Help identifying part (spacer? special washer?)
Replacing the rear main seal on my R75/6. Got the seal in, oil pump gasket replaced, put the flywheel back on, then looked down at the floor and saw this. (The washer/spacer, not the penny -- that's just for scale.)
It's thicker than a standard washer, not a standard washer material and has an index mark on it, which tells me it's for sure important.
Hoping someone recognizes it and can tell me what is so I can figure out where it goes and when in the reassembly process I'll need to not drop it again.
Motor mount spacer?
I dunno. Part oft the clutch throwout rod?
Its thickness tells me that it came from a fastener location that had a high torque.
What size bolt is it for ?
[color=blue]Don't hide 'em, Ride 'em !!
The inside diameter is 9mm, which makes me think it goes with an 8mm bolt. It's a full 3 mm thick and brass(? or other yellow/gold metal) with a yellow paint mark on it that I don't think was added by the original owner. He did a nice job placing reference marks during the times he worked on the engine, but my impression is this looks like something from the factory.
The engine is still in the frame, but the gearbox and swingarm were removed. Neither of those has been dismantled beyond what it took to remove them.
I checked and the part does fit smoothly over the clutch pushrod, but nothing in the parts diagrams online or in my Haynes manual looks like a match.
Maybe it doesn't have anything to do with the bike and the garage gremlins are just messin' with ya?
I have a distant memory of such a thing. I think it was a clutch bolt spacer. Not sure. It may have fallen out of somewhere during a previous service. Are the ones in the airbox in position?
By the measurements, it's one of the washers that goes with the 12:00 and 6:00 cylinder head bolts, except that I didn't remove the cylinder heads. That leaves the gremlin theory on the table for sure. If my curiosity gets the better of me, I'll take a look. Meanwhile, I'm thinking it might have been used as a spacer behind the tab that holds the left airbox cover.
It certainly appears to be the "Spacer", Part Number 21 21 0 070 511; there are six(6) of them used in the clutch pack.
Their dimensions are: 4.0mm T X 8.50mm ID X 15.90mm OD.
They were used in the Slash 5 Series and if your Slash 6 is a very early build, it might have had them.
The Spacers are between the Clutch Pressure Ring and Pressure Plate, with the Clutch Plate 'sandwiched' between them; the Spacers allow room for the Clutch Plate.
The Clutch Countersunk Socket Head Bolts (6) that hold the Clutch assembly together, pass through them.
There's a high probability it is the one you're missing... time to open the Clutch back up !
Stuart, got to thinking about your 'Spacer' issue...
I am building up, a 1974 R90/6 and over morning coffee, thought of a way you can see if a 'Spacer' is missing !
Again, the six(6) Spacers were used with the Slash 5 Clutch; you might just have that Clutch in your Slash 6, if it is a very early build: 09/73, for example. Check the Headstock Badge for the Build Date or, if there are Slash 5 style switch gear on the perches, probably a good indicator. BMW often, 'used to depletion' build-line parts until updated parts arrived on the assembly line.
Here's an easy way to check the Clutch Pressure Plate, as the transmission is not installed: using and Inspection Mirror and bright flashlight, place the mirror on the 'shelf' above the Oil Pan and forward under the Ring Gear.
Manuver the mirror so as to view the Pressure Plate at one of the bolts, with any given one almost at the bottom, 6 o'clock position.
If you see the 'Spacers', it's a Slash 5 Pressure Plate and, uses six(6) of them. If you see a solid rim at any given bolt, it's a Slash 6 Pressure Plate and, no 'Spacers' are used as, the 4.0mm spacing has been build into the Pressure Plate; see the first picture, below.
Rotate the Clutch until you are between any two(2) bolts and, you'll see how the newer Pressure Plate is manufactured.
With a little 'fussing', you can even view the installed Clutch Plate; second picture below shows both.
Then on your motorräd, check all six(6) bolt locations to determine of one is absent a Spacer !
Wonderful pictures, thanks for them and the writeup. From the serial number and casting stamps, the date of manufacture is around Oct 1974. The pressure plate is for sure the /6 version, so I'm still left puzzling. If it weren't for the pandemic, this would have been my year for tech days. I'll sure be happy when those can come back.