450 rear sprocket slop

[graeme]

Seeing how it’s been a bit quite here lately, a question.
Time to change sprocket and chain on 450 RT.
New 35 tooth rear sprocket measures 110.02mm ID.
Original sprocket carrier boss measures 109.59mm OD.
This allows close to .5mm slop that the 7mm bolts would have to cope with to hold the sprocket central.
I can’t see the bolts have any chance of doing this.
My thoughts are to shim the sprocket to the carrier with .25mm shim to help hold it central.
Your thoughts ?

Regards Graeme

[blethermaskite]

my experience with replacement/aftermarket rear sprockets (on any bike not just Ducati) has taught me to check every dimension before I fit, I find concentricity is often a problem and I have returned several in recent times (one was 1.75mm out of concentricity with the centre bore). I would try exactly the same method as you suggest to centralize the sprocket probably with a smear of epoxy adhesive on the shim to insure it doesn't escape in service.
Cheers,
George

[amartina75]

Are you concerned with concentricity or torque acting on the bolts? The torque on the bolts will be the same either way. If you are concerned with concentricity then you’d have to mount the sprocket on the carrier and indicate it in relative to the bearing bore. I would think a few thou TIR would be ok there as well given the bike it’s going on won’t be breaking any land speed records.
I would think Ducati held better tolerance than that but without seeing original drawings or measuring a bunch of parts I wouldn’t know. You could ask the manufacturer of the sprocket what their tolerance is, maybe it’s out of spec. If you haven’t used the sprocket yet then you could just return it.

Aaron

[graeme]

Hello George and Aaron,
I will check the sprocket outside in relation to the axle bearing as I have seen badly machined sprockets before (tight chain loose chain)
I planned to devcon shim to the sprocket ID to centralise it to the carrier.
There is no evidence the carrier boss has wear apart from slightly elongated holes from loose sprockets in the past.
Thanks for your thoughts

Graeme

[amartina75]

Graeme,

If you can setup the carrier between centers or on a straight shaft and indicate the sprocket in with the bolts not fully tightened. Then torque the bolts down, recheck runout, lay the assembly flat and fill the gap with epoxy.
For added piece of mind you could use new grade 8 bolts as well.

Aaron

[Jordan]

"You could ask the manufacturer of the sprocket what their tolerance is, maybe it’s out of spec."

Good luck with that.
It would be good to know who sells this junk.
There are too many reports of wonky sprockets.
Unlike some pattern parts, it's not easy to fix.

[graeme]

Hello Jordan

PBR

I’ve used them before and never noticed this
Perhaps I never looked

[Jordan]

Thanks Graeme,
Your loose sprocket fit is bad enough, but it's the badly non-concentric ones that really are inexcusable.
I think your idea to shim is good.

[linker48x]

You may be overthinking this. No reason to tolerate or correct low quality or asymmetrical parts. I have always gotten high quality American made custom sprockets for my race bikes, from several sources. Don’t know if they make one for you, I have never bought a custom Ducati sprocket, but for instance you might try https://sprocketspecialists.com/custom-builds/

[linker48x]

You may be overthinking this. No reason to tolerate or correct low quality or asymmetrical parts. I have always gotten high quality American made custom sprockets for my race bikes, from several sources. Don’t know if they make one for you, I have never bought a custom Ducati sprocket, but for instance you might try https://sprocketspecialists.com/custom-builds/

Oops, somehow repeated it. Anyway, Point is there are alternatives.