I posted some of this in August, but would appreciate some opinions from you motorheads about the results:
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A couple of months ago, while I was changing shims on my valves, I decided to re-index the cams. I had already worked through what these changes would do to the timing. Jojje had confirmed that moving a cam one tooth would change the timing 15 degrees when measured at the crankshaft.
First I had the bike dyno'd with the cams in the stock position. Although the air/fuel ratio showed the bike to be running rich, I didn't want to fool with the jetting before a second dyno run with the cam timing changed. I was trying to see what making this one change would do.
Next, I advanced the exhaust cam one tooth (15 degrees at crank) and retarded the intake one tooth (15 degrees at the crank). Per my calculations, and using the cam timing specs for the 790 and 865 engines, this change would make the timing milder (like the 865), and therefore I expected to see the torque and hp curves change dramatically, hopefully providing more torque at a lower rpm. One would think that changing the valve overlap from 39 degrees to approx 9 degrees (similar to 865) would be a significant change.
The dyno results "before" and "after" were practically identical, which left me at a loss. I guess I would have expected either much worse or much better results, not same/same.
I did not attempt to calculate dynamic compression ratios for stock and modified versions, so I may have improved one area and worsened another with this mod.
Since the modified engine performed so much like the stock engine, I reinstalled the cams back to stock timing after riding it modified for approx 1000 miles.
Here's the two dyno runs for comparison. As stated before, both indicated a too-rich mixture.
http://s115.photobucket.com/albums/n...ent=Slide1.jpg
http://s115.photobucket.com/albums/n...ent=Slide1.jpg
Bob
