Topic: My Cam Looks Retarded...

[HondaMan]

Piston stop on the way...  but originally checked/set TDC with dial indicator when head was off, and torqued with stud spacers on.

Similar to this photo by Brantley  http://forums.sohc4.net/index.php?topic=112544.0

Only in the center, not the edge of piston.
oh by the way...   my cam WAS retarded.

Eliminating any doubt...  I sure appreciate all the expert opinions here...

That will help, but had a thought: wasn't the Kenny Harmon "D" grind for turbo engines? The late exhaust closure suggests that. This method is used to ensure the inlet, under pressure, has time to fully charge the cylinder and remove all exhaust gases, while the late closure keeps the compression pressures down a bit. Without a late exhaust closure on a turbo'd engine, you usually have to lower the overall compression (like by using extra cylinder base gaskets, etc.) to control those numbers.

[Retro Rocket]

Kenny Harmon "D" grind

                                                                   In o/c
                                                                    Ex o/c
         Valve   Durat-                                             btc/abc
Cam      lift    ion       Description                              bbc/atc
---------------------------------------------------------------------------
D        .345    277       A famous grind. Excellent for a major HP  32/65
         .325    294       increase, yet a wide range of use. Long   77/37
                           exhaust duration for sustained high speed
                           cruising without excess combustion chamber
                           temperature. May be used with stock
                           springs if desired.

[70CB750]

This got me thinking - bad habit, I know  - the K0 has the power band right on the money at 4000 rpm and I love it.

Now the F engine if I stick with the original cam, it will have similar kick @ 6000 rpms.  According to gear calculator (for K, not for F but it will not be far):

18/48
rpms   1st 2nd  3rd  4th 5th
6,000   36   52   67   81   95
16/48
6,000   32   46   60   72   85
15/48
6,000   30   44   56   68   79
14/43
6,000   31   45   58   71   83

Hmm, seems like it does not make much sense to go that way, to make the F be more streetable, or at least legal for pete's sake - 70mph is the highest speed limit in our area.


Edit:  14/43 is what JT lists as stock for 78 F2 - I quess Honda did go through the same process.

Yeah, the 14/43 combo on the "F" bikes made them very 'buzzy" in the touring crowd's minds (3.07 final drive ratio), and installing a 15t front was common back then if you were pushing a Vetter fairing. This made it close to the K0/K1 gearing, much more pleasing to the ear, but then it was almost 1000 RPM off of the bottom end of the "F" powerband. This contributed greatly to the lost sales in the post-1976 SOHC4 750 bikes (IMO), as we heard MUCH about it from those who had worn out their first 750, then bought another, only to be disappointed on the open road. Historical trivia...

Thank you, Mark, your points are not lost on me.  I am going with adjustable cam gear to clock the camshaft - after I am done with the valve job.