Rocker support/head/cylinder stud hex nuts

[GeorgeRyals]

Is it common for the four nuts holding the rocker support blocks to deform/flare out against the support blocks?
All 8 (both heads) nuts on my R90S are flared out with a sharp edge and even extruded metal around the studs. Seems that the nuts are significantly softer than the rocker support blocks.

GDR III

[pmdave]

No, the nuts should not be deforming. I've not seen this on my airheads. I suspect that someone installed the nuts upside down at some point, "chamfering" the holes in the rocker blocks. With the nuts on right side up (roundish side out) the edges of the nuts could be deforming. Or, the nuts might not have been hardened correctly.

Check the tops of the rocker blocks. They should be flat across the tops, around the holes. If not, you need "new" blocks, which should be available from the used parts suppliers. Otherwise, just get a new set of nuts.

I don't remember whether the rocker block nuts use flat washers. The parts breakdown illustration in the manual does not show washers, except for the top and bottom external nuts.

pmdave

[sgborgstrom]

I'd like to see a picture of this.
Considering the aluminum engine block the studs go into is considerably softer than either the nuts or studs, I would have expected them to pull out long before any deformation of the nuts could happen.

Very mysterious....

Steve

[Polarbear]

Extremely unusual thing here. Never seen this happen to anybody's airhead,etc. Maybe somebody did put it together wrong.

[AntonLargiader]

I've seen it, also on an R90S. I think this is a sign of poor heat-treating. I just replaced the nuts.

Those head nuts have a pretty thin contact ring. You can use the wider head nuts from later bikes but you would need to very slightly grind down the edge of the rocker arm. It's way harder to describe than it will be for you to visualize it looking at the valve gear.

[GeorgeRyals]

The rocker supports are not messed up in any way. I showed one of the deformed nuts to John at Bluemoon Cycles here in Alanta. He said he has seen it before and sometimes the flaring metal can actually contact the rocker arm.

I have a pretty good photo if I can figure out how to post it.

BTW the replacement nuts are $5.77 to $6.20 each depending on where you buy them. I looked at the new nuts with a bright light and 10X glass after torquing the heads, ther is no sign of deformation. There is another part number at $2.00 each. If my R90/6 has the same problem when I get into it, I heading to the Big ACE Hardware store for nuts.
George Ryals

[GeorgeRyals]

OOPS guess I should have resized the pic!

GDR III

[AntonLargiader]

OOPS guess I should have resized the pic!

So you're not fixing it because... ???

Make a note in the owner's manual about those Ace hardware nuts in case you ever sell the bike... :)

[GeorgeRyals]

Oh Yes I fixed it. I bought the BMW nuts at Bluemoon Cycle $6 apiece.
Now, don't besmurch Ace Hardware :-). The one here in Tucker, GA down the road from my office has every type, material and grade of fastener anyone would every need. Its a do it yourselfer's dream. Well they don't have Whitworth stuff for the limey bikes.

The only hesitation on using regular nuts instead of the BMW ones is that the BMW ones have a cylinderical section about 3 mm long turned on the end next t the rocker support. A standard nut may actually interfer with the rocker if a point of the hex wound up hanging out over the edge of the support block.

GDR III