APRILIA RS 125 CHAIN SPROCKET INFORMATION ( WHATS BEST SIZE SPROCKET ) RS125

Aprilia RS125 workshop manual for sale Ebay UK 

Aprilia RS125 Sprocket & Gearing Guide

When tuning a 2-stroke RS125, the final drive ratio is the most cost-effective way to change the bike's character. Here is the technical breakdown:

• The Stock Baseline: The standard setup is typically 16/39 or 17/40 (Final Drive Ratio ~2.44).

• The "Acceleration" Setup (16/40 or 15/39): * Goal: Quicker off the line and easier power-band entry.

  • Effect: Reduces top speed but makes the bike much more responsive in city riding or tight "twisties."

• The "Top Speed" Setup (17/39 or 16/38): * Goal: Higher maximum velocity for long straights or tracks.

  • Effect: Slower acceleration; the engine may struggle to "pull" the taller gear if not fully de-restricted or if you have a passenger.

• Chain Selection: The author emphasizes that a 125cc 2-stroke puts high-frequency snap stress on a chain. Stick to DID Gold or Renthal 520-pitch chains. Avoid "unbranded" kits which stretch quickly and can snap, potentially damaging the engine casing.

Aprilia RS 125 

Sprockets:

The bigger your front sprocket is the faster the top end, the smaller it is the faster the acceleration .

The bigger on the back the quicker the acceleration the smaller  the better the top end.

The standard set up is 16/39

 39 tooth sprocket on the back , 16 on the front.

 Change the size of sprockets for more or less acceleration/top end.

Aprilia rs125 sprocket mph graph

If your getting new chain and sprockets get good quality , they cost a

 bit more but it is well worth it as usual you buy cheap you get cheap

 and with chains and sprockets you do not want any failures  best to

 stick with standard than change to cheap sprockets and chains .

see the sprocket calculator 

the Aprilia rs125 blog

a sprocket mph calculator 



sprocket calculator



I use DID gold chains as they are excellent and look great too .

Buy DID chain sprocket kits from Ebay UK here 

see more Aprilia RS 125 posts here 

BUY the ultimate Aprilia RS 125 workshop manual bundle HERE