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Tuesday, November 22, 2011

2012 AMA ATV Motocross Championship Schedule Announced

Yamaha's Dustin Nelson Wins WORCS Final Round at Speed World

Cypress, CA (11/14/2011) -Yamaha’s Dustin Nelson closed out the ATV pro racing calendar with an impressive win in the grueling WORCS finale at Speedworld Motocross Park in Surprise, Ariz. on Sunday, Nov. 13. Aboard his YFZ450R, Nelson led nearly the entire 10-lap, 1 ½-hour race and took the checkered flag an amazing 25 seconds ahead of rivals Jeremie Warnia and Josh Frederick. After having already clinched the 2011 Yamaha Quad-X ATV motocross title, Nelson’s first WORCS victory of the year puts him fourth in the WORCS Pro ATV championship points.

The long WORCS racecourse featured about 80% desert trails, sand-washes and hard-packed clay, and 20% Speedworld motocross track. Nelson was third fastest in timed qualifying practice on Saturday, giving him a good gate pick for Sunday’s race. But rainfall on Saturday night and race morning added a significant amount of mud to the course, making getting the holeshot critical for visibility during the opening laps. When the gate dropped, Nelson and his YFZ made a perfect launch, grabbing the holeshot and immediately benefiting from a clear track. He took full advantage of the chance, building up a lead of nearly six seconds by the end of the first long 10-minute lap.
Yamaha's Dustin Nelson
Dustin Nelson placed fourth in the WORCS Pro ATV class aboard his Yamaha YFZ450R Sport ATV

Nelson padded this early lead to nearly 14 seconds by the mid-race refueling stop. Quick work by his crew got him back on track just ahead of Warnia, but he soon got hung up on a berm, letting his rival slip by. Fortunately Warnia still had to pit, and Nelson knew it – so he decided to patiently trail his rival until then. The race was all Nelson’s after Warnia pulled in for fuel, and he quickly opened up an insurmountable lead to the checkers. “I am so stoked!” Nelson said afterwards. “The Yamaha has been great all year, and I am glad we were finally able to put a good day together for the win.” Yamaha ATV racing coordinator Donnie Luce added, “Dustin has had a very impressive 2011 season on his GYTR-prepared YFZ450R. Adding a WORCS off-road win is an excellent way to end the season, while also building momentum and confidence for 2012.”
About Yamaha Motor Corp., U.S.A.
Yamaha Motor Corporation, U.S.A., (YMUS), a leader in the motorsports market, makes the toughest, most capable and versatile ATV and Side-by-Side vehicles. The company’s ever-expanding product offerings also include motorcycles, outboard motors, personal watercraft, snowmobiles, boats, outdoor power equipment, race kart engines, accessories, apparel and much more. YMUS products are sold through a nationwide network of dealers in the United States.

Headquartered in Cypress, Calif., since its incorporation in 1976, Yamaha also has facilities in Wisconsin and Georgia, as well as factory operations in Tennessee and Georgia. For more information on Yamaha, visit http://www.yamaha-motor.com/.

Idol Speed New Website & 2012 ATV Sponsorship Announced

Can-Am / Motoworks Jeremie Warnia Wins at WORCS Championship

Holz Racing ATV & UTV Racers Take Podium at Speed World MX

Lynden, WA (11/17/2011) - The ninth and final round of the 2011 World Off-Road Racing Championship Series was held over the weekend at Speed World in Surprise, Arizona. Three separate classes represented Holz Racing on the podium with two first place finishers, two second place and one third place.

RJ Anderson has raced only three times in the Series this year but managed a win in UTV Class 1 on Saturday in his Holz-built Walker Evans Racing RZR XP 900. Everyone looks forward to a great season in 2012 from RJ. Mark Holz drove his Holz Racing/Motoworks/Can-Am Commander to a third place finish in UTV Class 1. Mark finished the year second in Series Points, just 5 points out of first place.
Holz Racing Jeremie Warnia

Jeremie Warnia took his first WORCS ATV Pro championship aboard his Holz Racing Can-Am DS450 ATV


Jeremie Warnia and Josh Frederick topped the Pro ATV field for 2011, placing first and second in Championship Series points for their Holz Racing / Motoworks / Can-Am team. Jeremie and Josh entered the final round tied in Series points. They finished 2-3 on Saturday, Jeremie edging out for the Championship win. Collins Webster scored another first place finish in Pro-Am ATV Class at Speed World, earning first place in Championship Points with a comfortable 22-point margin.
Holz Racing Products congratulates all their racers on a successful and exciting 2011 season!

About Holz Racing
For 12 years, Holz Racing Products has been building the highest quality, best performing suspensions and chassis components available to the snowmobiling world. Proven by numerous titles, at the toughest proving ground in the hillclimbing world, Jackson Hole. That’s it. Nocompromises, no excuses. We’re driven by a passion to make things stronger, lighter, smarter —in turn making you faster.

Our developmentcycle is as straight forward as we are. Designed on a computer, built by hand and tested on the track and in the woods. Only after we’re certain we’ve built the best we can, then we put it in production and put it in stock. And now for the past five seasons, we’ve taken that same process and applied it to our line of ATV & UTV Products. We build complete packages. Shocks from FOX and Walker Evans along with valving matched to perform at the highest level. Long Travel A-Arms, Extended Swingarms, Long Travel Linkages, Steering Stems, and parts that make the ride better. We strive to keep all our parts in stock and ship things as quick as possible to keep you riding, not waiting for the delivery man. Holz Racing Products... Engineered to Win.

Two Stroke Engine Explanation

A two-stroke in its purest form is extremely simple in construction and operation, as it only has three primary moving parts (the piston, connecting rod, and crankshaft). However, the two-stroke cycle can be difficult for some to visualize at first because certain phases of the cycle occur simultaneously, causing it to be hard to tell when one part of the cycle ends and another begins.
Several different varieties of two-strokes have been developed over the years, and each type has its own set of advantages and disadvantages. This discussion has already prompted many of you to find a more interesting web-site, so I won't go into the sordid details of each type. The subject of the animated GIF (and this dissertation) is known as a case-reed type because induction is controlled by a reed valve mounted in the side of the crankcase.
The easiest way to visualize two-stroke operation is to follow the flow of gases through the engine starting at the air inlet. In this case, the cycle would begin at approximately mid-stroke when the piston is rising, and has covered the transfer port openings:

As the piston moves upward, a vacuum is created beneath the piston in the enclosed volume of the crankcase. Air flows through the reed valve and carburetor to fill the vacuum created in the crankcase. For the purposes of discussion, the intake phase is completed when the piston reaches the top of the stroke (in reality, mixture continues to flow into the crankcase even when the piston is on its way back down due to the inertia of the fuel mixture, especially at high RPM):

During the down stroke, the falling piston creates a positive pressure in the crankcase which causes the reed valve to close. The mixture in the crankcase is compressed until the piston uncovers the transfer port openings, at which point the mixture flows up into the cylinder. The engine depicted here is known as a loop-scavenged two-stroke because the incoming mixture describes a circular path as shown in the picture below. What is not readily apparent in the picture is that the primary portion of the mixture is directed toward the cylinder wall opposite the exhaust port (this reduces the amount of mixture that escapes out the open exhaust port, also known as short-circuiting):

Mixture transfer continues until the piston once again rises high enough to shut off the transfer ports (which is where we started this discussion). Let's fast-forward about 25 degrees of crank rotation to the point where the exhaust port is covered by the piston. The trapped mixture is now compressed by the upward moving piston (at the same time that a new charge is being drawn into the crankcase down below):

Somewhat before the piston reaches the top of the stroke (approximately 30 degrees of crank rotation before top-dead-center), the sparkplug ignites the mixture. This event is timed such that the burning mixture reaches peak pressure slightly after top dead center. The expanding mixture drives the piston downward until it begins to uncover the exhaust port. The majority of the pressure in the cylinder is released within a few degrees of crank rotation after the port begins to open:

Residual exhaust gases are pushed out the exhaust port by the new mixture entering the cylinder from the transfer ports.


That completes the chain of events for the basic two-stroke cycle. The discussion is not complete, however, so if you've made it this far and you are getting bored, then go ahead and scroll down the rest of the way - the animation should be done loading.
The animated demonstration has an added device commonly known as an expansion chamber attached to the exhaust port. The expansion chamber (an improperly named device) utilizes sonic energy contained in the initial sharp pulse of exhaust gas exiting the cylinder to supercharge the cylinder with fresh mixture.
Picking up the discussion at the point shown by the exhaust blowdown picture above, an extremely high energy pulse of exhaust gas enters the header pipe when the piston begins to open the exhaust port:

The sonic compression wave resulting from this abrupt release of cylinder pressure travels down the exhaust pipe until it reaches the beginning of the divergent cone, or diffuser, of the expansion chamber. From the perspective of the sound waves reaching this junction, the diffuser appears almost like an open-ended tube in that part of the energy of the pulse is reflected back up the pipe, except with an inverted sign (a rarefaction, or vacuum pulse is returned). The angle of the walls of the cone determine the magnitude of the returned negative pressure, and the length of the cone defines the duration of the returning waves:

The negative pressure assists the mixture coming up through the transfer ports, and actually draws some of the mixture out into the exhaust header. Meanwhile, the original pressure pulse is still making its way down the expansion chamber, although a considerable portion of its energy was given up in creating the negative pressure waves. The convergent section of the chamber appears like a closed-end tube to the pressure pulse, and as such causes another series of waves to be reflected back up the pipe, except these waves are the same sign as the original (a compression, or pressure wave is returned). Notice that this cone has a sharper angle than the diffuser, so that a larger proportion of energy is extracted from the already weak pressure pulse:

This pulse is timed to reach the exhaust port after the transfer ports close, but before the exhaust port closes. The returning compression wave pushes the mixture drawn into the header by the negative pressure wave back into the cylinder, thus supercharging (a bigger charge than normal) the engine. The straight section of pipe between the two cones exists to ensure that the positive waves reaches the exhaust port at the correct time:

Since this device uses sonic energy to achieve supercharging, it is regulated by the speed of sound in the hot exhaust gas, the dimensions of the different sections of the exhaust system, and the port durations of the engine. Because of this, it is only effective for a very narrow RPM range. This explains why two-stroke motorcycles equipped with expansion chambers have such vicious powerbands (especially in the old days before variable exhaust port timing existed). With the design illustrated here (i.e. a single divergent stage and a single convergent stage), the powerband of the engine will be akin to a 'light switch' - once the expansion chamber goes into resonance, there will be a HUGE, almost instantaneous increase in power. The powerband can be softened somewhat by reducing the angles on the cones, but this is simply due to a lower degree of supercharging. In order to get the best of both worlds (a large power increase and a wide powerband), the cones should consist of several sections, with a different angle for each section. Proper design of even a simple expansion chamber is somewhat of a black art, even though formulae exist that will get you in the ballpark (there is quite a bit more to this than simply choosing the appropriate angles and lengths based on sonic velocity - everything about the pipe comes into play, including the headpipe diameter and length, and the tailpipe ('stinger') diameter and length). Design of a multi-stage expansion chamber becomes incredibly difficult - it basically comes down to the old 'cut and try' approach in the end. This of course is not even considering whether or not the exhaust and transfer port timings and outlet areas have been optimized for expansion chamber use.
Anyway, here is the animation you came to see...

Understanding Wheel Offsets

There are 3 common front offsets for your 400ex. They are 2:3, 3:2, and 4:1. What these numbers mean is the measurment of the rims. The first number is the inside measure of the rim in inches and the second number is the out side measure in inches. The rim offset will not affect shock valving. It will not affect shock valving because the pivot points of the a arms are not changed and the leverage ratio stays the same. This means it will not bottom out any easier.
2:3 Offset - This offset is 2 inches inside and 3 inches out side. This will give the 400ex the most width out of the others. It adds stability but causes more push in the turns and much more bump steer plus it will put more stress on parts like tie rods, spindles, hub studs, bearings, ball joints, and puts some on the upper a arm. A basic definition of bump steer is anything that changes the direction of steering of a tire other than from the driver/riders input. This bump steer is caused by the extra leverage the rims have on the handlebars. Also the offsets change the steering axis inclination (SAI). Stock rims are designed to work with the spindles to give the proper SAI to rim relationship so when you change offsets you change the SAI. So i would not reccomend 2:3 offsets.
3:2 Offset - This offset is 3 inches inside and 2 inches out side. This is the most common offset and easiest to find. It adds one inch to a 400ex total. It eliminates almost all the bumpsteer from 2:3's but there is still a little. It is also very close to stock offset where the quad was designed to be. I would recomend this offset.
4:1 Offset - This offset is 4 inches inside and 1 inch out side. This is usually only used on 400ex's with +3 a-arms to stay under 50 inches. This is not that common unless you go with the hyper rims but you can find it if you look. This is also close to stock offset but you will lose an inch when running it. 4:1's corner better and handle all around better then other offsets because it gives the right steering axis inclination (SAI). Stock offset is about 4:1 and the spindles are designed to have the right SAI with that offset. What SAI means is that if you drew a line thru the center of the ball joints while looking at them from the front, it should hit the ground at the same place a line drawn straight down thru the center of the rim does. This is why the spindle is made with the top ball joint closer to the frame than the lower joint. If you change the offset of the wheels these two lines no longer intersect at the ground. The more the difference the more the leverage that the tires have against you (the handlebars) when any size bump is hit. This leads to more bump steer. Changing from a 4:1 to 3:2 rim adds one inch of leverage to the SAI. A 2:3 rim which many people use to widen the front adds two inches of leverage and more bump steer. Also a steering dampner is used to help this bump steer. A steering damper trys to compensate for the bump steer by making the leverage push against it. People with wider offset wheels will notice a bigger improvement from a steering damper but it is still a helpful modification to any quad. So a wider quad does not always handle and perform better then a narrower one. So a 4:1 wheel gets the SAI where it was designed to be with the spindle to give you better contol. This better control can easily overide the advantage of a wider front for cornering so wider is not always better. Hopefully i have helped some others. Thanks!

How to Read Spark Plug Colors

In General: Reading spark plugs can be a valuable tuning aid. By examining the spark plug insulator color, an experienced personal watercraft engine tuner can determine valuable information about the engine's overall operating condition.
Normal: Grey to Light Golden-Brown Color

  • This condition is ideal, the spark plug and engine air/fuel mixture are operating properly.
Dry: Black Soot Buildup
  • Air/fuel mixture is too rich, the carburetor settings are incorrect, or the flame arrestor is dirty or has mounting problems.
  • Spark plug heat range is too cold for the operating conditions.
  • Ignition system problems causing a weak or intermittent spark.
Wet Fouling: Shiny, Wet, Black Appearance
  • Excessive use of the choke (gas fouled)
  • Prolonged low rpm operation (gas or oil fouled)
  • Fuel to oil ratio is too rich (oil fouled)
Excess Deposits: Bumpy, Chalky Buildup
  • Poor fuel quality
  • Oil leakage into combustion chamber
  • Improper oil used for premix/injected
Overheated: White, Blistered, Melted Electrode
  • Lean air/fuel mixture
  • Spark plug heat range is too hot for operating condition of the engine
  • Plug is not properly gapped and/or torqued onto head
  • Overly advanced timing
A detonation problem would show signs, such as silver specs, black specs, or melting or breakage at the firing tip.
NOTE: Signs of fouling or excessive heat must be traced quickly to prevent further deterioration of performance and to prevent possible engine damage.