hi,
ronmar, you are right with the muffler pipe, is really heavy, I will fit a support to grab it with the frame. The engine is really running smooth, the knock may be by the side wall reflection, you know, a resonance efect.
Brialin, the fan is a standard electric car engine fan, was taken from a Dahiatsu 1/2 Ton gas pickup, is 12 volts DC, I used the generator power throw a 300 Watts 120/12 volts AC transformer, after rectified with a full wave diode bridge (the standard square four leg diode bridge). Icontrolled the fan with a timer, 5 minutes after start the engine (to allow warm it up).
PS: what about the two models in the video (the domestics hens)?