Offering Specialized Engine Building & Tuning Information as well as CNC Porting Services for Hot Street or Race Engines
Offering Specialized Engine Building & Tuning Information as well as CNC Porting Services for Hot Street or Race Engines
Overview of the XS650/750 Engine Modification manual
Overview of the XS650/750 Engine Modification manual
Overview of the XS650/750 Engine Modification manual
Being an old guy, I remember the dirt track wars of the 70s when Triumph, BSA, Harley-Davidson, Yamaha, and even a few Hondas and Nortons battled it out every summer evening on dirt tracks all across America.
Eventually the Harley XR750 surpassed the Yamahas, and the best XS750 tuners such as Harry Lillie and Eddie Adkins were willing to
Being an old guy, I remember the dirt track wars of the 70s when Triumph, BSA, Harley-Davidson, Yamaha, and even a few Hondas and Nortons battled it out every summer evening on dirt tracks all across America.
Eventually the Harley XR750 surpassed the Yamahas, and the best XS750 tuners such as Harry Lillie and Eddie Adkins were willing to share their obsolete Yamaha secrets.
I was racing a XS750 (650) in AFM and AHRMA competition and was fortunate to meet and pick the brains of some of these premier XS tuners. Fortunately, I wrote everything down and put all the information and data into binders.
That information is what is in the manual. I have presented it in great detail: cams, carbs, exhaust, lower end, pistons, combustion chamber, tuning, and many more chapters laid out in great detail.
The Guide is a 105 page download, not a hard copy. Click the ENGINE MODIFICATION GUIDE button above to check out exactly what it contains.
overview of the CNC ported cylinder head
Overview of the XS650/750 Engine Modification manual
Overview of the XS650/750 Engine Modification manual
Bud Aksland, who built Kenny Roberts' engines, said the stock XS650 ports are larger than ideal to begin with, and any modification to increase flow must be subtle and carefully done. It's easy to go wrong. Simply enlarging the ports and rounding the sharp edges is a mistake, as the dyno will quickly reveal.
Harry Lillie ported the XS he
Bud Aksland, who built Kenny Roberts' engines, said the stock XS650 ports are larger than ideal to begin with, and any modification to increase flow must be subtle and carefully done. It's easy to go wrong. Simply enlarging the ports and rounding the sharp edges is a mistake, as the dyno will quickly reveal.
Harry Lillie ported the XS heads on the AMA-winning Yamahas of both Steve Eklund and Scott Pearson. In 1986 I purchased Steve's bike, and then when Harry retired in 1996 I purchased his stock of XS750 race components, including three additional fully modified cylinder heads.
In 2008 I had the heads flowed and selected the best one to be copied on a 5-axis CNC machine by CompetitionCNC (now located in North Carolina). For the next 10 years I sold copies of fully modified CNC-ported heads to racers all around the world.
The specials valves and other bits are gone, but the porting is now available for your XS650 cylinder head. It is an exact copy of the Harry Lillie head; accurate to .002", and delivers exceptionally linear and powerful performance on a hot street or race engine.
Click the CNC HEAD PORTING button above for additional information and current price.
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