650 Performance


How the Best Ever XS650/750 Engines were Built

You can now purchase the XS650/750 Engine Modification Guide!

The XS650/750 Engine Modification Guide is now available for purchase!  It is a highly detailed, 83 page handbook 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:


The Reality Of XS650 Cylinder Head Porting
The Perfect XS750 Engine – Building The “Core”
Shell vs. Branch vs. Lillie – Dyno Graphs
Combustion Chamber
            Piston rings
            Combustion surface of the head
            Valve springs, guides, keepers, etc.
Carb Size Power Comparison – Dyno graphs
            Points ignition schematics
            ARD installation
Exhaust pipes
TT Pipes vs. Road Race Pipes – Dyno graphs
Lower End
Vent system modifications
An Incredible XS Street Setup
Forms & Misc.
Yamaha XS650 Engine Modification Guide [copy]
            Published August 1973 by Yamaha Racing  – 11 pages 

So you can get an idea of the Guide, I’ve included a sample for your review.  The download is comprised of the chapters dealing with optimizing the exhaust and includes 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.  Click "Buy Now" button and follow the instruction to order either through PayPal or credit card.  You'll then be sent a link to download the manual.  NOTE:  the link only lasts for 24 hours, so please don't delay.


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