I put a Keihin on a 2008 200 Rev 3 and have just bought the idle mixture screw with flex attachment on the end from Splat Shop. Does something locate the knob that you turn with your fingers? It seems like there should be some kind of bracket.

On my 09 evo there is a small plastic piece that clips on a hose. This is the mount for the knob end of the flex line.

As Liviob says the first EVOs had a small plastic clip (which hooked onto the clutch pipe I think)& held the knob at the timing side of the bike.

Later EVOs did not have the flexible adjuster, as you can always reach the adjustment screw with a long bladed screwdriver.

On the Evos we had with the extension, we kept the knob at the clutch side as the bend is less severe than going right under the carb, and access to the knob is easier.

Just above the circular clutch cover, above the left top cover screw, there is a bit of the clutch casing which sticks up above the level of the engine casing behind -a bit of uneccessary material. We drilled a small hole through that part so that it could be used for a small plastic cable tie. The flexible mixture cable just comes from the carb at the exhaust side, forward along the top of the clutch casing and the cable tie goes around the smaller diameter part immediately behind the knurled knob. Result -easy to get at and operate!

Just remember to clip off the cable tie if you remove the carb!!!