The updated XS650/750 Engine Modification Guide is now available for purchase!
It is a highly detailed, 105 page download describing in very specific terms exactly how the best AMA tuners modified the XS650/750 engine for maximum performance. This information has been supplemented to reflect modern developments such as coatings, lubricants, ignition, etc.
While a primary focus of the Guide is building powerful and reliable race engines, plenty of ink is dedicated to street use. If your interest is a building a hot street bike, much of the data applies to the engine you will be building, and there is a specific chapter titled An Incredible XS Street Setup that directly addresses this topic.
Here are the chapter headings:
>How Much Power Does it Really Make? Shell vs. Branch vs. Lillie - Dyno Graphs
>The Perfect XS750 Engine – Building The “Core”
>The Reality Of XS650 Cylinder Head Porting - Comparative Flow Graph: Stock XS650 Cylinder Head vs. the Harry Lillie Modified Cylinder Head
>An Interview with Kenny Roberts' XS750 Engine Builder Bud Aksland
Piston rings & Total Seal Ring Installation
Combustion surface of the head
Valve springs, guides, keepers, etc.
>Camshafts and Cam Timing
>Carburetion & Intake Manifold
>Carb Size Power Comparison – 34mm vs. 36mm vs. 38mm Dyno Graphs
Points ignition schematics
>TT Pipes vs. Road Race Pipes – Dyno Graphs
>Vent system modifications
>An Incredible XS Street Setup
>The Mighty OU72 – Yamaha’s Answer to the H-D XR750
>Yamaha XS750 (650) Engine Modification Guide (COPY)
[Published August 1973 by Yamaha Racing]
>Forms & Miscellaneous
So you can get an idea of the Guide, I’ve included a sample chapter for your review. The download includes a chapter about optimizing the exhaust for your XS engine and also a dyno comparison of TT vs. road racing pipes. Even if you don’t purchase the Guide this data will be of real value to you. Here’s the link:
To purchase the guide, the contents of which represent the investment of countless development hours by the very best tuners and untold thousands of dollars in time and parts, you can do so for just $39.95.
Select "SHOP" above to purchase the Guide. When you pay, you will be sent a link to download the manual. NOTE: the link only lasts for 24 hours, so please don't delay.
Again, this is not a hard copy. It is a download. Every so often someone has had a problem with the process. If that happens, contact me and we'll figure it out.