<<...who knows what the balance is...>>

Good point. I confess this is one area where I'm a bit lazy.


I will spend hours balancing fans, fan hubs, rotor heads, etc., on a helicopter. But I just don't bother with most prop spinners anymore. The reason is I never noticed any difference one way or another.

I still do it on a large engine, such as my Laser 150; or a metal spinner of any size. There's enough mass there to cause a problem if the balance is bad out. But the smaller (less than 1.00 displacement) engines using a plastic spinner get the TLAR method; IOW, smooth up the slots as close as possible to each other with the Dremel, and bolt that puppy on.

Some may disagree with that; okay. But the three pictures above show four stroke engine/plastic spinner combos that were done that way, are well-used, and have zero problems. A fourth installation not shown is a 48 surpass on an LT-40. All of these engines are started by slapping the prop clockwise with a chicken stick.

I'm one of the most meticulous persons I know. But sometimes, a bit of sloth is okay....