FST 250 Worlds Fastest 250cc Dirt Bike

[John F2000]

In 1989 I built the Worlds Fastest Competitive dirt bike. Now 30 years later I am sharing the story of an amazing motorcycle and hopefully soon will race it in one of the upcoming NORRA events.

Prior to building the FST 250, some at the time referred to it as Relampago, I developed a supercharged 560cc Rotax motor to run in an ATK. In the middle of the project I came across an amazing motor, the 256cc inline twin by Rotax. I fell in love with the motor and decided to build a dirt bike around it to race the 1989 Baja 1000. Throughout this thread I will post some pictures of the restoration of the bike, videos of it coming back to life, and some fun stories of how the bike came to existence. But most important what a wild ride it is to climb on a 16,000 rpm, 90 hp inline twin dirt bike, with a top speed on a fire road with competitive gearing and ready to race at over 121 mph!

FST 250 Specifications:

90 HP inline twin Rotax
Dual Power Valves
Digital Ignition
Dual Dellorto Carburators
Quick change 6 speed gear box
Dry Clutch
CJ Frame
White Power Suspension
228 lbs
Fuel Capacity 3.8 Gallons

 

[Josh 8]

I have always had the itch for atk’s. I got to ride a 560 years ago for a magazine review as I was a avid kx 500 rider and had a strong one to compare it too. We drag raced the bikes together and the atk would pull the kx through the gears by a slight amount then just keep going past on the top end to well over a 100 once the kx was out of gearing. Gone!

I was in disbelief a old school pump gas 4 stroke could do that.

I had to take a double take on the photo to understand the expansion chambers. Twins. That’s space tech there! I think I remember reading about that bike in dirt bike magazine back in 89’.