Stock Moto has brought many new faces behind the visors this year.  Fresh minds, fresh ideas, a new frame of reference, a new culture to the sport.  Bangin' Gears is a new feature from Kartweb intended to inform new shifter racers of some of the lessons learned as well as help guide this new culture in a positive direction. 

It's no secret that karting has become more fragmented over the last few years, in fact it's always been somewhat fragmented.  2006 presents an opportunity for unification.  No, not everyone will be made happy, it's more a matter of introducing compromise based on properly informed decisions. 

The March issue of Bangin' Gears focuses on the facts about Stock Moto power.  American Motorsport is obsessed with the concept that power is everything;  Maybe thats true in drag racing, but it's not true in shifter kart racing.  Power is indeed a factor but it's over hyped by competitor and retailers alike.

Lets take a look at a summary of the big picture;

Ask any of the top Moto builders today what the differences are between a SuperPro Spec CR125 and a Stock Moto configuration.  The answer is 5-6 HP, and a wider powerband.  Then ask how typically how much power drops off from being 1, 2, and 3 jet sizes too fat? 

First where do those 5-6 extra ponies come from?

• Compression - 2.0 + HP.
• Porting - 2.0+ HP
• RS or V-Force Reedcage - 1.0 HP
• ABEC 3 Min Bearings - negligible gain, .1HP @ 12,000 RPM theoretical.

Thats 5HP so far, what about that last HP?  In most cases from port work that goes beyond a reasonable level of risk for the majority of karters to run.  There gets to be a point where exhaust port size gets so wide the risk of hanging a ring or destroying a piston with rapid bridge-wear & scuffing requires changing - and fitting a piston about every 20 minutes of operation.  The same is true for running compression on the fine edge of detonation.  The air may change just a little bit which is enough to create catastrophic levels of detonation, so most builders leave that last HP out for reliability sake.  They may save it for a single annual event where they will be right alongside the racer to tune for them.

With the above 3 modifications other things are also are optimized for fractional and systemic value.  Systemic is the key word since without the first 3 mods, the systemic mods won't provide any positive gains on a Stock Moto.  Systemic mods are;

• RS125 Piston
• RS125 Carb Boot
• Removal of Kick Start boss (Legacy)
• Reed Plenum shaping (Legacy)
• Matching Crankcase junction to ported Cylinder (Legacy)

The effect each of these things contributes to the changes made rather then being a benefit on it's own with a Stock Moto configuration.  The RS piston isn't allowed so we'll skip over that.

RS125 Carb Boot comes in a 5° vertical or 5° horizontal bend.  They actually measure about 12° but 5° is how they are commonly referred to.  The CR125 boot has a 30° bend.  A simplistic conclusion would be that the 30° is more restrictive and therefore the RS125 would be an advantage.  It doesn't work that way any more then say cutting off the rear cone of the pipe would be better (neglecting the noise).  The boot is much more then just a mount for the carburetor, it controls the flow into the reeds.  This is covered in the Stock Moto FAQ page at some detail. Coupled with the Stock Reed Cage the RS125 Boot with stuffers cut off will only reduce power to less then the CR125 Boot will produce.  There is no difference in power between the 5° Horizontal RS 125 Boot and the 5° Vertical RS125 Boot.  The Horizontal boot doesn't require cutting the Kick Start Boss where the Vertical Boot does.

Does that seem complicated to understand?  Probably not, but what adds to the disruption and fragmentation is the the intended mis-representation of facts.

Reed Plenum shaping does affect the powerband more then anything else.  In simple terms, it takes from the bottom end, below about 10,500 and gives back to the top end.  For a Stock Moto thats limited in the peak RPM efficiency by the ignition curve the net result is actually a loss on the track.  If the motor were able to run in the 12,800 zone, it would help but only a small amount.

Matching Crankcase junction to ported Cylinder becomes a hindrance to power on a Stock Cylinder.  The ground area introduces the protruding edge of the stock Cylinder at the junction where the Crankcase was ground resulting in a drop of airflow.

The Stock Moto Standards eliminate all the modifications that enhance Horsepower from creative effort.  But what about powerband and drivability?

Programmable Ignitions are all about shaping the powerband without any real affect on peak power. They are not allowed on a Stock Moto.  Likewise some port timing stagger can widen the powerband, again not allowed.  In the end, powerband enhancements are limited by the carburetor, pipe and silencer which tend to be the most controversial subjects.

Pipe/Silencer has the most profound effect on a motor. As the Stock Moto Standards have specified the RCE T3, RLV R4, and RLV6800 the reviews on these are on the Stock Moto FAQ page .

Carburetors remain an elusive concern.  Mostly it's fear of the unknown that seems to be at the center of it all.  The purpose of the carb is simple; allow as much air through the bore as possible while keeping a fixed ratio of mixture no matter what the throttle position is.  Looking back at the Pro Moto years the following carbs have all been proven winners;  Mikuni TMX, Keihn PWK, Dell'Orto VHSB, Kiehn PWM.  Depending who builds the motor is a matter of who prefers a specific carburetor.  Why?  Thats what they know how to tune the best.  So is there an advantage to one carb over another?  Absolutely.  The best carb is the one you're familiar with tuning.

Take any one of the carbs above you think is the worst and have it properly tuned.  Then take any other carb from above and go 1 full jet size fatter.  Which do you really think will be faster?

The biggest challenge to Stock Moto today isn't in the tiny differences in power of the motors that may exist, it's the in the self interest of the people who create confusion in the program.  With the release of the Stock Moto Standards Unification Program came a hailstorm of mis-information from a few of the folks in the sport who obviously want to keep karting locked up in some kind of secret society and fragmented.  Karting has been there and done that for too many years.  It's not the power of the motor that really at question;  Its the power of a few individuals who don't even race thats at question.

2006 offers a bold new approach to the issues through unification.  Unification takes compromise, cooperation and commitment to what the majority can accomplish together.  It takes a personal responsibility and just a dab of common sense to see through the myths perpetuated by a few to get the most enjoyment from this sport that tends to consume us.