Ball bearings, that is. How do you know when the bearings are kaput, and need replacement? Don't tell me "when they feel like there's sand in 'em."  How do you recognize the fact from engine run characteristics? Noise? Fuel consumption? Exhaust color? Inconsistencies? What?

On second thought, how do you know when a plain bearing engine needs to be fitted with a new bushing, case, or scrapped?  Steve

Steve,

I know I can hold the nose up and just move the prop back and forth. That usually tells me if there is a potential problem. But historically, if it seems flaky, I pull the engine apart and use a feeler gauge on the bearing. If it's out of spec, I replace it. Of course, this is if I can find the chart for the particular bearing to find out what the spec is. If not, I just replace it if it in anyway seems questionable. Usually, I got to the Bearing Shop in Tacoma. They can match about anything.

Ball bearings, that is. How do you know when the bearings are kaput, and need replacement? Don't tell me "when they feel like there's sand in 'em."  How do you recognize the fact from engine run characteristics? Noise? Fuel consumption? Exhaust color? Inconsistencies? What?

   On the very rare occasions I had bearing issues, it was the sound it made. The moderately famous example was when the rear bearing went over the hill on a practice flight in the first round of qualifying at the 2003 NATs. It had a low-frequency sound like a 60-cycle hum in a hi-fi system. Very loud. It still ran fine and I actually flew an official flight with it like that and wound up a very close second on the circle after David. Actually, the runs that particular day were the first where I got the engine fully sorted-out, I run it exactly the same way since then. Ted's did the same thing after the W/C the next year, pretty familiar sound and also still ran fine.

     Brett