Spot what is missing from the rocker hood and why??

[simonster]

Under the cam chain cover of my mid-renovation '72 500 k1, I have what appears to be four absent 6mm bolts. I've heard some models don't use them to hold the rocker shafts but these are threaded down and clearly was intended to hold bolts about 50 mm length. I've had her running under nil load, so confused as to why they are absent and how it runs apparently fairly smooth on tickover!! Any suggestions would be greatly received?

[Trigger]

These four bolts were added to stop the cam shaft springing/bouncing so much. You find these on later models and on the 550. Though a 550K1 doesn't have the bolts. 

[simonster]

Cheers trigger, but why would this cover have the bolt modification without the actual bolts being in place... I take it they aren't essential on the later models either?

[Trigger]

If it has the threads then someone may have forgot them.

[mickwinf]

if I recall correctly the earlier type have the 4 screws inside the breather cover, according to my 500/4 parts book 6x32mm part number 95700 06032 and the later 550s have an extra 4 studs with nuts to stop the rocker shafts turning in their housing and wearing the holes oval. I am sure Bryan or Oddjob will tell you for sure.

[Trigger]

Mick, They are not studs. The 550 has 4, 6x32 flanged bolts. But, you will have to ask one of the old boys the reason behind them. I am too young to know

[mickwinf]

trig I have just had a look at my 550k3 parts book and you are right about the flanged bolt, looks like they changed from the earlier panhead screws, but also show 4 cotter pins to hold the rocker shafts with a nut on the top which is the ones I remember, so there will be 8 holes inside the breather area instead of 4, can just be seen on the pic in the parts book.

[andy_c101]

See Service Bulletin #8.
Shows the addition of the 'cotter-pin' type retainers to prevent the rocker shafts rotating (on later rmodels)
Yes the four holes you show in your rocker cover photo are for four flanged retaining bolts, to attache to the cylinderhead;
later models as per the service bulletin introduce four more holes for the rockershaft retainers.
You do need to have bolts in your four holes on your rocker cover.

regards
Andy

[LesterPiglet]

If the holes are there something needs to fill them.
The missus tells me that and she isn't even an engineer.

[simonster]

Thanks for all the comments and advice. They do take 6mm bolts however one has been cross threaded in the past....but this doesn't explain why all four are missing!! I will tap out the thread and refit...cheers guys

[Trigger]

I suspect that they are missing because someone put the top cover on the cam cover, then bolted the cam cover on. This would explain the missing 6mm bolts. Other than that, i have no clue.