From a press release issued by Formula USA:
Formula USA “Thunderbike” Class Rule Change
Aurora, IL: Formula USA intends to utilizes a 3.5 horsepower to weight ratio in the “Thunderbike”class starting at Mid-America Motorplex May 23-25. The 2003 Formula USA Rule Book states (pg 39, section 6.14) that a “Proposed horsepower to weight limit of 3.5 pounds per horsepower may take effect by June 1st.” This rule will first be effective at Mid-America Motorplex on May 23-25 for Round 2 of the Formula USA Championship Series event in Glenwood, Iowa. The rule is intended to make the various brands of machinery in the Thunderbike class equally competitive.
The Thunderbike class (formerly known as Heavyweight Sportsman) has proven to be very interesting competition with various brands of motorcycles. In the past it had acted as another class for Buell Lighting Series racers to test and compete in, as well as a competition forum for various other manufacturers such as Suzuki, Ducati, Triumph, Honda, and their various models of single, twin, and triple cylinder machines. The strongest competition for the Buell in Thunderbike has been the Suzuki SV650. With Buell machines producing anywhere between 90hp to 120hp and weighing 390 to 420 pounds versus Suzuki’s SV producing a wide range from 65hp to 100hp weighing in at 300 to 350 pounds, it has provided close competition for both brands.
Defending Formula USA Thunderbike National Champion is Minnesota’s Jeffrey Johnson racing for Hoban Brother’s Buell / Harley-Davidson. Johnson will display the # 1 plate for 2003, as he defends his National Championship at the six remaining rounds of the Formula USA Championship Series. The next round at Mid-America Motorplex in Glenwood, Iowa places Johnson versus the Championship Cup Series Defending National Thunderbike Champion Ed Key on a Suzuki SV650. Defending Buell Lightning Series National Champion Bryan Bemisderfer will also be in contention along with Daytona top finishers Dave Estok, Joe Rozynski, Richie Morris, Tripp Nobles, Greg Avello, Jerry Wood, Dan Bilanski, and Kiyo Watanabe.
Thunderbike Purse
1st $1,000
2nd $500
3rd $275
4th $250
5th $225
6th $200
7th $175
8th $150
9th $125
10th $100
$3,000
Taken from the 2003 Formula USA & Championship Cup Series Guide for Rules and Regulations:
6.14 THUNDERBIKE – Thunderbike machines, except single cylinder machines, are based upon production models, sold by manufacturers and their dealers in North America for street use. Proof of compliance rests with the competitor entering the motorcycle. Single cylinder machines are exempt from production and street use requirements. Single cylinder 2 stroke GP road race machines are not allowed in this class. All machines must have unaltered VIN numbers.
NOTE: Ducati 748 Series machines are excluded from this class. Proposed horsepower to weight limit of 3.5 lbs per horsepower may take effect by June 1st. (Tested weight divided by tested horsepower during post race inspection.) All competitors will be notified a minimum of 30 days before this limit will be imposed.
6.14.1 Production machines not sold by manufacturers and their dealers for street use in North America via normal commercial channels may be approved on an individual basis. FORMULA USA will maintain a list of non-standard approved models and that list will be available at each event from the Race Director/Referee.
6.14.2. All machines must meet the equipment standards of Section 5, as well as the following:
A. Frame, cylinder head(s), and engine cases must be from the same production model motorcycle. Single cylinder motorcycles may use any frame and engine.
B. The frame must be as originally supplied by the manufacturer on the approved model. Strengthening gussets or tubes may be added. Only brackets or tubes not supporting suspension, engine, or drive line components may be removed. Swing arms may be modified or replaced and rear shocks may be replaced or relocated. Single cylinder motorcycles are excluded from this restriction.
C. Reducing engine size of machines from stock displacement to meet Sportsman class displacement limits is not allowed.
D. Fairings that meet the requirements of Section 5 may be used.
E. Liquid cooling is not allowed unless original equipment on the model being used.
F. Original type of induction system must be retained. If a machine originally was sold with fuel injection, then it must remain fuel injected. If the machine originally came with carburetors, then it must use carburetors, however they need not be the original type or size.
6.14.3- Thunderbike Class displacement limits are absolute and are set as follows:
THUNDERBIKE
Single cylinder, Unlimited displacement
Two stroke, Unlimited displacement
Twin cylinder, air cooled, Unlimited displacement
Twin cylinder, liquid cooled, 3 or less valves per cylinder, Unlimited displacement
Twin cylinder, liquid cooled, 4 valve per cylinder, non-desmodromic valves, up to 800cc
Three cylinder, non-fuel injected, up to 1200cc
Four cylinder, air-cooled, up to 1200cc
Four cylinder, liquid cooled, 1990 to 1992 model year, up to 650cc
Four cylinder, liquid cooled (oil or water), pre-1990 model year, up to 860cc
All air-cooled, 2-valve, unlimited displacement
F-USA Adds Power-to-weight Rule To Thunderbike Class
F-USA Adds Power-to-weight Rule To Thunderbike Class
© 2003, Roadracing World Publishing, Inc.
![F-USA Adds Power-to-weight Rule To Thunderbike Class](/wp-content/themes/racing-map/images/No_image_available.png)