850 Primary Chain Case confusion.

hello hello, hoping that I'm missing something stupid here. so, it's been now 12-18 months since I've stripped this Commando, had everything blasted, powder coated, polished yada yada. I didn't end up starting a build thread for this one.

As has happened to me before, I'm completely a miss with how this all goes back together. I hope I can drop this here and someone can just quickly tell me that everything is fine.

On my photo, there is kind of a race or a dished spacer that goes around the gearbox shaft. On all the Andover drawings I don't see this piece. Am I missing something? Perhaps I took this apart incorrectly. I remember the clutch sitting a lot more flush to the chain case, or like right up agains the circlip on the mainshaft.

This is my first commando, which I think is where my confusion comes from.

seanalex said:

On my photo, there is kind of a race or a dished spacer that goes around the gearbox shaft. On all the Andover drawings I don't see this piece. Am I missing something?

Click to expand...

No, its a later addition to the 850 MK2 after the initial start of the MK2 and is just a shield to attempt to keep oil away from the not very good seal that stops oil going out the back of the chaincase behind the clutch. As it looks it should not interfere with anything, I have one on a spare chaincase but never used it.

"INTRODUCED IN 1974 THIS CUP WAS INCORPORATED INTO THE SLIDING PLATE ASSEMBLY USED ON THE PRE MK3 COMMANDO PRIMARY CHAINCASE, THE IDEA BEING TO DEFLECT OIL AWAY TO PREVENT LEAKS. THIS PART ALONG WITH 060769 WAS SPOT WELDED INTO PLACE AT THE FACTORY, MAKING IT A CHALLENGE FOR THE HOME ENTHUSIASTS. GENUINE FACTORY STOCK."

"On my photo, there is kind of a race or a dished spacer that goes around the gearbox shaft."

Your verbiage describes this spacer (#54). It must be used up against the circlip.

thank you for the replies. just looks odd to me that there would be a void of space between the clutch backing plate and the case. Trying to figure out what parts I'm missing.

Yellow arrow?

Red arrow?

In the drawing Concours shows above, the stepped spacer #54 goes between the clutch and circlip. The stepped groove goes against the clip.

concours said:

View attachment 118645

Yellow arrow?

Red arrow?

Click to expand...

the red arrow

I get the spacer and that it sits onto the face of the circlip. Just odd to me that the rest of that dished cup is left empty. But it sounds like everyone is saying thats the intent of the design.

seanalex said:

I get the spacer and that it sits onto the face of the circlip. Just odd to me that the rest of that dished cup is left empty. But it sounds like everyone is saying thats the intent of the design.

Click to expand...

Yes, circlip 53 fits in the shaft groove, then spacer 54 recess over the circlip then shims as required then clutch.

Our ashley just did a video on the theme:

seanalex said:

the red arrow

I get the spacer and that it sits onto the face of the circlip. Just odd to me that the rest of that dished cup is left empty. But it sounds like everyone is saying thats the intent of the design.

Click to expand...

the dished addition is an oil deflector, as there was room to add it, as stated above. The lateral position of the clutch allowed it to be added, leavimg everything else in same positions.

all heard.

Most of my experience has been with pre commando chain cases, where the clutch sits pretty much right up against the case.

Thank you all for making sense of it.