if you hunt around you can buy most small bearings in the region of C2, C3, C4 radial internal clearances (RIC) etc etc......it all depends upon how much you either crush the outer or inner races via interference fits, ultimately you want the resultant RIC to be "just" in the clearance situation, not too sloppy and deffo not tight, then you are sure the ball to race contact angles are nice and low in the region of 5 to 10 degrees......the trick is to minimise this crush distortion via using VERY close sliding or transition fits, personally the Honda style of crank to bearing fit is far too slack for my liking, but remember those engines were designed to run at 3000rpm all day long in a generator.......if you are looking for a really nice bearing solution you need to be looking at the ABEC grades, which is the overall quality and precision associated with the eccentricity (roundness) of the tracks in both races...... most commercial bearings are ABEC1, this is the minimum and still ok for all karting applications, for a very posh high-speed motorsport F1 / aerospace type bearings you should be in the region of ABEC3 to 5......if your building a satellite or dental drill that spins to 300,000rpm, then you need to be looking at the top of the range ABEC9, but you will be paying well over a grand per bearing!.....for this sort of level of detail really you need to deal direct with NSK, SKF, INA, NMB etc, as I normally find this is way over the head of most bearing retailers / middle-men.......anyway, best advice is keep your end float below 0.2mm and spend the big money on testing time!.....don't get sucked into the ceramic bearing fantasy, in reality all you are doing is paying for the high ABEC grade, the ceramic balls do nothing in any karting application.....we spin our electrical motor to 70,000rpm and we have an all steel bearing with 22mm OD, and it lives for several thousand hours, each bearing consumes about 10 watts at 70,000rpm, then consider 1 hp = 746Watts watts.....its hardly worth chasing for your average club racer
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