Topic: Advancing the cam 5 degrees, per Hondaman: How to?

[Scott S]

 I did a search, but all I get are results about timing, etc.

 I know I have to slot the cam sprocket, but how do I know how much?

 I figure I'll need a degree wheel of some type. Do I attach it down on the engine where I normally time the igniton?

 Is there a way to use the T and F marks to do this?

 Does ignition timing need to be altered?

 Degreeing the cam for Dummies, please! 
 

[Greggo]

Subscribed!  I'd like to see the answer to this.  I assume you're doing this on the 500?

[bwaller]

Slot the sprocket 3 or 4 degrees each direction.

Attach the degree wheel (at least 12"diameter) on the alternator side.

You're best to make a positive piston stop to find true TDC. The marks on the engine case/advance mechanism can be off, don't use them. You can make one out of an old spark plug and a long bolt.




You'll also need a dial indicator to indicate off the spring retainer on the 550.





Search for "cam degreeing" by scondon. It seems to me Sean wrote a good how-to.

Ignition timing is separate, unrelated to this operation.

[Scott S]

Slot the sprocket 3 or 4 degrees each direction.

But how do I determine how much is 3 or 4 degrees?

Attach the degree wheel (at least 12"diameter) on the alternator side.

You're best to make a positive piston stop to find true TDC. The marks on the engine case/advance mechanism can be off, don't use them. You can make one out of an old spark plug and a long bolt.




You'll also need a dial indicator to indicate off the spring retainer on the 550.

Indicate for what?





Search for "cam degreeing" by scondon. It seems to me Sean wrote a good how-to.

Ignition timing is separate, unrelated to this operation.

 I understand that....sorta. But if the cam is opening the valves earlier, and the spark plugs are firing at the stock time, what effect does that have, if any? Remember.....cam degreeing for dummies!

 This is on a '78 CB550 with a CB650 cam, BTW

[Scott S]

 Found it: http://forums.sohc4.net/index.php?topic=3148.msg23634#msg23634

 Should be very helpful. Need to read it carefully and come back with some more questions...

[Scott S]

 Quoting myself here: " I understand that....sorta. But if the cam is opening the valves earlier, and the spark plugs are firing at the stock time, what effect does that have, if any? Remember.....cam degreeing for dummies!"

 Took the dog for a walk and thought about this. I think I understand....
 Even if the valves are opening sooner or later than stock (because of cam timing), the ignition still fires at TDC (are at whatever the stock advance mechanism is set to fire at). The engine is just pulling in air/fuel a little sooner or later because of the degreed cam. Right?
 How, exactly, does that affect power?

[dave500]

if your going as far as to change your cam tiiming your looking for more power?dont use the stock timing settings for the ignition,,it will run ok and good as it is but if you just advance the timing little by little past those two full advance marks untill it pings,then back it off,youll pickup some power and economy even with the cam in the standard timing,,this might cause a little kick back when starting as it also moves the initial advance up,,you can leave the kill switch off as you crank then when the engine is spinning well during starting flick the kill switch to run,give it a go its easy to back the ignition off again somewhat but still be more advanced than the stock settings.

[dave500]

the valve overlap,,that is when both of the valves are open together,just a little bit for a little while occurs at the finish of the exhaust stroke and the begining of the intake stroke,at a certain rpm this feature actually forces new fuel through and helps to purge the spent gasses to a degree,,wild or hot cams do this more,,and the low rev power and idle go bad,stock cams are designed so this effect is at a certain rpm band where its most usefull or better for all around drivability,,this goes for any four stroke engine,,without changing the cam grind to move this effect in the rpm band if the cam is retimed or repositioned this effect can be moved so it happens at a higher or lower rpm,many car engines have simply moved the timing mark or key way on the cam gear as smog laws encroached pre efi,,the actual cam is the same,hope this helps.

[bwaller]

Without looking it up, the stock cam #'s are 5-35-35-5? I know HM suggested the 5 degree advance. I wonder if it actually can be felt through the seat of the pants?