As I’ve said before in a previous post:
No, just in engines in general.
Turbo kart… fun (but crazy!) 
Noob question, but as a bicycle mechanic I dealt with this debate often. Can the bearing on a kart be disassembled? Meaning separate the balls from the races?
To my knowledge, no. The ball bearings are press fit into the bearing assembly. The full bearing can be inserted into & removed from the cassettes that mount to the chassis. Straightforward maintenance is to clean by shooting WD40 into the circumference groove & follow up with Tri Flow to oil it.
I’d love to see a sealed bearing with grease zerk fitting for kart applications, but it’s just not a thing.
I’ve never given ceramics a thought, not permitted.
A lot of the higher quality sealed cartridge bearings can be serviced. You pull off the seals clump the balls to one side and pivot the inner race 90 degrees. Then you can polish the balls and the races with jewelers rouge. On a bike you can feel the difference, feels similar to ceramics at a 10th the cost.
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Ceramic balls are 50% lighter than steel balls. They are almost perfectly smooth and exhibit vibration levels 2-7 times lower than conventional steel ball bearings. They run at significantly lower operating temperatures, and allow running speeds to increase compared to steel.
They are mandatory on certain applications, such a high speed machine tool spindles. My general experience is in a CAT40 spindle, once you get to 15,000 RPM, ceramics are used. Think 75mm bearing ID turning 15,000 RPM…so 4.5 times the bearing race speed as a kart axle. These also use closed and sealed lubrication re-circulation system, so the lubricant is carefully controlled. At those speeds, it is usually some sort of oil mist system.
They provide absolutely no advantage in any karting application.
Hasn’t been mentioned, but how resistant are ceramics to compression & deformation? How would they hold up to the kind of strains that are experienced in karting?
What strains? Karting loads are nothing compared to automotive use of similar sized bearings.
True, but I wasn’t referring to high load RPM friction wear. I’m asking about any potential kinematic physical loading due to axle flex or whatnot. Is it a factor, or not?
I would think they would have more benefit on crankshaft bearings. Slightly higher temps, 15,000 + RPM and significant loading at TDC and BDC. I have noticed many manufacturers going to roller bearings in place of ball bearings on these high stress areas. Perhaps its a point of wear that a roller bearing can be machined to a tighter tolerance than a ball.
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Worst load on the bearing are probably during a crash and the repair effort straightening axle while it’s in the kart. 
Smaller diameter might help reduce engine size.
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Thats not entirely true, loads on kart bearings is far different then say a car wheel bearing.
Karts punish bearings but in a much different way. That being said, I roll on traditional bearings not cermaic hybrids thr Hertzian contact stress of ceramic balls can really cause havoc. In the bottom end of a 2 stroke though, pretty sure I would run them just replace often.
Sidenote, I’d love to place some strain gauges on a kart sometime and do some data logging. Bearing carriers, seat struts etc.
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I was referring to the axle bearings. With three sets on a 50mm axle, they have an easy life compared to the smaller ones on my old sports car.
Engine is a whole different thing.
For sure. In a Kart there is no suspension to help absorb the blows of undulating pavement. In a kart, the axle feels everything the tires do.
On the other hand, wheel bearings in a full size car are not suspended either… They’re unsprung…
Some dirt oval racers swear by ceramic axle bearings… But sometimes it’s hard to disseminate the BS people throw… I’d imagine many drivers who spent $500 on axle bearings are probably not going to admit it didn’t do jack…