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Yamaha IT 425

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Make Model

Yamaha IT 425

Year

1980

Engine

Two stroke, single cylinder, read valve

Capacity

425 cc / 25.9 cu-in
Bore x Stroke 85 x 75 mm
Cooling System Air cooled
Compression Ratio 7.3;1

Induction

38mm VM38SS Mikuni carburetor

Ignition 

CDI
Starting Kick

Max Power

36.9 hp / 27.5 kW @ 6000 rpm  (rear tyre

Max Torque

31 lb-ft / 4.23 kg-m @ 5500 rpm
Clutch Wet, multi-plate

Transmission

5 Speed 
Final Drive Chain

Front Suspension

43mm Telescopic adjustable forks, 300mm wheel travel
Front Wheel Travel 250 mm / 9.8 in

Rear Suspension

Mono shock, adjustable spring preload and rebound damping, 300mm wheel travel
Rear Wheel Travel 250 mm / 9.8 in

Front Brakes

Drum

Rear Brakes

Drum

Front Tyre

3.00 -21

Rear Tyre

150/80 -18
Rake 29.5°
Trail 125 mm / 4.9 in
Wheelbase 1430 mm / 56.2 in
Ground Clearance 285 mm / 11.2 in

Dry Weight

111 kg / 244.7 in

Fuel Capacity

13.6 Litres / 3.5 US gal
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The IT425 which for the first time brought 'professional'-type performance within the grasp of anybody able or willing to expend approximately £1,200 in pursuit of his chosen pastime of enduro racing (or fastgreen-laning).
Based on the YZ400 moto-crosser, with a triangulated rear frame and a single monoshock damper with variable loading, the IT (for International Trial) 425 had an air-assisted leading-axle front fork and very complete equipment, running even to a small headlamp powered from a flywheel generator.

The engine, however, tucked away in a lightweight, 56in-wheelbase chassis, justifiably took most attention on account of both its all-black good looks and its specification which, while keeping to nothing more outlandish than a five-port layout, with reed valve for induction, managed to churn out 46 bhp at 6,500 rpm, providing plenty of outright speed