Limited Kit and Sleeper Kit

Quoted from Group K's page. Not measured here, and not reproducible without knowing the conditions, which are mostly not published.

Top speed, Sleeper Kit with 40mm carburettors

60 mph at 7,120 RPM Group K's figure for its own package, against a stock baseline they give as 55 mph at 6,780 RPM. The 1997 rev limiter is stated as 7,150 RPM, so the package runs close to it.

Top speed, Sleeper Kit with 38mm carburettors

59 mph at 7,050 RPM Group K's figure. The 38mm set is taken off the 720, which they present as the cheaper route to the same shape of result.

Top speed, Limited Kit

57 mph at 6,950 RPM Group K's figure for the bolt-on tier, which is head milling, carburettor true-boring and a re-pitched impeller with no porting.

Fuel burn at peak

44 litres per hour stock, 31.5 at cruise on the 38mm carburettors Group K's figures, given as 11.6 and 8.3 US gallons per hour. Quoted against a 15 gallon tank. No conditions are stated.

A sit-down cruiser build rather than a race entry, kept here for two facts the other records do not carry. The first is a measurement worth knowing before anybody pays for a carburettor service: Group K say the stock 40mm Mikuni measures only 37mm at the throat, and that true-boring is what opens it to a full 40. The second is the fuel figure, because this archive is otherwise all speed claims. They give stock burn at peak as 44 litres an hour against a 15 gallon tank, which is the number that decides how long a session can actually be. The framing on the page is that a well-sorted older two-stroke can match modern four-stroke feel for far less money, and that everything in the package is chosen around current 91 octane pump fuel, which they treat as noticeably less detonation-resistant than mid-1990s fuel. That last claim is theirs and is not checked here.

Whether any of it is legal in your class. A builder describing its own product, including by a class name, is not a check against a rulebook. Class legality holds the checks that name a section and a person.

Whether it would do the same on your machine. A quoted top speed is one builder's result on one craft, usually without the conditions, the rider weight or the fuel.