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[jotjotde]

This post is about how I changed the front sprocket of my Ribelle. Most of this information was already posted somewhere, but it's hard to find, so I wanted to get all the relevant infos summarized in one go.

Looking at the number of teeth in front and the back, the front sprocket turn nearly three times more often than the back, so it is logically that it wears down much quicker.
In my case the sprocket was changed at 22,000 km and I did it now at 37,000 km because it already was visibly worn. It propably would have been good for another few thousand km, but then the chain would have been toast as well.

Sprocket Types
The originally mounted sprocket was a PBR 2078. For a Ribelle RS it needs to come with 15 teeth, for non-RS it's 16 teeth.
Alternatives are AFAM 61801 and JT Sprockets JTF704.
This time I chose a rubber cushioned one made by Esjot, a German manufacturer, but a similar one is apparently offered by JT as well.
Those sprockets are the same for a Aprilia 1100 Tuono, in case you want to look for yourself. Cost are about 20 - 40 €.

What To Buy
I decided to renew everything and bought the stuff via ebay.
The sprocket is fixed with a special shaft nut made by Swedish company SKM. The type is a KM5. Cost were 9 €.
A star-shaped locking washer is fixing the nut. The manufacturer recommends to change this every time together with the sprocket. Cost were around 1 €.
For installation, you need a special nut. I got mine for 17 €.

What Else You Should Know
I will spare you the gruesome details. All in all it took me 2 hours including cleaning (good opportunity to remove all the greasy dirt from that place) and re-aligning the chain after the job is done. The latter was necessary because the old sprocket was already worn.
I did not took out the back wheel, just drew out the axle after getting the brake caliper to the side. When the chain adjustor blocks are removed, the wheel can be pushed forward enough to allow the chain to be loose enough that the sprocket can be got out.
For removing and reinstalling the shaft nut I blocked the wheel with a 50 mm diameter steel pipe which I had cladded with duct tape to protect the paint on the wheel from being scratched.
Note that the shaft nut is asymmetrical. The chamfered side must point to the gear side.

Tightening torque for the shaft nut is a whopping 190 Nm. As far as I know, the same as for a Panigale V4.

So better be prepared! Take care that the bike is well fixed. If you are a 60 kg person you might better look for an additional lever for the torque wrench. You maybe are better off if an additional person holds the bike while you apply that torque.
Energica recommends to use green Locktite (high strength) for installation. Interestingly I found no traces of it when I removed the old screw. Nevertheless I used it now.
After tightening the nut, look which one of the 'wings' of the star-shaped locking washer is suited to be bend into one of the four grooves of the KM5 nut and bend it down into it using a small screwdriver and some light tapping with a hammer.

The Result
Now I have a brand new rubber cushioned front sprocket. Is there any difference to a normal sprocket? No.
The noise from the chain on the sprocket even got a tiny bit louder. That might be due to the fact that the chain is already 5,000 km 'old'. I will give it some time to 'settle', otherwise I will change the chain as well.
In the future I will probably renew the sprocket each time together with the chain.

[Pard]

Excellent writeup!

[Specter]

Quick note:
If you use cheater bars or anything like that on a torque wrench, you change the dynamics and it's reading is no longer accurate.  This goes for using extenders, universal heads or anything of that nature  when using a torque wrench on anything.  Just a friendly reminder.

Aaron

[Pard]

Excellent point!

[szczur333]

what about rear sprocket type?

[SBK74]

Rear is the AFAM 92630 (is stampted in the sprocket). I mounted a black Sitta sprocket, which IMHO looks much nicer:

https://www.wrs.it/en/rear-sprocket-and-pinion/121684-sitta-sprocket-step-525-for-rims-marchesini-oz-racing-rotobox.html

[jotjotde]

Thanks @SBK for pointing that supplier out.

Another alternative for the AFAM could be Superlite RSX SKU#92630RX (US-supplier) or from Supersprox (UK-supplier) who offer even custom-made stuff.
You need a sprocket for 525 chains, 44 teeth (for Ribelle), inner hole Ø76mm, bolt circle Ø100mm and 5 bolt holes Ø10.5mm.
I ordered a red-colored rear sprocket from them, but manufacturing time will be about 3-4 months (!).

[jotjotde]

Sorry for dragging this old post up, but I think it's good to add the following info.

After waiting additional 4 weeks (4 months in total) for the customized Supersprox rear sprocket, I found, after mounting, that it is not 100 % accurately manufactured.
It surely looks fine, but there is a tiny warp which makes a noise with every turn of the wheel which faded a bit after 2000 km of use.
It might go away completely after some more km, but I still think for the whopping price I paid this is unacceptable. So I cannot recommend them.


Cross-referencing:
For more info about rear sprockets refer to the following post.
https://www.electricmotorcycleforum.com/boards/index.php?PHPSESSID=619261556c253cd529f873807bbcf6b0&topic=13442.0

[coolhand]

Just changed the sprockets and chain on my SS9 (same parts as the Ribelle.

The fixing nut on the front sprocket, I should need to change it next time. Do you remember where you bought it, or the specs for it ? My dealer is not able to get a new one, so I plan to get a new one myself, good time in advance.

[smithy]

Just changed the sprockets and chain on my SS9 (same parts as the Ribelle.

The fixing nut on the front sprocket, I should need to change it next time. Do you remember where you bought it, or the specs for it ? My dealer is not able to get a new one, so I plan to get a new one myself, good time in advance.

Don't bother with the silly slotted nut, just use a normal hex nut, the rear axle lock nut should fit, (Same on the Experia too)....this does away with the need for the KM-5 socket and you can just use a normal 32mm socket.

I bought a few hex nuts with the correct thread size off fleabay, they work fine.

Smithy.

[jotjotde]

The nut for the front sprocket is a locking nut 'KM5', the original one was made by Swedish SKF.
Go and Google it, that should give you plenty of sources. Price is about 10-15 USD.
https://us.misumi-ec.com/vona2/detail/221006488483/?HissuCode=KM5&srsltid=AfmBOooek0NrNL3ZRgErCu6qvZsSR8uF7WbuLmg-14_jgiam-NngsZ8n

Don't forget to order a new locking washer as well, that is a 3 USD piece that ensures the nut becomes loose while riding.

So yes, I strongly advise to use a locking nut on the front sprocket. Just a hex screw is an invite for desaster. The bike can produce up to 200 Nm of torque and some substantial part of that is working in reverse direction e.g. if going from high speed into full recuperation.

[coolhand]

Thanx

Parts ordered!

Cheers!

The nut for the front sprocket is a locking nut 'KM5', the original one was made by Swedish SKF.
Go and Google it, that should give you plenty of sources. Price is about 10-15 USD.
https://us.misumi-ec.com/vona2/detail/221006488483/?HissuCode=KM5&srsltid=AfmBOooek0NrNL3ZRgErCu6qvZsSR8uF7WbuLmg-14_jgiam-NngsZ8n

Don't forget to order a new locking washer as well, that is a 3 USD piece that ensures the nut becomes loose while riding.

So yes, I strongly advise to use a locking nut on the front sprocket. Just a hex screw is an invite for desaster. The bike can produce up to 200 Nm of torque and some substantial part of that is working in reverse direction e.g. if going from high speed into full recuperation.

[smithy]

The nut for the front sprocket is a locking nut 'KM5', the original one was made by Swedish SKF.
Go and Google it, that should give you plenty of sources. Price is about 10-15 USD.
https://us.misumi-ec.com/vona2/detail/221006488483/?HissuCode=KM5&srsltid=AfmBOooek0NrNL3ZRgErCu6qvZsSR8uF7WbuLmg-14_jgiam-NngsZ8n

Don't forget to order a new locking washer as well, that is a 3 USD piece that ensures the nut becomes loose while riding.

So yes, I strongly advise to use a locking nut on the front sprocket. Just a hex screw is an invite for desaster. The bike can produce up to 200 Nm of torque and some substantial part of that is working in reverse direction e.g. if going from high speed into full recuperation.

Have done over 4000km since I swapped out the KM5 nut for a normal 32mm hex nut, no issues so far and it is holding torque with no indication of coming loose....done up to 190nm too.

Smithy.

[jotjotde]

Have done over 4000km since I swapped out the KM5 nut for a normal 32mm hex nut, no issues so far and it is holding torque with no indication of coming loose....done up to 190nm too.

Smithy.

I do not doubt what you say and I agree that these 4-grooved KM5 nut is a pain in the neck to handle.
But if and how quickly your hex nut becomes loose depends on several factors e.g. your riding style.
In my view this nut lock washer for the KM5 nut makes a lot of sense and I would always advise to install it. Having safety and not needing it is better than vice versa.

[jotjotde]

Sorry for dragging that old one up again.
But the safety for my fellow riders is a main concern for me.

Below you can find pics attached from my front sprocket when installed new at 65,000 km. As you see, I did not quite manage to turn the KM5 nut enough for a safety 'star' arm to fully fit into the groove. I really tried, but the 190 Nm are no fun and I had no nerve nor power enough to try 191 Nm.

The second pic is the sprocket at 81,000 km. You can easily see how the sprocket has wedged itself into the star arm, despite the 190 Nm torque of the nut.

For me that is a clear sign that a safety washer is an absolute must when installing the sprocket nut, whatever kind you like to use. Those washers are available also for hex nuts and they are just a few dollars. These dollars safe lives!