Sonic Fanon Wiki

BearfootTruck/Yamaha YZ series

Production Information
Manufacturer Yamaha Motor Company
Product Line YZ-series motorcycles
Model Various (see below)
Class Motocross bike
Technical Information
See comparison table below for technical information
Role(s) Motocross racing
  • Neutral
Other Information
Appearances The Fakest Things Alive, Sonicross, Chrome And Dirt
Original Creator Don Jones

The Yamaha YZ is a series of two-stroke and four-stroke motocross bikes produced by the Yamaha Motor Company from 1973 onwards.


Introduced in 1976, the Yamaha YZ400 (YZ400C) was thought to be little more than a repainted version of the Yamaha MX400. However, it incorporated a number of "works" parts that weren't on the MX400. The YZ400C had good performance, but the frame and handling were flawed.

In 1977, Yamaha redesigned the frame, engine and suspension. The YZ400D was an improvement over the earlier model, but handling was still lacking because the round swing arm tended to flex when cornering.

For 1978, the rear swing arm was replaced with a boxed aluminum swing arm. Suspension travel was increased as well. Out of the whole YZ400 range, the YZ400E is considered to be the best of the bunch.

1979 saw another redesign for the YZ400. The YZ400F (not to be confused with the four-stroke machine of the same name) got improved handling, FIM-type side number plates and a new engine. However, a number of people consider this engine to be a step backwards from the 1978 engine.


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BearfootTruck's Universe

Sonic brings home a 1978 YZ400 in The Fakest Things Alive. It is implied to be dirty and/or worn out, judging by what Sally said. By the time Sonic returns, Tails has made numerous modifications to the bike. For example, he replaced a number of parts with lightweight parts made of a titanium-magnacarbide alloy. Tails also put on a specially-modified kickstand & footpegs so that people as tall as Sonic can ride it more easily.

To personalize it, Tails painted it blue with red stripes & yellow fenders, put Sonic's name on the gas tank and the Sonic Team emblem on the side number plates. The newly-modified bike gets the nickname "Whirlwind" (not to be confused with the MTP-01 Whirlwind). However, Sonic doesn't get a chance to ride his sweet new moto-rocket because he has to run away from Sally, Amy, Rouge, Shadow & Antoine.

Technical Specs & Comparison
1976 Yamaha YZ400C.jpeg
1977 Yamaha YZ400D.jpeg
1978 Yamaha YZ400E.jpeg
1979 Yamaha YZ400F.jpeg
Engine 397 cc, two-stroke, one-cylinder, air-cooled, 7-port reed valve gasoline engine 396 cc, two-stroke, one-cylinder, air-cooled, 7-port reed valve gasoline engine
Bore Stroke: 85 mm x 70 mm 82 mm x 75 mm
Compression Ratio: 7.57:1 7.6:1 7.4:1
Power (crank) 34.40 hp @ 7,500 rpm Unknown Unknown 36.9 hp @ 7,000 rpm
Top Speed: Unknown
Carburetor: Mikuni VM38SS 38mm Mikuni VM38SC 38mm Mikuni VM38SS 38mm
Lubrication: Pre-mix (20:1)
Ignition: CDI magneto
Transmission: 5-speed manual with wet-plate clutch
Final Drive: #520 chain
Overall Length: Unknown
Overall Width: Unknown
Overall Height: Unknown
Seat Height: 34.84 in Unknown 36.1 in
Ground Clearance: Unknown 11.8 in
Wheelbase: 56.1 in Unknown 7.1 in
Dry Weight: Unknown 224 lb Unknown 225 lb
Wet Weight: 252 lb 229 lb 241 lb 239 lb
Suspension Front: Kayaba 36 mm Telescopic, coil spring, oil damped, spring pre-load fully adjustable, rebound compression damping force adjustable. Kayaba 38 mm Telescopic, coil spring, oil damped, spring pre-load fully adjustable, rebound compression damping force adjustable. Unknown
Suspension Rear: Monoshock, gas/oil damped, coil spring, spring pre-load fully adjustable, rebound damping force adjustable Monoshock, other specs unknown
Brakes Front: Drum, 130 mm Drum, dimensions unknown
Brakes Rear: Drum, 160mm Drum, dimensions unknown
Tires Front: 3.00-21
Tires Rear: 5.00-18 4.50-18 5.10-18
Gas mileage: Unknown
Fuel Tank Capacity: 2.1 gallons 2 gallons