128cc (7.781ci) - 20hp
57mm x 49.5mm high rev mill

 -- alt conf --

121cc (7.384ci) - 20hp
61mm x 41.4mm high rev mill

Intake:
 HP * 1.62 = CFM

 20HP * 1.62 = 32.4CFM of flow needed to hit target

 Volumetric Efficiency:
  CFM = (ci * RPM * VE) / 3456
  -or-
  RPM = (CFM * 3456) / (ci * VE) 

  (32.4CFM * 3456) / (7.781ci * 60% VE) = 20HP @ 24k RPM 
   80% VE = 20HP @ 18k RPM
   90% VE = 20HP @ 16k RPM
  100% VE = 20HP @ 14.4k RPM
  110% VE = 20HP @ 13k RPM 
  115% VE = 20HP @ 12.5k RPM

 Intake Valve:
  Area of a circle = (pi * d^2) / 4
  Valve CFM estimate = (area of valve / 30) * 1.62
  Add 10% for dual valve setups

  2 x 19mm intake = 33.7CFM
  2 x 20mm intake = 37.3CFM
  2 x 21mm intake = 41.1CFM
  1 x 27mm intake = 30.9CFM
  1 x 28mm intake = 33.2CFM
  1 x 29mm intake = 35.6CFM
  1 x 30mm intake = 38.2CFM

  Intake Flow Mach Number:
   http://www.rbracing-rsr.com/machcalc.html
   The flow velocity shouldn't exceed Mach .6 or VE will fall off hard without adjusting the cam profile for late intake closing.  A Mach index of .6 is where you hit peak VE.  Increasing lift decreases the Mach index.

   Mach numbers estimated using 'z40' (6.92mm lift) cam.
            10k 11k 12k 13k 14k 15k 16k RPM
   2 x 19mm .39 .42 .47  .5 .54 .58 .62
   2 x 20mm .37  .4 .44 .48 .51 .54 .59
   2 x 21mm .35 .38 .42 .45 .49 .52 .56
   1 x 27mm .54 .6  .65 .71 .76 .81 .87
   1 x 30mm .49 .54 .57 .63 .68 .73 .78

 Intake Tract Design:
  Intake Tract Length:
   http://www.jrbranson.com/HondaRacer/honda/intake_system_design.htm
   Intake length inches = 90 / (RPM / 1000)
   90 / (14500 / 1000) = 6.2 inches 

  Tuned Runner Theory:
   http://auto.howstuffworks.com/question517.htm
   Intake lenght in feet = ((60 / RPM) * ((720 - intake duration) / 360) * 1300) / 2
   EST 230 deg duration, 14500 RPM target - 3.6609 feet 'ideal' length
   The theory allows for the intake length to be shortend by power of 2 intervals to get something more usable.  A power of 8 reduction puts the target at 5.5 inches, close to the alt theory above.  This method takes cam timing into effect however, rather than JUST RPM.

   A power of 4 reduction puts the intake tract at just under 11 inches.

   Also note the 1300f/s estimate used in the formula varies dependant on intake air temp, will need running temp data to refine this calculation.

  Other Intake Links:
   http://www.wallaceracing.com/runnertorquecalc.php

 Intake Valve to Bore Area ratios
  http://www.visi.com/~moperfserv/ducati997.htm
  This isn't too reassuring to look at.  The valve to bore area ratio of the first gen 916 Strada motor was .2465.  A classic Chevy 350 looks better with .25 even, by 2000 Japanese sport bikes were pushing the .35 mark.

  Valves Bore  Av/Ab Example Application
  2 x 19 52.4 0.2630 SDG 3v 107
  1 x 19 39   0.2373 Honda CRF50
  1 x 23 47   0.2395 Honda CRF70
  1 x 23 52.4 0.1927 GPX 125
  1 x 27 52.4 0.2655 Big Valve Head
  1 x 27 54   0.2500 Big Valve Head 114 / 131 kit
  2 x 21 54   0.3025 Daytona DOHC 119
  1 x 27 57   0.2244 145 kit
  1 x 27 61   0.1959 Edge of the envelope for Lifan Monster stud spacing
  1 x 31 60   0.2669
  1 x 31 52.4 0.3500
  2 x 22 60   0.2869

  Choked up no matter which way you look at it, unless you find some way to make that 31mm intake valve setup fit in a stock import bore, or you start with the Daytona DOHC head.  This would help explain why as most motors get bigger and bigger, they turn into torquers.  For this motor to really work, I'm going to have to get the valve to bore ratio problem sorted.

 Exhaust Valve:
  http://www.rbracing-rsr.com/machcalc.html
  Exhaust should flow 65% to 80% of Intake (Not sure if this is based on peak flow potential, or flow at peak HP).

  2 x 19mm intake == 21.9CFM to 26.7CFM exhaust valve flow
  2 x 20mm intake == 24.2CFM to 29.8CFM exahust valve flow
  2 x 21mm intake == 26.7CFM to 32.8CFM exhaust valve flow

  22mm exhaust = 20.5CFM
  23mm exhaust = 22.4CFM
  24mm exhaust = 24.4CFM
  25mm exhaust = 26.5CFM

 High RPM Running:
  http://www.webcalc.net/calc/0752_pistonspeed.php
  The number I've always seen is not to exceed 4000f/s mean piston speed with cast pistons, although you can supposedly  push that up to 7000f/s with high quality piston, rings, rod, etc.

          12k  14k  15k  16k RPM 
  41.4mm 3266 3810 4082 4354
  49.5mm 3896 4545 4870 5194
  54mm   4250 4958 5312 5666
  55.5mm 4370 5098 5462 5826
  57.5mm 4526 5280 5657 6034

 Rod Ratios:
  http://victorylibrary.com/mopar/cam-tech-c.htm
  A rod ratio of 1.75:1 seems to be the theoretical 'sweet spot' according to this article.

  http://www.sigmaperformance.com/748-853.html
  Here the suggestion is a longer rod, 2:1 to match the magical 996R motor.  They also suggest a far more oversquare motor, 1.55:1 bore to stroke, putting a 64mm bore ontop of a 41.4mm crank to hit 133cc with the right ratio.  Destroke a crank down to 37mm to match a 57mm bore?  The world's twistiest 95cc motor?  This recomendation is based on a 90 deg V-Twin, so that may change things going to a single.

  One thing that may be good to steal from Ducati is the SuperMono's balancer setup.  The SuperMono used a stock crank from a twin, the vertical cylinder's con rod was connected to a lever rather than a piston.  Leaving this setup in place let the Mono get the benifits of an L Twin's natural primary balance.  Given how hard this motor will need to spin, that might not be a bad idea to incorporate.  It'll require a custom crank, and a forked big end rod to stradle the main rod.  The machinging for the top of the cases shouldn't be too bad, others have bolted whole functional cylinders on top, this won't need anywhere near that strength.

 Bore Ratios:
  As noted above, Ducati runs a way oversquare motor, 1.55:1 bore to stroke typically.  Other examples:
   Ducati 748R - 1.43:1 88 x 61.5
   Ducati 749R - 1.74:1 94 x 54
   Ducati 996R - 1.57:1 
   Ducati 999R - 1.77:1 104 x 58.5
   Ducati 1098 - 1.61:1 104 x 64.7
   Honda CBR600RR - 1.58:1 - 67 x 42.5 
   Honda CBR1000RR - 1.33:1 - 75 x 56.5
   Honda CRF150R - 1.51:1 - 66 x 43.7
   Honda CRF250R - 1.49:1 - 78 x 52.2
   Honda CRF450R - 1.55:1 - 96 x 62.1
   KTM 250 SX-F - 1.38:1 76 x 55
   KTM 450 SX-F - 1.60:1 97 x 60.8
   KTM 450 EXC-G - 1.24:1 89 x 72
   KTM 950 Supermoto - 1.67:1 100 x 60
   Suzuki GSX-R600 - 1.58:1 67 x 42.5
   Suzuki GSX-R750 - 1.44:1 70 x 48.7
   Suzuki GSX-R1000 - 1.24:1 73.4 x 59
   Suzuki Hayabusa - 1.29:1 81 x 63
   Suzuki RM-Z250 - 1.44:1 77 x 53.6
   Suzuki RM-Z450 - 1.52:1 95.5 x 62.8
   Yamaha YZF-R6 - 1.58:1 67 x 42.5
   Yamaha YZF-R1 - 1.44:1 77 x 53.6
   Yamaha YZ250F - 1.44:1 77 x 53.6
   Yamaha YZ450F - 1.50:1  95 x 63.4

  Most hover around 1.5:1, with lower ratios being advertised as torquers compared to the rest.