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Replacing front sprocket

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I am looking at placing a smaller sprocket on the front of my St4S. Has anyone else done this themselves? I am mechanically inclined and dont think it should be to bad. What is the difficulty level in doing this? Does it take any special tools? Does anyone have any helpful hints? Thanks!
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I don't have my bike in front of me, but it was very easy and straight-forward on my ST2. I needed an allen wrench for the 4 (?) sprocket cover bolts and another wrench for the two bolts on the sprocket retainer. I did run into an issue with my stock 15-tooth sprocket and the chain hitting my clutch slave cylinder. I couldn't squeeze it out from under it no matter what I did, so I removed the three bolts on the clutch slave, dropped the slave to the side of the bike, and then just pulled the chain and sprocket off the shaft, then rolled the sprocket out of the chain. Installation of the new sprocket was the opposite, as I put the new sprocket on the shaft with it already cradled in the chain. I don't recall if I had the stock clutch slave or the Evoluzione on the bike at the time. Basically, the job only required two wrenches.

Edit - I believe I used some blue Lock-tite on the two bolts that go into the sprocket to prevent them from working loose and letting the sprocket "walk" on the shaft.
 

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Yep. What Desmo Demon said.
You definitely have to remove the clutch slave. Mine is stock.

You'll like the change.

But, for the record. I plan to put the 15 back on and go with a larger rear sprocket come time to change the chain and/or sprocket.
 

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Desmo_Demon said:
I don't have my bike in front of me, but it was very easy and straight-forward on my ST2. I needed an allen wrench for the 4 (?) sprocket cover bolts and another wrench for the two bolts on the sprocket retainer. I did run into an issue with my stock 15-tooth sprocket and the chain hitting my clutch slave cylinder. I couldn't squeeze it out from under it no matter what I did, so I removed the three bolts on the clutch slave, dropped the slave to the side of the bike, and then just pulled the chain and sprocket off the shaft, then rolled the sprocket out of the chain. Installation of the new sprocket was the opposite, as I put the new sprocket on the shaft with it already cradled in the chain. I don't recall if I had the stock clutch slave or the Evoluzione on the bike at the time. Basically, the job only required two wrenches.

Edit - I believe I used some blue Lock-tite on the two bolts that go into the sprocket to prevent them from working loose and letting the sprocket "walk" on the shaft.

My ST3 has one large (22 or 24mm i'm guessing) bolt holding the front sprocket on the spline.

Questions:

1. is this bolt a regular thread or "left handed"?
2. torque spec?
3. any tips or tricks here...I'm assuming I'll need to engage the rear brake to keep the engine from turning over.

Thanks.
 

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however you change the front sprocket be it by yourself or a mechanic,do it.i've just had my 2004 st4s in for its annual service and i got a 14tooth sprocket fitted and its transformed the bike.it pulls stronger and cleaner, hardly any juddering low down-feels like a 996cc bike should! GET IT SWAPPED
 

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I have one if you would like it, cover the shipping and I'll send it to you.
pm me

Mine had the 14 swap done when I picked it up.
I've since went to a 520did 15/42 (=2.80 ratio). 14/38 (=2.71 ratio)
stock 15/38 (=2.53)
My concern was with the raised rear ride height the 14 would wear the front
of the swinging arm, which it had worn the guide down a bit.
 

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Does anyone know the torque spec on this bolt?...i.e., the one securing the front sprocket.

Thanks.
 

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Fly said:
Does anyone know the torque spec on this bolt?...i.e., the one securing the front sprocket.

Thanks.
Fly -
Can't answer your ? about the torque spec. I might be able to help with that next week when I pick up the manuals for my '05 ST3. I do know that the big nut on the front sprocket shaft is bigger than a 24mm. A 30mm is a too small, but a 1 and 1/4" SAE fits, so it's probably a 31 or a 32.
Bill W.
 

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Fly said:
Does anyone know the torque spec on this bolt?...i.e., the one securing the front sprocket.

Thanks.
For what it's worth, the spec is 183 (or 186...I can't remember which) Newton-Meters.
 

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Not to hijack this thread, BUT....can the stock chain be used on an '03 ST4s if you go to a 42t rear, leaving the stock 15t front? Stock is 15/38, correct? Is stock chain a 525? sorry, I haven't picked up the bike yet...just preparing.
 

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Badger_WI said:
You can install a 40t rear sprocket with the original chain, but to go any larger than that requires a new chain.
Until I need a chain, that's what I'll do....thanks. I'm being frugal so I can justify the headlight mod, but more grunt down low is definitely a higher priority.
 

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I put on a 14/42 combo on the 03 ST4s and used the stock chain. It is not that it will not fit, its that many want to retain the stock wheelbase value. I dont feel the difference. When the chain wears and its adjusted, the stock WB will be changed to slightly longer anyway.
 

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ST4Rick said:
Not to hijack this thread, BUT....can the stock chain be used on an '03 ST4s if you go to a 42t rear, leaving the stock 15t front? Stock is 15/38, correct? Is stock chain a 525? sorry, I haven't picked up the bike yet...just preparing.

A 42T rear sprocket requires two additional links. My chain was fairly new, so Ducati Seattle just added the two new links to the OEM chain.
 
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