I have one of these engines NIB (#6550) from when I 1st started in this hobby. It sits in the engine drawer in my shed, unused and generally ignored. I did put some after run oil into it when I got it and on occasion, fit a prop to it to turn it over and spread the oil around inside.

This thread has got my interest in perhaps fitting it into a .46 sized sport model.

Summing up on the prop tests etc, An 11.5 x 7 or 12 x 6 Prop for general sports flying? (Not 3D)

Can anyone tell me how loud they are with the stock muffler? Noise is becoming an issue at the field I fly at and some of the older motors do not measure up. For example another guy flying a K & B .65 Sportster, removed the baffle from the stock exhaust and the motor failed a noise test. (Max 98 Db)

As a reference, engines such as my Super Tigre G.51, with the stock exhaust, come in around 93Db (as measured with the clubs equipment)