#HONDA MOTORCYCLE 1990 PRO#

The new HPP motor turned out to be a huge success on the 1990 CR125R. Top-end power remained the motorвЂ™s strong suit, but now riders of lesser skill at least had a shot at keeping it on the pipe. The new HPP motor on the вЂ™90 CR125R offered a stronger midrange and better low-end response than вЂ™89. The valves and their associated springs, cams and pullies were quick to need servicing and tricky to adjust correctly. In use on the CR250R since 1986, the HPP was revered for its performance but reviled for its complexity. As the RPMs climbed, a centrifugal-ball governor engaged and slid the valves open for optimal flow.

At low rpm, the valves were closed to provide the most efficiency. These guillotine valves varied the height of the exhaust port based on engine RPM.

The heart of the HPP system was a set of sliding valves placed at the top of the exhaust port. In addition to their abysmal performance, they also suffered from severe particulate contamination that demanded constant cleaning and disassembly. The phrase вЂњmid-stroke harshnessвЂќ entered the lexicon because of these jackhammers. As delivered, they were badly under-sprung with incredibly harsh damping. These first generation Showa USD forks were just a mess. MXA compared these forks to a Roman catapult and they were not far off. If not for the gruesome forks, it would have been the perfect 125. It was an excellent machine that felt like a rocket after getting off my rather slow вЂ™89 YZ125. I pulled a lot of holeshots on my #291 1990 Honda CR125R in the early nineties. In reality, the ATAC was never as good as more advanced systems like KawasakiвЂ™s KIPS (Kawasaki Integrated Powervalve System) at producing a broad power curve. In theory, the system was like having a вЂњtorqueвЂќ pipe and a вЂњrevвЂњ pipe all in one. When RPMвЂ™s climbed past a pre-determined amount a butterfly valve would close, culling off the ATAC chamber and allowing exhaust gas to flow straight to the pipe. The ATAC system (short for Automatic Torque Amplification Chamber) used a small subchamber at the front of the exhaust port to increase head pipe volume at low RPMвЂ™s. Prior to the HPPвЂ™s inclusion in 1990, the CR125R had relied on the simpler, but less effective ATAC system. The 1990 CR125R was the first Honda 125 to feature a variable exhaust port for the motor. It was a complex and time-consuming system to work on, but it provided HondaвЂ™s two-strokes of the era with exceptional performance. As the RPMвЂ™s climbed, the centrifugal governor would be activated to slide the valves out of the way for better exhaust flow. At low RPM the valves would be closed, effectively lowering the exhaust port height for better low-end torque.

The Honda Power Port system used a set of sliding guillotine valves, powered by a centrifugally activated ball governor, to alter port timing based on engine RPM. For 1990, Honda looked to remedy this one shortcoming by bringing the CR250RвЂ™s Honda Power Port (HPP) system to the CR125R. There was virtually no bottom end and very little midrange for the rider to fall back on. Its pro-oriented motor made major power, but only at the upper end of the RPM range. In 1989, HondaвЂ™s CR125R had been wicked fast but demanding to ride. The addition of the HPP to the 125 gave the little Honda a power advantage that it would not relinquish until the introduction of YamahaвЂ™s game-changing YZ125 in 1996.Photo Credit: Stephan LeGrand The HPP had been used on the CR250 for several years to provide an extremely broad, easy to use powerband. After several years of dominance, the all-new 1990 Honda CR125R had big shoes to fill.ДЎ990 was the first year that the CR125 received HondaвЂ™s complex, but extremely effective Honda Power Port system (HPP). Bikes like the вЂ™87 CR125R were so good in fact, that many people still consider it one of HondaвЂ™s greatest bikes ever. Some years, the other brands were able to top the CR in one category or another, but most of the time it was hard to beat the little Honda as the total package. They had enjoyed a virtual stranglehold on the division since 1986. In 1990, Honda was on quite a roll in the 125 class. When you combined that with its unparalleled reputation for durability, it was hard to beat. Stock it pumped out more power than most of the competitionвЂ™s modified bikes.

#HONDA MOTORCYCLE 1990 PRO#

The вЂ™90 CR125R was a fantastic pro level bike. For this edition of Classic Steel, we are going to take a look back at one of my all-time favorite motorcycles, the 1990 Honda CR125R.

Honda motorcycle 1990