200 MPH Or Bust!

Gearing
Most people think that a bike should be geared to reach the speed desired at redline, but that is not always true. On some bikes peak power is not at the redline. When shooting for a given speed at different top speed courses like Maxton or Texas, the riders use speed calculators (spreadsheets developed for each bike), then pick the gearing to hit that speed at a given rpm. On 1000s and bigger bikes it usually is near redline as it is for nitrous and turbos, but on 600s and 750s peak power is far short of the rev limiter.

A critical part of the 200 mph equation is getting the proper gearing. If a bike is geared "too low" the engine will hit the rev limiter before ever reaching the target speed. On the other hand, if it is geared "too tall" then it may not have enough power to pull all the way to peak power in top gear. In order for a bike to achieve its true top speed the gearing must be such that the combination of aerodynamic and mechanical drag forces are exactly equal to the bike's power at the rear wheel as seen on a dyno.

With stock gearing our 'Busa was into the redline but falling shy of the rev limiter during extended nitrous sprays, indicating that we had the correct gearing, but there was simply too much wind resistance and not enough power to push us that extra 500 rpm. Lower gearing would've pushed it into the limiter, but reduced the top speed.

Breaking Wind
There have been only a few bikes at Maxton (in ideal conditions) to go 200 mph with less than 200 hp. We wondered if there was any scientific proof to back up the legend that it takes at least 200 hp to go 200 mph, so we turned to Gary Eaker at A2 Wind Tunnel in Mooresville, North Carolina.

With an '06 Hayabusa in the wind tunnel we were able to tell the precise aerodynamic load. Then, using estimates of rolling resistance, we determined the horsepower required to reach 200 mph. Data on the 2006 Hayabusa showed that it had a corrected Coefficient of Drag of .468 and CD*A (coefficient of drag multiplied by frontal area) of 3.15. Using that as the basis, Eaker concluded that the 'Busa needs 196.3 hp to reach 200 mph assuming unlimited distance for acceleration. For comparisons, a ZX-14 requires 202.4 hp to reach the same 200 mph, indicating a less efficient aerodynamic design.

This calculation was made with a six foot, 180 pound rider however, and therefore doesn't apply to our conditions with some sixty more pounds on board. The aerodynamic numbers in the tunnel don't take into account anything but wind resistance.They don't factor in weight and since physical size dictated wind resistance in this case, weight was our biggest hindrance.

Scott Guthrie:
Scott is one of seven people in the world that has been over 250 mph on a Hayabusa and has been land speed racing motorcycles for 35 years.

"Everybody who rides a Hayabusa secretly believes they can go 200 mph. Then they find out how hard it is to actually do it."

RC51 Farce
Honda RC51 rider Sam Tilley was nailed with a 205 mph speeding ticket that was issued from a police airplane. Tilley went so far as to have the bike dyno tested for top speed prior to his court date, and the result showed it topping out at 160 mph. The Minnesota State Police have held firm though, and to this day claim the 205 mph reading was accurate.

Lee Shierts:
Back in 1999 it was Lee Shierts that laid down the first official 200 mph pass on the 'Busa at Maxton, North Carolina. Lee currently holds the Maxton track record at the event at 260 mph. Lee talked to us about the 1999 bike and the Rich Yancy 260 mph machine: "The 1999 bike was making about 188 hp at the rear tire with internal engine mods-that bike went exactly 200.00 mph.

The 260 mph 'Busa wasn't a super high tech bike. It was rather a highly refined package. It used a Power Commander II and didn't have a multistage boost controller other than my butt and throttle hand. We ran the bike at about 24psi and it made about 500 hp at that boost."