From Cycle World. August 1976.

The story of O … OW72

Yamaha’s secret flat track engine: How and why.

The Story of O … OW72

 

The story of O … OW72

A nice story. No secrets. Kinda sad.

This manual first appeared in 1972. Here is the 1973 revised edition. Includes Section 11. XS750(650) Racing Special.

The OW72 motor was developed to take this and the then relevant associated tuning knowledge to another level.

Racing Part numbers referenced in this are found in the Yamaha Racing Parts Book.

 

Yamaha Racing Tips … mostly for the 2 stroke program … includes Section 11 XS750(650) Racing Special

 

YRT contents

 

YRT contents

 

YRT warning

 

Here are the sections. Relevant to XS650s are Sections 1 and 11 …

• Racing Tips. Section 1. Introduction …

1. Using a degree wheel,
2. Tips for cutting parts,
3. Cylinder Head mods,
4. Porting mods,
5. Piston mods,
6. Rotary Valve mods,
7. Con Rod mods,
8. Expansion Chambers,
9. Spark Plug selection,
10. Carb Adjustments

• Racing Tips. Section   2. JT1 and 2    Enduro, Motocross, Motocross Special
• Racing Tips. Section   3. LT2     Enduro, Motocross, Motocross Special
• Racing Tips. Section   4. AT2     Enduro, Motocross, Motocross Special
• Racing Tips. Section   5. CT2    Enduro, Motocross, Motocross Special
• Racing Tips. Section   6. DT2    Enduro, Motocross, Motocross Special
• Racing Tips. Section   7. RT2    Enduro, Motocross, Motocross Special
• Racing Tips. Section   8. LS2    Street, Special, TA125 Road Racer
• Racing Tips. Section   9. DS7   Street, TD3 Special
• Racing Tips. Section 10. R5     Street, TR3 Road Racer, TR3 Special
• Racing Tips. Section 11. XS650-750