Did some more stripping down of the JAPton head last week/weekend.
The more I tinker with this thing, the more issues I seem to be finding.
The rocker-arms live in their own little alloy box which is bolted onto the head - they rotate in pin-roller bearings which have their own mount so they're replaceable (I assume). The bearings in turn have spacers and a "distance ring" to keep their positions in the rocker-box, and the "End Washer" locates into a slot in the rocker-box. The trouble is - there's supposed to be a maximum of 1/64" of "end-play" (ie the "left-right" movement) of the rocker arm.... and well.... see the photos...
Photos:
1) Inlet lower half of rocker box
2) Exhaust lower half of rocker box
3) Inlet upper half of rocker box:
4) Exhaust upper half of rocker bx:
5) Right side of upper-half of rocker box (where ther push-rods and adjustment side of the rocker arm live)
6) Inlet rocker-arm in place 1:
7) Inlet rocker-arm in place 2:
8) Exhaust rocker arm in place 1:
9) Exhaust rocker arm in place 2:
10) Rocker box upper half (cleaned up)
11) Rocker box lower half (cleaned up a bit)
12) Rocker arm assembly broken down : (exhaust side)
I cleaned up the roller pins by stirring them in meths just to get the old oil off.
13) Bits :
(dissasembled rocker boxes, push rods, push rod covers)
14) Engine head sans rocker box (but with the last half of the valve covers still in place):
15)
16)
17) This is the diagram of the rocker-arm assembly from "The Book of the J.A.P.":
So - as (I hope) you can see - the rocker-arm assemblies
appear to be complete - AND YET - there's enough end-play in BOTH rocker arm assemblies to justify another washer between the (right side) bearing liner and the push-road end of the rocker arm!! See photos 6-7, and 7-8. The rocker arms can't actually fall out - but they're moving so much that.....
If you look at the photo of the upper part of the rocker-box - you can see where the push road has actually worn away the alloy of the rocker-box (photo 5, directly under the "R" in "Noral"). That little ledge is a "pathway" for oil to be drip-fed into the rocker-arm bearings (through the holes in the "distance piece"). That
can't be good!
You can see the little bearing pins floating around in photo 8!
What I can't figure out is how such a large discrepency could occur - it's not like the rocker-arms could have stretched nearly 2 millimeter in length!, and similarly - I can't see the spacers or distance ring being worn away that much either: to give that much end-play.
It's "possible" that the distance ring is wrong?? I suppose? The issue is that the engine was built up from "parts" - so I've no history on where each component came from: however to counter that.... these engines didn't change between '38 and '50 something (at all!), as I understand it, so I don't really see how any parts wouldn't be compatible.
Weirdly - the inlet rocker pin-roller bearings have 23 pins each, but the exhaust has only 22 pins each: I've no idea if that's by design (the books I have don't go into that much detail), or if the exhaust has lost a couple of pins.....
I seriously need to talk to a subject matter expert.
I'm going to be continuing to tear down the head: slowly: This is the first time I've delved this deep into this engine, and the last time I stripped a head it was on my first bike: my Mum's V50 Guzzi, and I had my Dad helping me (that was ..... err... IIRC I was 18....). I also like to clean and examine every part as I go - to check it's condition and to fully understand how it fits into the whole: so it tends to be a slow process.....
