[Don Dorfman]

Your dyno guy may have one of the few dynos that aren't "happy".
Well is there such a thing as a "sad" dyno?
Calibrations can go both ways ya know.

The combination of parts is not very happy, simple as that.
Camshaft opening exhaust at 61° BBDC is of no help.
Just a shotgun guess the S&S 570 would be happier or one of many cams with ~40° ABDC IN closing cams with EX ~48-50 BBDC opening
You have an honest 10:1 compression ratio with a .030 HG unless the pistons are domed

 

[Don Dorfman]

agreed with the last 2 posts

Me too.
But that said anyone that wants some interesting insight about the Dynojet inertia dyno and how "accurate" it is should look into the history and the design. You will find references to the Yamaha Vmax.

More here:
http://v4musclebike.com/forums/showthread.php?t=9202

 

[Don Dorfman]

What are you running for fuel? At 10.6 I suspect it has a lot of spark backed out to control detonation. And as you back the spark down the horse power follows.

With a flat top piston at 98" and 79cc head he is at an honest 10:1 and the cam has a late 46 intake closing. Proper timing settings and there would be no timing pulled.
Does put the whole tune in question however and if the timing was set wrong it would pull timing and totally blow any power and torque production

 

[Don Dorfman]

For low end punch S&S 570. For a hot rod still decent torque down low S&S 585.
There are a whole gaggle of others but just be sure the intake close is between 42-44 preferred and the exhaust open ~50