900 Cush Drive Question.

[koko64]

Swapped out the cush drive on my '95 900.
Picked up a used cush drive (sprocket holder part) as mine was displaying movement between the pins and bushes. There was always some movement which I put down to wear, but I suspect that mismatched parts could be the reason.

I found the used "new" drive to be a nice tight fit into the bushes. I also noted that there was 5mm more clearance between my swingarm and the sprocket nuts which was quite welcome. The "new" cush drive sits into the hub more fully and is about 5mm narrower.

Did the factory change the sprocket carrier/cush drive for more clearance at any stage?
I am thinking that my bike came with a miss matched part off a bike with a steel swingarm, an earlier cush drive, or one from a 750 with a narrower wheel/hub? The "newer" part fits better with slightly thicker pins (about 1mm) and sits into the hub snugly and with better clearance. The factory did go to thicker pins sometime in the mid nineties IIRC.

The vendor is a "grey" importer so I would not be surprised at some swapping of parts to get the bikes prepped.

[ducpainter]

I was not aware of different cush drive inserts. I'm also not aware of any changes to the pins or carriers for 5" wheels.

Did you buy your bike new?

[koko64]

5 years ago with 4500 miles. Its always had bush/pin play.
Both cush drives with pins removed and flat on the bench, "old" one 5mm taller. Pins the same but for a mm in thickness at the bush end. I think they were beefed up due to some breaking.
Old cush gave only 2-3mm sprocket nut to swingarm clearance, new one has 7-8mm which is great. Hows the clearance on yours?

[ducpainter]

It's never been an issue...

I'll measure it for you a bit later when it warms up...22F right now.

[Speeddog]

I'm pretty sure there's 3 different carriers, and I may have one of each to measure.

[koko64]

Thanks. You might save Nate going out to the shed in the cold.   

[Speeddog]

I suspected there were 3 kinds, but I've only found 2.

M750 - 13mm offset

ST2, M900ie - 18.5mm offset

I suspected that the M900ie was going to be the '3rd' kind, as it's the one that has the oddball symmetrical front sprocket.
But it was the same as the ST2.

Standard Ducati front sprocket produces a 10mm offset when you flip it.

Why the carrier difference is 6.5mm vs. the 10mm at the sprocket?
Who knows....

Drive pin 82110091A diameter is 0.629" (15.98mm)

Cush drive 70090051A inner diameter is 0.642" (16.30mm)

Both of those are brand new in the bag.

Pic of how I measured:

[koko64]

The one I removed was 18mm and the one that went on was 13mm. So that accounts for the 5mm. Maybe its got to do with tyre/wheel width and chain clearance. The pins were a mil bigger diameter on the 13mm offset carrier.

[koko64]

The one I removed was 18mm and the one that went on was 13mm. So that accounts for the 5mm. Maybe its got to do with tyre/wheel width and chain clearance. The pins were a mil bigger diameter on the 13mm offset carrier.

Edit:
According to LT Snyder, it was the threaded part of the cush drive pins that goes into the carrier that was increased in diameter. So I guess the pins were worn ( by 4500 miles).

So I thought about swapping the pins to the old carrier. (EDIT). Of course this will not work due to the pins having a shorter length on the sprocket side by at least 5mm. This means it is a 750 version as SD has measured. I'm guessing small case motor, steel swingarm and narrower rear wheel equals different offset. Strange about the 900ie though.

I will source new pins at the next tyre change. Where do you buy them?

[Speeddog]

I'm pretty sure the major control on the carrier is whether it's a 4.5" or 5.5" rim.

I got my pins from a dealer.
Those, the cush drives, wheel bearings, and shipping turned my bargain wheel into ~market value wheel. 
But it'll all be new, so that's nice.

[koko64]

Ive seen the TPO pins, beautiful, but $$
I thought I was so smart getting the whole carrier and pins for $40. Who wants to buy a cush drive for a 750 for $40? .

[Blue]

I suspected that the M900ie was going to be the '3rd' kind, as it's the one that has the oddball symmetrical front sprocket.
But it was the same as the ST2.

I don't know for certain, but I thought the odd ball front sprocket was due to the M900ie using the 748's transmission and output shaft, hence the different front sprocket to adapt to the dual swingarm instead of the single. 
Also, I've wondered if the M900ie sprocket would be useful in other Ducati swingarm and engine swaps?  I dunno, just a thought.

[Speeddog]

Perhaps it's due to the 748 transmission, but my Monster S4 has the same trans and uses the normal sprocket. 

I had an M900ie in for a chain and sprockets a while back.
I carefully measured, and the alignment was better with a normal sprocket.

[koko64]

I've passed that info onto my brother. Very useful.

[GK]

I've passed that info onto my brother. Very useful.

Yes he did. Thanks Speeddog. I'll save myself $20 next time I need a 14t front!

Cheers,

GK