THE ALL NEW

CMB 91 RS LONG STROKE , BALL RACE BACK AND FRONT

Exhaust 181 Degrees. Transfers 120 Degrees. Boost 124 Degrees.

Disc Open 151 Degrees. Close 55 Degrees. all measurements approximate

I have run the RS91 this weekend straight out of the box. I did not even adjust the carburettor. The motor throttles perfectly and has good power. It gave good throttle through the whole range and the pipe was able to be shortened and I still was on my 5470 propeller. The motor has more torque with these timings and  top speed was equal to some of my old tuned motors.

Update If you shorten the pipe too much and go lean you will damage the piston (Detonation) I have added a .1 shim and the motor still goes ok with good speed and throttle

Bore 27.5 mm Stroke 25.2 mm