Topic: cam degreeing for a SOHC. What should it be?

[michrobi]

Here is the spec card that came with my 41 grind Webcam



Everything I've read says I should set the centers to the advertised cam degree. My spec sheet has no information other than the lash, lift and duration. Same on the Webcam catalog listing. Here are my current readings...

Intake
Open = 12° BTDC
Close = 42° ABDC
Lobe Center = 105°

Exhaust
Open = 47° BBDC
Close = 14° ATDC
Lobe Center = 106.5°

Overlap = 26°
Intake duration = 234°
Exhaust duration = 241°

What should I adjust the centers to be?

[MRieck]

 That's fine the way it is

[michrobi]

That's the best news I've heard in awhile.     I guess that's retarded just a little bit. So will probably favor the high end of the RPM band a skosh right?

[MRieck]

Yes... the higher the lobe center (retarded) the more it favors top end. You really can't do anything else with that cam because the lobe separation is fixed. 2 cam engine's allow you to really play around with lobe centers. 105 is very good for general street use....you retain good low end power but also maintain good top end. Every Yosh street cam on earth recommended 105 lobe centers

[HondaMan]

Yes... the higher the lobe center (retarded) the more it favors top end. You really can't do anything else with that cam because the lobe separation is fixed. 2 cam engine's allow you to really play around with lobe centers. 105 is very good for general street use....you retain good low end power but also maintain good top end. Every Yosh street cam on earth recommended 105 lobe centers

[start of hijack]
MRieck:
In your experience, what is the better brand of street cam for the CB750 today? I'm interested in longevity more than power, with perhaps a couple or 5 degrees of extra duration, no extra lift, particularly (adds loads I don't want or need, breathing is already very good here).
[end of hijack, sorry...]

[michrobi]

I can't seem to get the thing in line with my Martek 440 ignition. This current location puts the key groove on the cam at about 11:30. My ignition is turned as far counterclockwise as it will go, and it needs more. It's obviously out of time when I ride, spits and farts and backfires like crazy.

Will cam degree adjustment move the sweet spot on the ignition back and forth?

[MRieck]

I can't seem to get the thing in line with my Martek 440 ignition. This current location puts the key groove on the cam at about 11:30. My ignition is turned as far counterclockwise as it will go, and it needs more. It's obviously out of time when I ride, spits and farts and backfires like crazy.

Will cam degree adjustment move the sweet spot on the ignition back and forth?

No. Are you sure you were at absolute TDC when you set the cam?

[michrobi]

Pretty sure I was. The groove on the cam was way off 12 o clock before tho. It sat about 330 degrees when the crank was TDC I would say. Now it's at about 350-354 degrees at TDC. I'm going to adjust the valve lash and see what improves.

[michrobi]

No real improvement after a valve adjustment. Backfires at idle more than with gas. White smoke out the exhaust when I give throttle. It'll idle perfect for a few seconds, then get choppy and want to die, then good, etc etc. White smoke means it's too rich right? I've turned the air adjustment screws on my Mikuni 29mm smoothbore carbs from 1/4 turn to 2 turns and the white smoke doesn't change. It may just still be burning the rings in... I hope.

What's my next move?

[MRieck]

Yes... the higher the lobe center (retarded) the more it favors top end. You really can't do anything else with that cam because the lobe separation is fixed. 2 cam engine's allow you to really play around with lobe centers. 105 is very good for general street use....you retain good low end power but also maintain good top end. Every Yosh street cam on earth recommended 105 lobe centers

[start of hijack]
MRieck:
In your experience, what is the better brand of street cam for the CB750 today? I'm interested in longevity more than power, with perhaps a couple or 5 degrees of extra duration, no extra lift, particularly (adds loads I don't want or need, breathing is already very good here).
[end of hijack, sorry...]

Mark...sorry for the delay. You can have Megacycle regrind a cam to your specs....that's about as close as you will get with the specs you want. Otherwise the Web 41 is the closest cam to stock specs. I think an early F cam is what you would want.