2): Locked motors: Obviously these motors are harder to clean, as you cant strip them down. This means it is very important to keep it as clean as possible, as often as possible. If you let the dirt build up too much, motor spray wont shift all of it.
For racing however things are very different! If you go by the manufacurers info, you will want to change the brushes every 3, yes, 3 runs!!! and get the com skimmed every 6 or 7 runs. From my experience at the southampton racing club, getting a skim really does make a difference! And replacing the brushes at the same time, will make your car feel ballistic if your motor is a couple of meetings or more old.
Now comes the nitty gritty. Do you you really need a com lathe? Well the first thing you will notice when looking for a com lathe, is how expensive they are! The cheapest new ones I have seen are around the �120 mark going up to a few hundred quid for an automatic one!
If you are not racing, then I would definitely say you dont need one. If your motor is losing power, get someone else to give it a re-build. There are plenty of racing shops around that offer a full re-build (com skim/new brushes/re-balance armature) for around �7.
Even if you are racing, you still dont REALLY need a com lathe, as there will allways be someone track side who wont mind skimming your com for a couple of quid.
If you want to get really serious about your racing, then get one, having one your self guarrantees all your motors will be in great shape all the time.
