Mabuchi make a colossal variety of motors!
GM's nominal figure for a standard 'S can' is the accepted norm, though it should be born in mind that factory mass production tolerances will pemit +/- 10% on that figure of 18,000 rpm and the odd 'flier' can exceed even that range.
From testing Mabuchi S motors on my Kelvin Light test bench, the highest RPM I have seen is 21,500 at 12v after running in at 5v for 1/2 an hour. The average for new motors I have found to be 20,000. After a days racing these motors tend to lose between 500 and 1000 RPM. The T spec Mabuchis average 21,500 but hvae more torque, V spec average 23,000 with about the same torque as the T. the T and V spec OZrace motors tend to hold their performance better than the S spec from Fly and Hornby.
The specifications are there - look in the product listings and you will find them, or alternatively contact your local dealer or visit your dealer and look at the motors as often (not always, just often) they have the spec printed on the side of the motor.
Another problem rears it's ugly head though - some manufactureres quote a top RPM at 12v, others quote at 14.8v. Where does that leave us? Frankly, I am more likely to listen to someone like 250 GTO who has actually tested them and run them in properly than the labels on the units.
as with any motors on the market
you get good and bad
the best way i have found to test a motor to see if its a good high reving one is to use a multi meter.
set it to OHM's
the lower the ohms the more rmp
standard mabuchi comes in around 6 for a good 1
evo 2= 5 to 6 ohms
evo 3= 4 to 5
evo 4= 3 to 4.5
and so on
The short Fly Racing motors wtih the Blue wrapper usually rev to 24000 at 12v and around 29000 at 15v. These motors are very peaky with low torque and poor braking on low output transfomers. They perform better with a PSU giving at least 15v and 2amps.
Dr Sticky's method of testing is good as a guide if you want to check a motor before fitting it in a chassis and dont have access to a test bench.
Ohming the motor accurately requires disassembly and metering the wind directly. If you try to do it by touching the leads, you dont get repeatablity.
Timing: yes it is critical. Now, the way these things are built, there is about 2mm variance in the attachment of the com around a centerline, meaning anywhere from +/- 5deg, and THEN, the slop in the assembly of the brush mount itself adds in another variable of 5-7 degrees, again plus/minus.
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