Here's some interesting Mabuchi motor facts from another site/author, edits by me in <> and at the end --
"Mabuchi make (and made) many, many different versions of the 540 motor. Unfortunately since it is actually an industrial fractional hp dc motor, they are primarily classified by their output and consumption rather than the winds, which RC racers are more familiar with.
The coding schema used by Mabuchi is quite simple, and there are basically 3 types of motor that look very similar externally, and only their code number can identify them:
The RS-540SH series is the one typically used in RC car kits and this comes in 3 versions, the 5045, 8023 and the 6527 <I've also heard 5722>. Where the first 2 digits describe the wire diameter: 50 = .50mm etc and the last 2 digits the number or turns: 27 = 27T etc.
You will need to look at the motor label/number to know which you have, the RS-540SH-6527 being the typical one put into the Japanese RTR kits etc....... and is the 27T motor. They do other (and lower wind motors) but these were marketed under the "Dyna" name.
The can finish only designates the motors original intended market, matt tin plate finish for industrial use (tools etc) and nickel plated for toys, including RC cars.
You won't actually find the RS-540SH-6527 <or 5722, they only list the 5045> in the Mabuchi information though which does make it confusing!"
They also make an RS-540RH-5045 in the same can package as the RS-540SH-5045, but the RH motor is 2.5K-3K rpm (or about 1/3) faster than the SH at 6.0 - 7.2 volts!