Dual swingarm, rear axle gap

[dusty]

Hey guys,

Got an 02 M620 I'm rebuilding from a parts bin. Running into an issue on the rear axle where there's about 3-4mm of empty space along the spindle. Are the swing arms supposed to bend inwards to 'pinch' on the wheel, or am I missing a spacer? To clarify: according to the parts diagrams, I have all the correct pieces on the spindle (conical spacer, wheel assembly, caliper carrier), there's just.. more empty space. It almost looks like there's supposed to be another spacer on the swingarm side of the caliper carrier.

[Speeddog]

Swingarm is *not* supposed to bend inward.

Sounds like you've got some incorrect/missing parts.

[dusty]

Hm. Got two opinions now, one for and against the swing arm flexing to pinch.

Is it accurate then to say that, with all the parts on the spindle and the spindle mounted in the adjusting shoes, the entire assembly should fit between the swingarms with little to no side-to-side freeplay?

[ducpainter]

Hm. Got two opinions now, one for and against the swing arm flexing to pinch.

Is it accurate then to say that, with all the parts on the spindle and the spindle mounted in the adjusting shoes, the entire assembly should fit between the swingarms with little to no side-to-side freeplay?

Yes.

[Howie]

Agreed.  2-3mm gap is not good.

[dusty]

.. Y'anno, I was half-hoping to come back to a bunch of "no, that gap is totally fine" just so I could bolt it down. Oh well, do it once, do it right, and all that.

Getting more in depth, I feel reasonably confident that whatever is missing is on the rotor side of the wheel. On the sprocket side, the flanged inner bushing (710.1.041.1C) is perfectly flush with the conical spacer when the wheel is assembled, which I imagine is how it should be. If so, that'd narrow the problem down to something with the caliper carrier, I'd think. The carrier has a slightly extruded ring with its face ground flat on the inner side, which I'm guessing interfaces directly with the inner race of the wheel bearing, without any sort of washer between them (this also vertically aligns the seam of the caliper directly above the center of the rotor, so I think that'd be right?). I've looked around and can't seem to find any indication of a spacer between the swingarm or aligner shoe and the carrier, but the parts manual also shows a slightly different part than what mine looks like.



My carrier has no cylindrical extrusion on that block, just a flat face. Is it possible this is a two-piece part?

[Speeddog]

Caliper carrier has no cylindrical extrusion, the part drawing is incorrect (a copy/paste from prior configuration).

My best guess at this point is that you have a flanged inner bushing and conical spacer from the 5.5" wheel, which will not work with the sprocket carrier from the 4.5" wheel.

[dusty]

Well, there goes that easy solution. I won't say it's impossible that it's the wrong spacer set up, but this bike only came apart for paint, and prior to that it was a running bike - I certainly don't remember that much slop in the wheel, at least. Previous owner was a sweet homecare lady, too, who I don't think would have gotten into modifying the bike all that much.

[Speeddog]

You did say you were rebuilding from a parts bin, so to me that means "in 15 years, anything can happen". 

Has she owned it the whole time?

Some pictures would help, can you post some?

We've got some info:
http://www.ducatimonsterforum.org/index.php?topic=109.0
http://www.ducatimonsterforum.org/index.php?topic=72635.0

[dusty]

Haha! Yeah, I guess that was pretty ambiguous. To clarify with some bike history: I bought the bike in 2012 at ~3,700 miles from the lady, when it ran and rode fine. Ran into some financial problems and it got storaged until recently in 2018 (neglectful owner, tsk tsk), when it was brought back out (at 4,200 miles). I'm pretty sure it even had the factory rubber on it still until I swapped them out, but I can't be sure she owned it for its entire life prior to selling it. The 'parts bin' is really a half dozen large plastic containers full of parts that I filled as I took them off the bike. Rear tire size is the suggested 160/60ZR-17, which I think would only fit the 4.5"

I had a thought last night, and went digging through my old photo libraries. Found a picture among those I took ~2012 that was of the rear tire from almost directly behind the bike.


Interestingly, you can see the caliper carrier and conical spacer are flush to the swingarms - no gap there.

Between then and now, something has gone off, though, creating this annoying gap


With the carrier pressed against the wheel bearing, the seam of the caliper is directly above the rotor


With the wheel pressed fully to the left, seating the conical spacer against the swingarm, the rear sprocket is directly in line with the installed and torqued front sprocket - though it's worth noting that the sprocket is installed with the flat side inwards towards the motor, count to what the parts diagram recommends (which caused the front sprocket to be out of line with even the chain guard on the swingarm)


The conical spacer fits flush with the internal spacer


And both wheel bearings are flush with the edge of the wheel hub



The cush drive side of the sprocket carrier seems fine, but I don't really know what to look for here to be honest. Worth noting that the sprocket carrier does not sit flush against the wheel, and there is a ~3-4mm gap between the silver carrier and the black of the wheel.


Measuring the spacers gives a 44mm inner spacer and a 13.5mm conical spacer




Full album here, for higher resolution:
https://imgur.com/a/e2EB9CI

[Howie]

According to the parts fiche the same spacer and conical spacer are the same on the 750 and 900.  Unfortunately I have no idea why you now have the gap.  Was the bike stored with the wheel on?

[Speeddog]

Can you measure the width inside the swingarm, between the faces where the conical spacer sits on the left and the caliper bracket on the right?

[dusty]

Thanks for sticking it out with me guys, I know this probably isn't the highlight of your day.

Bike was stored entirely assembled, with the wheel on.

Measurement isn't as precise because my calipers don't go so high, but I measured a reasonably accurate ~241mm on a tape measure pulled taut and on a ruler

Edit: Interesting. I couldn't measure directly where the spindle would go because I needed something to keep the measurement perpendicular to the swing arm. Measuring at the raised threaded holes for the mudguard yielded a 242mm measurement, whereas measuring at the edge of the swing arm (sans chain adjuster) yielded the previous 241mm. It seems to be slightly pinched already?

[dusty]

Well, now I'm confused.

I was looking through the old photos from 2012, and noticed that the spindle was threaded to just a little beyond the nut on both sides. Out of curiousity, I went and put just the spindle through, and put the gold adjuster plates and the nuts onto the spindle.

It doesn't even come close to threading that far before the swingarm begins to pinch. In fact, there's about 3-4mm of thread left inside of the one nut, before it would roughly match how threaded the spindle appeared back in 2012. Normally I'd say that the swing arm was bent, but looking over the profile of the arms, there's no disruption or bubbling or creasing, and there's no damage to the welds - nothing to suggest the profile of the arms has been compromised in any way. Given the previous measurements of the span between the arms being more narrow towards their ends, how likely is it this unit has somehow been damaged?

[greenmonster]

"It doesn't even come close to threading that far before the swingarm begins to pinch."

Any wear marks on left inside of swing, indicating that conical spacer has been wrongly mounted
(conical side outwards), giving a couple of mm`s unwanted freeplay? And pinching chain adjusters?
IS the swing straight?