Yamaha YZ400

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Yamaha YZ400
Production 76-79
Class Motorcross
397cc Air-cooled, 2-stroke, single
Bore / Stroke 85mm x 70 mm
Compression ratio 7.59 : 1
Top Speed 80 mph
Fuel System Mikuni VM36SC
Spark Plug NGK B8EV '76 , '77-78 , '79
Final Drive Chain: 520x105 [1]
Front Sprocket 15T
Rear Sprocket 50T
Frame Tubular steel double cradle
Front Tire 3.00-21 '76 , '77-78 , '79 [1]
Rear Tire 4.50-18 '76-79 [1]
Recommended Tire Pressure Front: 13 psi
Rear: 15 psi
Wheelbase 1450 mm[1]
Length 2145 mm[1]
Width 910 mm[1]
Height 1180 mm[1]
Seat Height 910 mm[1]
Weight 103 kg (wet)
Oil Capacity change: 1.1L
rebuild: 1.25 L
Recommended Oil Yamalube 10W-40
Related Yamaha MX400
Yamaha YZ400F
Manuals 1978 YZ400E Service Manual
1979 Yamaha YZ400F Service Manual
More Manuals

Reviews ·

This article is about the scooter, for the 1970s Motorcrosser, see Yamaha YZ400F for the recent version

1976 YZ400C[edit | edit source]

Take a 1975 MX400, paint it Yellow and add the spedo air forks and you end up with the 1976 YZ400C (I only saw 1, I swear it felt like an MX400).

  • SERIAL # 510-100101 - 102838

1977[edit | edit source]

A great leap forward in frame, engine and suspension design, the 1977 YZ400 was only lacking in it's ability to track corners because of the round tubular swing arm that caused too much flex. The monoshock was now encased inside the Monocoque frame that ran under the gas tank.

  • SERIAL # 1W4-000101 - 006720

1978[edit | edit source]

Expanding on a good thing, the 1978 YZ400 became stable with the box section aluminum swing arm and longer travel (at both ends). The bike was a bit heavy (tipping the scales around 240 lbs.) but long gone was the cracks in the frames, common with the previous (non-Monocoque) designs. The rake was also a bit long which made the 1977-1978 YZ400s better at cross-country than in motocross.

  • SERIAL # 2K8-000101 - 007406

1979[edit | edit source]

All good things must come to an end (which very much describes the 1979 YZ400). The rake was decreased to improve the handling in motocross but the 396cc engine was a step backwards (in this editor's opinion). This engine was only used on this bike and the 1980 IT425. Previous engines used the over-square 85x70 (397cc) design (even the SC500 used the same crank 95x70). This engine was 82x75 and never used again.

  • SERIAL # 2X5-000101 - N/A

See Also[edit | edit source]

References[edit | edit source]