How many miles are on the old chain? If the chain is fairly worn and you install just a new sprocket the chain will wear it down somewhat faster than if you replaced both front and rear sprockets and chain.

You can find kits that have all 3 for less than buying each component individually.

 

The complete chain set is fairly new.
Really wanna know if I can use the same chain lenght of the 47t for a 42 tooth for example.
I guess there's some sort of formula for that right?

 

There might be a formula but if you're going from a 47T to a 42T you could just install everything, move the chain adjusters to their shortest positions, wrap the chain around the sprockets and see if any links need to be removed.

Do you have a chain breaker/rivet tool?

 

True... I just wanted to make sure it fits before I go out buying a new sprocket 😁

Now I need to figure out if I'll go stock or go halfway...

 

If your using the same chain then it would need a few links cut off. You might be able to by another master link, but if your replacing one sprocket why not just replace both sprockets and the chain and do it right? Its really not that expensive if you already have the tools to do it.

 

True, but the set is still pretty new.
Picked up a 42T rear today, see how i like it....

Im trying not to cut the chain (at first) so i can try some different rears.

 

You can cut the chain by carefully grinding down the rivets from the link to be removed with an angle grinder, just go easy on it so you don`t fry the seals. But on bikes this powerful it`s heavily recommended to NOT use a clip style master link, I`ve succesfully riveted one chain with a small vice and a ball head hammer but it` s really up to you can you do it or let a shop take care of it for you and have peace with it and know it`s done right.

There are numerous different calculators for the sprockets in the net

https://www.rbracing-rsr.com/chainlength.html

REBEL GEARS CUSTOM MADE MOTORCYCLE SPROCKETS ANY SIZE

Gearing Commander: Motorcycle Speed, RPM, Chain & Sprockets Calculator

Here`s a few, took me a minute to google and link.

 

So took the rear wheel out, unbolted the sprocket, put the "new" one on, put the wheel back on, slid the chain on....

and...

previous owner put on a 520 kit instead of the oem 525

Mattson: thanks for the links!