Originally Posted by afm

There is absolutely no problem with the bottom end. With the proper setup this engine will drive away from any other engine from standing still. If your engine bogs and your carburation is right, then you are either running a clutch which engages too early, a pipe that does not suit the motor, or improper gear ratio.

You need your clutch to engage when the engine has reached it's optimal rpm range, which is higher in the case of the CRF engine. The CRF engine develops it's power later, meaning that the clutch has to engage roughly 5000rpm later. Obviously most clutches in their original form are not designed for this.

The stiffness of the spring and the gap between the clutch bell and the shoe are both important. Also remember that when you tighten a spring, the pressure increases exponentially. If you screw the spring adjust nut 2mm versus 1mm you will have a lot more than 2 times the pressure. By tightening a spring too much you reach a point where it does not fill it's spring function anymore so if you tighten a softer spring it's not the same as using a stiffer spring from the start.

The only one which gets quite close is the Kyosho clutch with these settings:

Kyosho White Clutch Weight - Drilled to 3.5mm
Kyosho 1.9mm Hard Spring at 1.40 setting
Gap = .50
Kyosho Grey Clutch Shoe

With these motors you really need to adjust the GEARING!!! Everyone remember, this engine likes to REV so be careful to not hand too much gear on it. Use a shorter gear ratio and the engine works much better!!!

Recommended gear ratio for most tracks is 7,38 en 1st speed and 5,09 in 2nd speed.

AFM