The Yamaha KT100 is a 100 cc two-stroke cycle kart engine made by Yamaha that has also been adapted for ultralight aircraft use.[1]

A kart with a KT100 powerplant and a can type muffler
Type Single-cylinder, two-stroke engine
National origin Japan
Manufacturer Yamaha Motor Corporation
Major applications Kart racing
Ultralight aircraft

Design and development


The KT100 is a simple and rugged air-cooled engine that uses piston-ported intake induction with a Walbro WB-3A carburetor. The KT100 is a popular high-performance two-stroke kart racing engine. It comes in various forms used in many countries. The KT100J is slightly smaller with fewer options in comparison to its bigger brother, the KT100SE.[citation needed]

The KT100 is a very versatile engine using different exhaust systems and carburetors through a large range of classes. The KT100 can be tuned for most series and organizations with maximum and minimum rules.[citation needed]

Aircraft use


In the late 1970s and early 1980s the engine was adapted for use on ultralight aircraft. The ultralights of that era were lighter and had much lower wing loadings than today, making flight practical on the KT100's 15 hp (11 kW) developed at 10,000 rpm. In aircraft use it was usually equipped with a recoil starter and a belt reduction drive.[1]



Specifications (KT100S)


Data from Cliche[1] and Yamaha[2]

General characteristics


  • Valvetrain: Piston port
  • Fuel system: Walbro WB-3A carburetor
  • Oil system: premix 20:1 fuel to oil ratio
  • Cooling system: Air-cooled
  • Reduction gear: PTO to clutch or direct drive, belt drive in aircraft use


  • Power output: 15 hp (11 kW) at 10,000 rpm


  1. ^ a b c Cliche, Andre: Ultralight Aircraft Shopper's Guide 8th Edition, page G-8 Cybair Limited Publishing, 2001. ISBN 0-9680628-1-4
  2. ^ Yamaha Motor Corporation (2010). "2005 KT100 Specs". Retrieved 20 January 2010.