I also fly a 912ULS in a model 4 Kitfox.
I did not build it.
Does anyone have a photo to show the location of the broken bolt.
Thanks
I did find what broke that bolt. I had a vibration at 3000 rpm. I've been trying to chase it down. I cleaned the spark plugs, checked the floats, checked and cleaned out the mid range jets. while I was running it after all the carb work, which also included checking to make sure the clips were on the 3rd from the top. I noticed the spinner bouncing around big time at 3000 rpm. today I tore into it and got the spinner nice and centered to the prop. wow, nice and smooth now. hardly any vibration at the 3000.