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A hole drilled into the center of a rocker shaft adjustment slot, but why?

ausman1000

ausman1000

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I recently acquired a complete cam box assembly from a 68-70 CB350 (fat cam version) and discovered both left and right front rocker shafts have had this alteration performed. Not only is there a shallow hole drilled into the center but the same end has also been ground down reducing the amount of exposure.

Any of you smarter peeps out there have any good guesses as to why? Hmm...

box.jpg boxx.jpg
 
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R/H exhaust rocker adjuster decided to dress up as a pilot jet for Halloween?

That’s uh, strange.


- 1972 CL350
- 1985 VF700F
 
Since it is a shallow hole, my guess is for a modified blade screw driver with a small spigot in the middle filed on the end.
should make adjusting easier and prevent the blade slipping out.
I have just been through this on my engine build and a couple of times the screw driver blade slipped while adjusting the rocker clearance.

gary
Auckland
 
GaryJames said:
Since it is a shallow hole, my guess is for a modified blade screw driver with a small spigot in the middle filed on the end.
should make adjusting easier and prevent the blade slipping out.
I have just been through this on my engine build and a couple of times the screw driver blade slipped while adjusting the rocker clearance.

gary
Auckland
Click to expand...

Interesting idea, and that makes sense, however I wonder why it was only done on the exhaust shafts and not on the intake shafts?
 
Just now seeing this, and I've never seen it before so I'm wondering the same things - why, and why only the exhaust. These bikes have been around so long that many things can and probably have happened to them that we'll never know the reasons for, or just never know... but it damn sure is weird. And those shafts are not soft metal, they're hardened to take the load of a rocker arm flailing away at 9500 rpm regularly.
 
could they be using a special adjustment tool with centering pin? you know how flat blades like to slide off and cause damage.
 
DSC03616.jpg
Different finish compared to the non drilled parts. They drilled pieces show very little wear, replacements for originals perhaps. This engine also gave me 4 new inner valve springs. It was either excellent parts or ugly ones but you roll the dice .... will come out even ... eventually .... maybe .... oh forgot I sold a 400F tank from this deal for 30% of what the whole deal cost. I may come out ahead!
 
The holes in the ones I have are not consistent enough to be part of the machining process and don't even look like anything for a special screw driver to work with.

How about a racer looking to save weight!

I wonder if they are some Thailand specials .....
 
Received another cam box assembly today with some more 'hole' version rocker shafts. Like Boomer said, probably the early motors have them. Box came off a SL350 per seller.

h.jpg hh.jpg
 
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You sure I can't interest you in some of my parts and projects?
 
MrPepper said:
You sure I can't interest you in some of my parts and projects?
Click to expand...
Haha, don't encourage me that's not nice :lol:

I do buy quite often but the reason behind it is to build up a spare parts inventory for both bikes we have here in the garage, the CB350 K1 and K2. I have multiples of quite a few things and will keep the best and move the rest as I find time.

Definitely not looking for any more projects :eek:
 
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