So You Want to Be a Flat-Track Racer?

AMA Pro Singles Build, Part One

By Dan Jacobson Sr.
Photos by Tim McBride and Tim Handrich
FARGO, ND, DEC. 1, 2011

In all my 40 years of flat-track racing, never before has it been easier to build a pro flat-track bike. Buy a motocross bike, put a 19-inch front wheel and tires on it, and go race…

Yes, that works, but to go fast like the AMA Pro Singles and Grand National Singles Experts, I have a few tips for your rebuild. If you have ever thought about building a racer, this AMA Pro Singles-legal bike will give you a platform with plenty to handle for any rider. The flat-track world is an exclusive but friendly group or family of racers, with a rebounding fan base. If there was ever a time to join the family, this is “the road to travel” to get there.

MX rides are made to run 40 to 60 mph, not 130 mph. The stress on the half mile or mile tracks is far different, as the throttle is truly wide open for extended periods. M3 Racing’s Mark McGrew has carefully studied the fastest rides and what the teams have done to make them fast and last, creating a blueprint to follow on your build. Just like any racing creation, there is only one way to do it right, and this is what we have done, so you can get it right the first time.

To build these AMA Pro Racing-legal, we start with the engine. For this project, we are using a 2007 Honda CRF450; the same formula works with other similar brands.

We first went to Hot Rods for a sturdy crankshaft and rod, cylinder and cam. You just don’t know the value of the Hot Rods products until you try running the full season on stock parts and your engine becomes scrap metal when a broken rod slices through the cases like a food processor. Hot Rods’ dealership network has the complete package ready to go.

After installing the Hot Rods crank and rod package, we want to make sure the all-important start will be flawless. For the clutch basket, plates, springs and hub, we went to a longtime favorite, Barnett Tool & Engineering, provider of USA-made product since 1948. For this project, we added the clutch cover with the stylish Barnett logo. Since the motor is already out, don’t forget to set up the drain plugs for safety wire and plan for a radiator overflow catch bottle; it’s never fun to wait in tech just to be sent back to do it in the pits.

The ported and flowed head is where most of the horsepower is made. A 13:1 compression-ratio CP piston from Fist City MX finishes the horsepower needed in the combustion chamber. Being restricted to OEM-size valves and locations is a money-saving rule from AMA Pro Racing (and we will see more of this as we go on). At 13,500 rpm, valves and pistons don’t want to get too friendly. Valves and springs from your Kibblewhite Precision Machining dealer are your best bet. Matching the top end with the right Kibblewhite valves and springs allows the stage-three Hot Cam and CP piston to do their work and develop power right up to the rev-limiter.

For the big tracks, we called on D&D Performance Exhaust to finish the flow with their famous down pipe. Using this pipe will add horsepower and allow the engine to be away from heat buildup seen with the up pipe. Looking through the photos of AMA Pro Singles and Expert Singles winners, one notices that most have D&D pipes. D&D has performance pipes for street and off-road rides. Since we have dealt with outflow, let’s cover the inflow, since carb jetting will need changing to balance the new high-performance parts.

Tuning the carb will change with elevation even after you find the starting baseline. We went from a 178 to a 205 main jet due to the increased flow from the head and the D&D exhaust pipe. We did some wide-open runs and then killed the engine to do a reliable plug check.

K&N Filters has been my favorite company since the company started when it comes to making sure the dirt stays on the track and not in our new high-performance engine! For this build, we stayed with the OEM filter box and opened up more airflow, since we do not need to worry about going through mudholes at 100 mph, thanks to AMA Pro Racing director of competition Steve Morehead. K&N has OEM replacement filters for both engine oil and air – and all the products to keep them serviced. “K&N has been involved with AMA Pro Flat Track Racing since the beginning, when Ken Johnson [the “K” in K&N] and Norm McDonald [the “N” in K&N] developed product in 1969,” says K&N powersports manager Johnny Jump. The complete product line at K&N includes all the vehicles for the team.

For all the OEM parts for our project Honda, we have found Motoworld to have great pricing and quick turnaround on shipping, even to the M3 Racing factory in Hawley, Minnesota. It seems when it comes to just about anything we have needed for racing gear or parts, Motoworld has it covered.

Now that we have a have a race-ready engine, next comes the chassis. Shocks and forks need to perform very differently from their original design. Triples don’t exist in flat-track racing, so the damping and rebounds, ride height, sag, and swingarm angle need to be addressed for traction and control through the turns. With everyone’s engines being very close in horsepower, the big deciders are the chassis and the gearing setup.

My suspension expert, longtime friend and fellow competitor Davey Durelle of Durelle Racing recounts: “I started working on suspension because while I was racing the Grand National Series, I was unable to find anyone who could work on my suspension and actually do what needed to be done. Time after time the suspension companies claimed to have made changes but had no documentation as to what they did or how it affected the damping characteristics of the suspension components, and I certainly never felt any difference. So I built a shock and fork dyno to measure the changes and find the effects of all the different parts. Once I was able to make my bike work where others couldn’t, I was approached by other competitors and race teams, asking me if could fix their suspensions. Within a few years, I had a lot of work to do and less time to go racing.”

With a quick turnaround, our shock and forks were back from Durelle Racing, ready to install.

Having all-new Pivot Works bearings and bushings will give you a solid starting point. When they don’t work right, changing suspension settings will not help, leaving you wondering what’s wrong. Pivot Works has the packaged kits for all your bearing and pivot locations.

Now we have the chassis ready for wheels. With help from Buchanan Spokes, we selected the 19-inch-by-2.15-inch rim for the OEM Honda hub, with disc brakes for the TT events. For the rear end, the OEM hub will get a 19-nich-by-2.5-inch rim. Buchanan’s kit worked great: We laced and trued it up ourselves, but your local motorcycle shop can help.

Buchanan’s rim-and-spoke kit setup goes for about $260 for each end (front and rear), and lacing up to the stock hubs is one way to go. Durelle Racing and Cheney Engineering have quality quick-change rear-wheel assemblies priced around $850 and $600, respectively. There are many advantages to having a quick-change rear wheel: You can flip the tire without removing the tire; and all quick-change wheels fit the same sprockets and disc brake, meaning that gearing changes take only a few minutes.

Handlebars, grips, rubber-covered footpegs, rear-brake lever and line, throttle, clutch lever and seat are all pretty much about the rider’s preference, but here are our suggestions: Vortex V3 MX handlebars; Torc 1 grips (we liked the Holeshot MX1/2 waffled medium compound for grip and comfort); Honda has the answer to the rubber-footpegs rule – On the left side, we moved it up so it doesn’t work like a plow if the rider starts to lay it over too far; Durelle Racing also has a retro “Bates-style” rubber peg to fit stock mounts; we went with the Motion Pro Revolver throttle kit – this is the answer for a durable adjustable throttle; Motion Pro has come up with a changeable cam to give three different throttle responses – slow, medium, fast – providing more control on the short, technical tracks and a quick response on the big tracks.

A seat designed to last and give the rider comfort has its place in building a winning ride. Saddlemen has the answer, with seat pads that can lower your center of gravity, along with the best covers in the business. Fitting your rider’s seat to have the ability to move fore and aft is a must. Saddlemen’s seats, luggage and accessories have the right quality, whether it’s to weather the tough use of flat-track racing or just for daily riding.

To dial in your new racer – finding the right ratio for the track so you can run one gear after the start without hitting the rev-limiter – gearing will be very important. Vortex has OEM sprockets front and rear, and also quick-change sprockets.

Before you go test your new DTX, do yourself a favor and get a Lightshoe hot shoe. Having a shoe that is light and strong, with the right shape and hard surfacing, will make racing safer by helping your knee and ankle stay where you put them. Lightshoe designer and builder Gary Kinzler custom-fits each Lightshoe to the rider’s boot for a reliable fit and directional control.

For the class of the all-important graphics business, it was a no-brainer: Pro Plates managed to fit all our sponsors’ logos and the necessary AMA Pro Racing information with a product that fits and installs nicely with the help of a hair dryer or heat gun. If you don’t feel a professional appearance is important, red electrical tape might almost get you through tech inspection. Pro Plates owner Tim Handrich is a great person to help put your build into winners’-circle shape.

As we move through these Build stories, we will be covering everything you’ll need to know about AMA Pro Flat Track Racing (the best racing on the planet). AMA Pro Racing’s website can also keep you up-to-date on the latest race information. Go to www.amaproracing.com/ft/

Mark McGrew at M3 Racing has the background and knowledge to answer all your questions. Feel free to contact him on FaceBook or by e-mail or phone (see below).

Manufacturers and Parts

Kibblewhite Precision Machine Inc. (KPMI)
(www.kpmivalvetrain.com/)
High-performance valve-spring kit, complete with base washers, valve-guide seals, standard-size titanium intake and exhaust valves, valve guides, titanium spring retainers and HD springs.

Mike Perry (KPMI)
(www.kpmivalvetrain.com/)
Full-on competition multi-angle valve job done on Serdi Valve machine after installing new valve guides and precision honing on Sunnen Valve Guide Machine.

Fist City MX (David)
(fistcitymx.com/)
13:1 CP pistons, Carrillo rod kit with Pro MX (SX) longer rod for heavy dirt-track crank.

Hot Rods, Hot Crank, Hot Cams, Cylinder Works
(www.hotrodsproducts.com/)
HD crank, HD Main bearings, Stage Two cam, new cylinder and top-end gasket sets.

D&D Exhaust
(danddexhaust.com/)
Down pipe, extra baffles and technical advice on jetting/setup.

Vortex
(www.vortexracing.com/)
Handlebars.

K&N Filters
(www.knfilters.com/)
Air and oil filters.

Lightshoe
(lightshoe.com/)
Hot shoes.

Saddlemen
(www.saddlemen.com/store/)
Custom low and high seats.

Motion Pro
(www.motionpro.com/motorcycle/)
Cables, spare levers, tools (spoke wrench, flywheel puller), jackets, chairs, adjustable-ratio throttles.

Pro Plates
(pro-plates.com)
#44 Number/graphics package, #10L side plates and front number plate.

Durelle Racing
(www.durelleracing.com/store/)
Front/rear suspension setup, rear quick-change wheel, sprockets, dirt-track pegs.

Motoworldracing.com
(motoworldracing.com/)
OEM parts, accessories, riding gear (deep discounts), canopies

M3 Racing
Mark McGrew
(www.m3racing.com/ and also on FaceBook.)

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