Wardy,
My KTM was a 625cc Adventure, the good part is it only weighed 400 lbs and held 7 gallons of gas, just in case you want to ride for the whole summer!
Now I have a YZ155 and I love drag racing 250Fs.
The AMA is freaking out because less people are racing but more are practising. Us practioners don't worry about rules, points, shiny disco jackets, just ride time.
I'm working on some possible ideas for a Pit Pass Radio show, here is a preview of my notes.
Proposed topics for discussion are included in this article
AMA Rule Changes – Rich Man Poor Man Sequel Gets Political!
Super Stock Class Rule Changes
In an effort to reduce the number of protests at major amateur races and allow a measure of customization to improve safety, the AMA allowed changes like suspension revalving and springs to original components, and aftermarket controls like handlebars, grips, and levers. In previous years riders have been protested and disqualified for silly things like aftermarket handgrips that don’t offer a competitive advantage.
The biggest hassles happened at AMA Youth Qualifiers for Stock classes, where parents have a significant investment in attending an event and their kid misses qualifying by a few places so the parents protest the riders ahead of them in order to bump anybody for the most insignificant differences from stock. These protests added extra time to events and discouraged race promoters from applying for Youth events.
Drawing a Line in the Dirt - 4-Stroke 150s not allowed in the 85cc class
The FIM passed rules regarding the integration of the latest models of 4-stroke 150cc bikes into the 85cc minicycle classes. This move will surely push out the stead fast 2-stroke bikes from Europe.
The AMA didn’t concur with the FIM and that is controversial since they have followed the FIM rule changes in the past. AMA Congressmen, mostly a collection of race promoters, club officials, and track owners held solidarity on the integration of 4-strokes into the mini class despite intense lobbying by the manufacturers. Congressmen “drew a line in the dirt” allowing only the big wheel CRF150 and YZ150F in the Supermini and Junior classes. The main point sited is this; 4-strokes are raising the cost of racing and less fortunate people are getting discouraged and pushed out of racing because they can’t afford to compete.
250Fs – Class Bully Gets Shoved Around!
The most dramatic rule proposal was to push the 250 4-strokes into the 250 class to compete against 2-strokes. The rule didn’t pass, probably because it presented a logistical problem for promoters and the backlash from dealers and manufacturers would’ve been huge.
Consider this, if the rule went through promoters would have far more entrants in the 250 class and far fewer in the 125 class. That means that they would have to run more 250 qualifiers, semis, and finals. It would’ve changed the format of local racing. The motorcycle manufacturers and dealers were concerned that there wouldn’t be enough 2-stroke 250 bikes available, since those bikes would have the class advantage. Manufacturers produce next years’ models in March and dealers place orders in July. The other concern was that the market price of 250Fs both new and used would fall creating rapid deflation in the market. Dealers faced the possibility of being stuck with a lot of money worth of 250F inventory that was not competitive.
The obvious solution is to create a 250F class and let the rich kids and their parent fight it out together, but don’t look for that rule proposal anytime soon. Savvy race promoters like Aaron Vincer of Motosports Park in Byron Illinois have created 125cc 2-stroke only classes. Aaron recognized that with a large supply of cheap, used, non-current 125s on the market, creating a new class might give new riders the incentive to spend more money on racing rather than on just practicing.
Solution to the 125 Class
Here’s an idea for the AMA, why not separate 250Fs from the 125 class by starting an Amateur Lite class. Leave the 125s compete with 150Fs and 105s and encourage younger less experienced growing riders to populate the class until it can eventually be phased out as the manufacturers stop making new model 125s. The riders who seem to suffer the biggest engine catastrophies with 250Fs are inexperienced riders who jump from a 85 2-stroke to a 250F. The 125 class at the nationals should be for Juniors/Schoolboy.
Amateur Lite could be an A class at the amateur nationals and act as a lead-in for racers to step up to the Arenacross series. The long term goal of the AMA is to provide a “Goal Path” for professional racers by making them race Arenacross before being eligible to race Supercross. Why not extend the “farm system” to amateur racing with a premier A class named Amateur Lites?
Opening Up the Open Class
When motocross came to America in 1966, the 500s were the premier class in the world championships. 5-Time World Champion Roger DeCoster was once quoted as saying “anything less than an open bike, is just a baby bike”. The AMA has had a tenuous relationship with the Open class, discontinuing it from pro racing in the mid-1990s and constantly changing the rules for amateur racing with complicated restrictions regarding 2&4-stroke displacement. With current rules, in order to race a 250 2-stroke in the Open class, it has to be 15% larger in displacement (285cc) which means spending as much as $2,500 with aftermarket hop-up shops. That’s cost prohibitive for most riders, and most of the late model 250T engines are designed to be dimensionally impossible to enlarge the displacement beyond 265cc.
The AMA should make the Open class 251cc and greater which enables greater participation and competition. 450Fs should be in the Open class because they will always be far more competitive than a standard 250T. Consider this, inexpensive hop-ups can be performed to 250Ts to bump displacement to 265cc, 250Fs can be modified for even less money to 262cc. A wide variety of 500cc 2-strokes, and anything 4-stroke ranging from all the way up to 650cc 4-strokes should be legal for the Open class just like Europe.
AMA Pro Conundrum
Concerns of rising injury rates (specifically Marshall and Fonseca) and the steady upward development of 450s towards the 70hp mark, the AMA proposed some thought provoking ideas for the future of the Arenacross and Supercross 450 class, tame down the engines in displacement and horsepower. This presents the manufacturers with some hard R&D decisions. Do they make a detuned 450 or a hopped-up 250? What do they use as a platform? A 300cc engine kit could be easily produced with these components; crankshaft, cylinder, piston, cylinder head, exhaust pipe, and ignition. These kits could be produced and marketed by the manufacturers for retrofit on 250F models.
Heres another idea, why not keep 450s, shift technology thinking from tuning to detuning and narrow the focus the sound issue. Making 450s quieter will automatically detune the power. Its like killing 2 birds with one stone. Imagine this, dual mufflers with u-tubes pointing to the ground could be fashioned and the side panel space increased to cover the system and provide greater advertising space.
Deregulation Enables Aftermarket Explosion!
The AMA rule changes included a certain measure of deregulation that could enable growth of the aftermarket and more mass customization for consumers. In the stock classes, suspension component customization and control options will surely proliferate. In the Supermini class, the ban on crankshaft stroking has been rescinded and the class limit has been changed from 105 to 112 in order to achieve parity with the NMA. The 125 class is wide open, with CRF150s, Superminins, and a maximum of 144cc 125s in competition together. Look for products like big bore pistons, stroker cranks, as well as a bevy of engine components designed for greater displacement engines like cylinder kits, camshafts, bigger valves, exhaust systems, and ignitions.
Tackling the Problem
The biggest controversy facing American motocross is the question of parity in displacement between 2 & 4-stroke engines, and is the driving force for most of the proposed 2007 rule changes. The average operating cost per engine hour is as much as three times greater on a 4-stroke. And although the powerbands of 4-strokes are very forgiving and enhance rider abilities, the consequences of rider error are not forgiving. One extra downshift in the air over a jump can cause mechanical overrevving and energetic engine disassembly (blow-up). In an instant a rider can be faced with a $2,500 repair bill, and risk pushing him out of the sport entirely.
The power advantage and cost disadvantage of 4-strokes have created class and displacement disparity. In America, motocross has traditionally been a low cost motorsport where rider skill is paramount. In Europe the opposite is true, there are no poor people racing motocross so great effort is expended on making the motorcycle a bigger part of the winning equation. Europeans spend more Euros per capita on performance enhancements to their bikes than Americans. Integrating 4-strokes into the minicycle classes is a natural evolution but it presents a variety of future problems for the next generation of European riders. Riding 2-stroke dirt bikes encourages a rider to develop skills in managing forward motion through keen skills in clutching, shifting, throttle control, braking, and controlling the gyroscopic energy of a motorcycle during jumping. The pitch, roll, and yaw of a motorcycle can be affected by torque reactions in the three gyroscopes (the wheels and the crankshaft). Initiating torque reactions on a 2-stroke bike are much more difficult than on a 4-stroke dirt bike. For example, changing the pitch of a 2-stroke bike to lower the front end for a smooth landing from a table-top jump involves pulling in the clutch, chopping the throttle, and stabbing the rear brake in order to initiate a torque reaction of the rear wheel. On a 4-stroke bike, a rider can easily affect a change in pitch just by backing off the throttle.
Originally the Japanese manufacturers lobbied the AMA to allow 250 4-strokes to compete against 125cc 2-strokes and 450Fs to compete against 250Ts. The AMA allowed the rule to pass without ever seeing a production 4-stroke, and they made special considerations regarding non-homogulated prototype 4-strokes to race in professional events (Doug Henry 1997 Yamaha YZ400F).
In recent years, Cobra Motorcycle president Sean Hilbert, and chief technical officer Phil McDowell have attempted to lobby the AMA with a revised concept of determining parity in displacement between 2 & 4-strokes. Previously formulas like peak horsepower, area under the curve of a dyno chart, and thermal units have all been discussed but there is a new twist on the horizon to this old controversy. Consider that modern 4-stroke dirt bikes evolved from F-1 racecars but there are still major advancements that could be implemented to create a greater difference in power between 2&4-strokes. Two-stroke engines are limited in RPM by port-time-area, exhaust pipe dimensions, and the efficiency of cylinder scavenging. Four-stroke engines are limited mostly by valve trains (spring reaction and valve float). By implementing F-1 technology like ignition systems with no rev limiter, lighter reciprocating components, and pneumatic valve trains that can push the rev limit of a 450 to 19,000 rpm and produce as much as 85hp. That is nearly double the average power of a modern 250 2-stroke.
More technology is starting to trickle down from F-1. Pneumatic valve train assemblies from F-1 engines are about the same size as the ones used on 450 dirt bikes. These parts consist of two bucket shaped parts, one acts as the tappet riding against the cam and actuating the valve and the other is the gas spring and includes a seal and a jet orifice and check valve linked to a source of pressurized nitrogen gas tank. Gas springs offer faster reaction time than coil springs. Tuners in the UK have already successfully adapted gas springs into YZF450 engines. Factory teams are using lightweight valve train parts and coil springs with a range up to 14,000 rpm. Programmable ignitions from Vortex, enable tuners to eliminate the rev limiter option and let the rider decide how high to rev the engine. The current crop of factory 450cc bikes produce and estimated 20hp more than a production 450. (68 vs. 48hp)
