Topic: favorite cam?

[Don R]

For those who auctually have installed and used an aftermarket cam in their 750 sohc, what cam did you use and how does it perform? Would you go bigger or smaller on the next one? What other changes does your engine have?

[Sam Green Racing]

125-60, torque monster.
125-70, top end monster.
DP295, torque and top end monster.
All with big bore, head, valves, carbs, exhaust and ignition.

Sam.

[bear]

125-60, torque monster.
125-70, top end monster.
DP295, torque and top end monster.
All with big bore, head, valves, carbs, exhaust and ignition.

Sam.

skite

Cheers,
Brian

[Sam Green Racing]

What does skite mean Brian, I tried to correct the spelling but it wouldn't let me, I't just cam up $%@*<

 

[Doctor_D]

Depends what you want to do with it.

On my 836cc, the 125-75 made more torque and horsepower than the 125-65 and has proven very tractable on the street.

[Bill/BentON Racing]

+1,Not giving up on /75 yet! We put 915cc kit in,75 cam back in,3rd run had 8-10 more H/P and over 5lbs more torque....NO fine tuning anything!
RC 295
RC 315
YOSH DAYTONA
NORRIS
ENGLE
MEGACYCLE 125/65
MEGACYCLE 125/75
None as good as they can be in conjunction with head work! Bill

[Don R]

Mine is a nice apparently low mile  K4 engine, I'm going with a ported head , valve job, milled .010, E-Bay 836 kit, K0 carbs, F timing advancer, and for now a rough looking header I think is a jardine. I may try to modify a stock F2 header to fit a K later.

The goal is a good street performance, short trip, fun to ride and look at bike. 1970's appearing resto-mod K0. It has to sound awesome and be reasonably fast although I may do a quarter mile just for fun, I won't be racing anyone. I want a nice cam but not one that's hard to live with long term. The two my brother have are large x huge, not sure they are what I would want. The previously mentioned RC315 and Ken Harmon F grind.

[Don R]

I was hoping for some real world input from someone that has auctually used some cams. So far it's been helpful thanks. Anyone else?

[MCRider]

Currently I'm going to try a WebCam #41. But no report yet. i will say from personal experience, i had a habit of putting too big a cam in my streetbikes. (no more) If you can at all contain yourself, for the street always go with torque over top end.  Keep the redline at stock, or only slightly above. On the street you seldom get there.

You'll have a lot more fun with less headaches. IMO

[754]

 I ran the 315 a long time...it had better low end than I expected... could have a bit to do with the Webers..
  BUT it is described as " Strong torque curve from the ground up, comes on low, and never quits" This one makes lots of horsepower. Very good for heavy street and altered bikes. Our favorite in street class. Has twisted us to many national records. Very streetable. Fair idle---quiet."
 I should mention that for a cam running .012 thou clearance, on all valves it is actually not that loud.
 The weiredest thing about it I found is that the Sorcerer or the triple actually uses that same cam.. FWIW..

[shinyribs]

.012" :oWow,thats a shocker. Now I'll show my ignorance...what is the Sorcerer.triple?

[754]

 The famous RC dragbikes are being restored right now....Sorcerer has 2 sohc motors and is blown, The triple 3 injected motors.. better known as the A,T,& SF

[Don R]

Dang, with .012 lash you'd think the lifter would just fall off the back side of the lobe. Maybe it sorta does.

Look at the ATSF and sorcerer thread for the triple. A classic example of if one engine is good two are better, three must be great!

It's a mechanical principle known as mores law, if more is better then too much is just right!

[Don R]

Thanks 754 I was a bit worried about the size of that cam. Some springs and retainers and we may be good to build. My car show is this weekend then I'll have time to talk to the local bike machinist guru about boring and milling. Then it's cam time.,

[MCRider]

From personal experience: when you're looking for a street cam, and a successful racer tells you their cam is very streetable...run.   

JMHO

[MRieck]

Depends what you want to do with it.

On my 836cc, the 125-75 made more torque and horsepower than the 125-65 and has proven very tractable on the street.

Exactly. The 127-75 is one of my all time favorite 750 cams as it has good lift and not so much duration. It keeps compression up which drives the torque (and HP) up. The 75 and 65  are dependent on a good flowing head....a stock head requires more duration but duration kills torque (which can be made up with more static compression....to a point). As Rob Muzzy said....You're not making power if the valves are open.
 Megacycle cams are not cheap....the only downside I know of.

[johno]

Hi Mike,
Whats the chance of you posting the cam specs for the main megacycle cams 125 / 60 /70/75, I could run it on the performancetrend engine analysis software at a nominated  displacement ( your call) and run all three cams to highlite the difference in the torque curves ( i'll post them)
Let me know ? 

Cheers Johno

PS Any other info would make the call more accurate, eg style of cam nose profile,  crank degrees at .200 lift makes this package boogy.

[Doctor_D]

                                                                                                        In o/c   Run-
Billet  Valve   Duration   Lobe                                                           Ex o/c   ning
Cam #   Lift    @.04"     center                                                         btc/abc  clrnc
        inches  degr  degr    Description and Application                     bbc/atc  inches
------------------------------------------------------------------------------
125-05  .340    246      104     OK w/stock piston & springs Best   19/47    .004
(125-00).330    247     104.5   w/HD springs. All around power     48/19    .004
125-01 regrind                increase w/smooth power band.
                              This was originally a production
                              road race profile
-------------------------------------------------------------------------------
125-25  .338    268   105     Use high CR pistons & P.M. or R/D    29/69    .005
(125-20).337    283   111.5   springs. Mid-range and top-end      73/30    .005
                              power, yet retains good low-end
-------------------------------------------------------------------------------
125-35  .407    266   105     Especially for '78 F2 models.              28/58    .005
(125-30).407    268   106     Great mid-range and top-end. Must  60/28    .005
                              use modified pistons and springs
                              Check carefully in CB K models
-------------------------------------------------------------------------------
125-65  .375    257   103.5   Best all around cam for street and 25/52    .004
(125-60).354    253   103.5   road w/K-836 kit and R/D or P.M.   50/23    .004
                              springs.  Strong mid-range great
                              top end.  Lobe clearancing needed
-------------------------------------------------------------------------------
125-75  .400    262   105     High performance street/road w/big 26/56    .005
(125-70).375    257   104.5   bore kit.  Use racing pistons &        53/24    .005
                              springs.  Mini sprint 3/8 and 1/4
                              mile.  More top-end power than our
                              #125-65.  Lobe clearancing needed
-------------------------------------------------------------------------------
125-95  .384    285   105.5   Drag race profile.  Must use           37/68    .005
(125-90).384    284   105     racing pistons & springs.  12:1 or  67/37    .005
                              more compression needed.  Not for
                              street use.  High R.P.M. cam
-------------------------------------------------------------------------------
125-x12 .430    270   105     Race profile.  Great throttle ctrl    30/60    .005
        .445    273   106.5   Maintain high cylinder pressure w/   63/30    .007
                              this cam.  Racing pistons and
                              springs required.  12:1 or more.
                              850cc and larger
-------------------------------------------------------------------------------
125-D   .345    265   105.5   Kenny Harman "D" grind.  OK w/     26/59    .005
billet  .325    280   110     stock pistons.  Use HD springs.         70/30    .005
                              Mid-range and some top-end
-------------------------------------------------------------------------------
125-F   .385    270   107     Kenny Harman "F" grind.  Use       28/62    .005
billet  .330    278   110     racing pistons & springs. Mini          69/29    .005
                              sprint, mid range and top-end
-------------------------------------------------------------------------------
125-NR  .350    252   106     NORRIS R profile.  MILD performance20/52    .005
        .350    252   106     increase.  Road/Road race.  SOME TQ   52/20    .005
                              ENGINE BUILDERS PREFER this profile
                              for small tracks in basically stock
                              motors.  P.M. Springs STRONGLY
                              RECOMMENDED
-------------------------------------------------------------------------------
125-N-T3.342    215   109.5   Turbo profile Norris design             2/37     .004
        .312    222   110     Turbo charged engines. Use race          41/1     .006
-------------------------------------------------------------------------------
Stock   .315    220           K7, F2 stock cams are different
K/F     .313    235
-------------------------------------------------------------------------------

[johno]

  I'm onto it,
Should be a great discussion point,
cheers D..... Johno

[MRieck]

johno....I apologize for not seeing your request to post #'s. Dave had my back....many thanks. I like the 125-75 as it has good lift but not a lot of duration. It works well with a ported head and produces great torque. Roll ons at 60 to 70mph are great.

[Greggo]

Subscribed!

[Don R]

Better than I had hoped for, thanks.

[Doctor_D]

I'm onto it,
Should be a great discussion point,
cheers D..... Johno

Good idea.

For goofs, I plugged the 125-x12 into my 836 file on Pipemax.  It moved the peaks up around 500 rpms over the 125-75, and made an additional 4hp at 9300 rpm.  Bumping the CR to 12.5:1 from 10.5:1 adds another 5hp, for a theoretical 101-107hp at the crank (depending on assumed VE%).

Can't wait to see what you come up with.

[Old Scrambler]

And now we are awaiting the supposed NEW cam profile in the CYCLE-X road-racer with the 915-kit.

[Doctor_D]

And now we are awaiting the supposed NEW cam profile in the CYCLE-X road-racer with the 915-kit.

I have it on good information that it is, or is closely based on, the Megacycle 125-x12.