, all Honda’s R&D effort went into the four-stroke.
So, the Craigslist bike was perfect. It was the best motor combined with the best chassis for the CR. We looked at it late at night, ran the VIN (just to be sure it wasn’t really Mike LaRocco’s bike), offered $1200 and brought it home. That turned out to be way more than it was worth.
It wasn’t until the next day that we really understood the gross stupidity of our original idea. Yes, it was a 2000 engine in a 2004 frame, but it wasn’t bolted in. The motor mounts didn’t line up, so they were never installed. The gas tank wasn’t bolted up, either—and wouldn’t. It was from some other bike. The rear wheel was from a Kawasaki. The footpegs were from some other donor and pointed upward at a 45-degree angle. The brakes didn’t work. The grips were destroyed from sitting outside in the sun and were coated in some sticky glue that leaked through the split rubber and never set. The throttle took both hands to turn. It ran, but it was clear that the power valve was stuck. The idea of actually starting a race on this bike was a little terrifying. If someone actually agreed to take it around that first lap of the 24-Hour, he would never come back alive.
Clearly, we didn’t inspect the bike adequately at the point of purchase. In fact, we didn’t inspect it at all. It was what it claimed to be, however, and that was good enough to make it a different kind of project. Was the combination of the 2000 motor and the 2004 frame as good in real life as it seemed on paper? There are actually a number of people who have done the same project, so there’s a fair amount of information to be gleaned from Internet chat rooms. The general consensus is that the conversion is only worthwhile if you are determined to leave the motor stock. If we altered the squish band, decked the cylinder and raised the compression on the new motor, it would actually have been more powerful. But, for the 24-Hour, we didn’t want to raise the compression or do anything that might make the bike less reliable on pump gas.
Making the motor fit wasn’t hard, but we had to be sort of like butchers. The front motor mount is about 3mm off. If you want to cut off the frame tabs and re-weld them, more power to you. We used a Dremel to ovalize the frame holes. The head stays could be modified the same way, but you could also cut new ones and use spacers to deal with the offset between the engine and the frame. There’s actually a guy on eBay who sells them ready to go (search “MXbonz”).
The airbox and radiators from the ’00 CR250R fit perfectly. Luckily, those were already on the Frankenbike. But, the subframe was also from the ’00 Honda, and it didn’t fit at all. We got a new ’04 subframe from AC Racing. It took some fabrication to make the earlier airbox meld with the later subframe and number plates, but it wasn’t bad. The project wasn’t nearly as hard as other frame/engine marriages we’ve performed.
The original plan fell apart because the engine had to be rebuilt before the race. If it had just been worn out, that wouldn’t have presented a problem. You really can do a two-stroke top-end job in an extended pit stop. But, as with so many old bikes, the Frankenbike wasn’t worn out; it was abused. Someone had previously taken the motor apart and had no idea how to put it back together. The power valve was assembled improperly, and the clutch hub bushing was installed upside down. There were numerous missing washers. Thank goodness the previous owner hadn’t gone into the gearbox; it was well-used but unmolested. We decided the gears themselves could go for another round, so we invested $120 in a Hot Rods rod kit. A Hinson clutch was necessary because of the owner-initiated damage to the original hub. To be fair, we probably would have put a Hinson on a brand-new bike too. We found some parts and put it all back together with a Boyesen Rad valve ($160) to replace the frayed stock reeds.
All the stock controls were destroyed, of course—from the curled levers to the shattered throttle housing. Motion Pro has all that stuff, as well as the clutch and throttle cables we needed, all of which were less expensive than the original OE parts. We used IMS’ Pro Series footpegs ($80) to replace the oddly erect pegs that were on the bike. Pro Taper sells the springs and hardware to mount them-—again, cheaper than OE (the original stuff was, naturally, missing).
We used 2004 plastic from Acerbis, which totaled around $130. The 2004 number plates left a large unprotected gap in the side of the ’00 airbox. We patched that with a hodgepodge of plastic from the parts bin. There were, in fact, bunches of small parts that came out of old boxes of stuff in the back of the garage. We knew we kept that stuff for a reason. The fuel tank presented a minor problem. The mystery gas tank was swapped for an IMS 3.1-gallon tank ($275) designed for the ’04 frame, but there was a small clearance problem. The older engine had a slightly different shape. We had to heat the bottom of the new tank and make a small depression to clear the spark plug.
The biggest replacement parts of the whole project actually weren’t that expensive. Rocky Mountain MC sells a replacement set of wheels for under $500. We used Pro Taper sprockets, discs and a chain to finish them up, along with Motion Pro rim locks and Dunlop Tires.
BETTER THAN ORIGINAL
To make the Honda competitive with modern bikes, it needed more than a restoration. The twin-chamber Showa fork had a modern design, but Bob Bell at Precision Concepts has come up with a number of modifications over the last 10 years to get the most out of that fork. Same for the shock. We also installed a Scott’s steering damper with a BRP top clamp. That damper gets moved from bike to bike, so we can’t really add that to the overall price of the bike. The clamp and mounting kits were about $250.
So, instead of starting the race with a rolling roach, we had the cleanest attention magnet of the race. Nothing generates goodwill like an older two-stroke. The combination of the best motor and the best frame in the CR250R’s history was a winner. In the later years of the Honda’s existence, it was pushed to the back burner by Yamaha, KTM and Suzuki, all of which had better 250cc motors. The Honda actually handled better than any of them, though. If Honda had kept the last of the mechanical power-valve Honda motors, it would have stayed closer to the top of the two-stroke field (when you compare stock machines). But, when you measure our Honda against the current 250cc two-strokes from Yamaha and KTM, it comes up a little short. The power is a little softer. The clutch pull is a little harder, and the bike just feels a little older. Handling is another story. Frankenbike is magic. It’s lighter and has better suspension than the new two-strokes. And, it turns! The Honda was always incredible in corners. Back in the day, we used to complain about headshake, but that was completely eliminated by the steering damper.
As for the race, it could have gone better. Frankenbike suffered a race-ending crash early in the 24-Hour, forcing the crew to turn to the back-up bike. But, all of our riders would have preferred the two-stroke. The good news is that the bike is still fresh, ready for its next race. Was it a cost-effective project? The total in parts was around $3000, plus the initial cost of the bike. That’s what it would cost to get virtually any two-stroke restored to new condition. You can do a little better if you buy a less-destroyed core, and a two-stoke project will still cost way less than a brand-new four-stroke. And as with any project, the journey is as much fun as the destination.