Topic: Odd cam / rocker findings

[Garage_guy_chris]

I decided to pull the valve cover tonight and i am again confused. I have two odd things i dont know what to make out.

The Rocker arms:
 the rough parts of the casting appear to have been ground and cleaned up. Never heard of or seen this done before seems a little odd to me?!?





The cam:
there is a "R7" and a "AE" cast into it.





I did a few rough lift measurements to the cam while in the head and came out with some odd measurements;

base circles measure out at about 1.000" inch manual specifies  1.1016" - 1.1030"
lobes measeure out at around .315" intake and .315" exhaust manual specifies .315" intake and .286" exhaust

Im thinking this is a regrind of some sort but it seems odd the base circle is .100" undersize which for something like a cam seems like a ridiculous amount to grind away if in fact its a regrind....

Looking at my cam and comparing to ebay or whatever its obvious its been reduced there is no longer a grove between lobes its been ground down to its root diameter

[AJK]

The previous owner has tried to lighten the rockers for high rpm performance.

[754]

IMPORTANT..check and Write Down your valve clearances BEFORE taking apart.
Yes lightened rockers..motor sure has stuff done...

[Garage_guy_chris]

Ok the rockers are a little odd in my mind i dont think its going to effect a whole lot they seem in otherwise great condition. What does seem more odd and i would hope to get some insight on is the cam in this thing. I will probably have some more photos of later today

The cam:

I did a few rough lift measurements to the cam while in the head and came out with some odd measurements;

base circles measure out at about 1.000" inch manual specifies  1.1016" - 1.1030"
lobes measeure out at around 1.315", 1.315 - 1.000 = .315" intake and 1.315", 1.315 - 1.000 = .315" exhaust manual specifies .315" intake and .286" exhaust

Im thinking this is a regrind of some sort but it seems odd the base circle is .100" undersize which for something like a cam seems like a ridiculous amount to grind away if in fact its a regrind....

Looking at my cam and comparing to ebay or whatever its obvious its been reduced there is no longer a grove between lobes its been ground down to its root diameter

there is a "R7" and a "AE" cast into it.

[754]

It may be a mystery cam and have markings unknown to us on here, that is why you record the clearance.
 I hope you did the first check on cams,and removed the end washer....

[Garage_guy_chris]

I forgot to mention i did take off the end bolt and washer, nothing out of the ordinary just the 6 dash marks that are talked about and common on the factory castings.

I also looked at the flange for the sprocket there is nothing there either.  based solely on lift it appears to be a mild cam i will have to make up a rig to check out the duration and get an idea on opening / closing angles.  Im leaning towards using it provided the issue with the base circle being way undersized isnt going to cause a problem of throwing out the valve train / rocker geometry.  later today im gonna turn the engine over and watch what kind of arc the adjuster and valve stem follow it looks awfully steep with the valve closed

I will measure valve clearances as suggested on cyl #3 and #4 as i haven't touched that side yet.

Worst case i have to replace the cam. soon enough i should be able to draw the entire picture of what has been done to this engine. Maybe able to figure out what the previous owner was trying to accomplish.

[754]

Any wear on the valve cover caps ?
 What everything is indicating to me is a very labor intensive effort but low dollars spent, and not real radical (good for street)

[Garage_guy_chris]

Thanks for all the help it is much appreciated.

I would agree with this completely in every aspect of what i have found regarding the whole bike thus far.

What everything is indicating to me is a very labor intensive effort but low dollars spent, and not real radical (good for street)

I just checked. At the bottom or 6 o'clock position on the valve cover inside the inspection/adjustment openings there is contact marks on most and a groove on the #1 intake opening that seems to match up to the adjuster screw.

I can take and post photos if it helps.

[Jerry Rxman Griffin aka MuthaF'er]

What's the serial number of the engine?

[Garage_guy_chris]

the serial is CB750E-2350454 which puts it as a 1974 K4

If you see my other thread http://forums.sohc4.net/index.php?topic=132705.0  I have just discovered furthur problems which are now going to require a rebore or a cylinder swap.  So now i have lots of time to figure this out and sort everything