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790 Duke 2020
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175 Posts
The stock bike's air/fuel ratio is perilously lean to comply with exhaust emission laws. So whenever you fit a freer flowing exhaust system it will run even leaner, because the reduced back pressure will allow more unburnt fuel to escape via cam shaft timing overlap. Consequently you will get less power (remember it was sub-optimal to start with) and you will be in risk of making the valves and piston crowns even hotter, potentially risking a mechanical failure.
Freer flowing exhausts are only worthwhile if you also have the ECU remapped to suit.
 

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2021 KTM Duke 890R
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13 Posts
Me and my friend have the 21 duke r. Both have arrow slip on with db killer. He put mid pipe on his and his bike power went flat and much slower. We will do a roll on and from the drop i will pull away very quickly.

I just put the rapid bike system on the bike yesterday and it autotunes. In the mid range it has added about 10% fueling and thats in just 3 rides. And again thats with stock header, cat conv and slipon with db killer. As previously stated, very lean stock. Now bike is running much stronger.
 

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4 Posts
Me and my friend have the 21 duke r. Both have arrow slip on with db killer. He put mid pipe on his and his bike power went flat and much slower. We will do a roll on and from the drop i will pull away very quickly.

I just put the rapid bike system on the bike yesterday and it autotunes. In the mid range it has added about 10% fueling and thats in just 3 rides. And again thats with stock header, cat conv and slipon with db killer. As previously stated, very lean stock. Now bike is running much stronger.
Rapid bike evo system?
 
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