17x8 Xoar ; 89/90dB at 7m
20x8 Just Engines wood ; 86dB at 7m
Update
Ended up using the 20x8 wood JE prop. We blocked off the nearest stub to the exhaust opening. I had put silicon tubing over the stubs earlier.
Re-ran the noise test and this time it came in at 83.5 dB at 7 meters. Result!! Pass YES
So later on I will make up something to tidy it up and block it up altogether. Aluminium plug perhaps.
Max revs were 6450rpm with the 20x8 above. Hope this helps.
Also getting used to starting it. It needs the choke fully closed throttle fully open and turned over 8-10 times, then shut throttle and turn over again. Open choke fully and shut throttle and put it on fast idle setting. Turn ignition on , flick it hard over by hand and it should fire up after 4/5 flicks.
Still on 20:1 run in fuel and ever-so slightly rich
The muffler is baffled. The pipes go right up to the top of the canister. The pipes have holes drilled on four sides.