Stock Motor Break-In Technique

Breaking in stock motors is something that is a personal thing to almost every racer. There are almost as many different ways to break in a new stock motor as there are racers that run them.

Applying 400 grit lapping compound to each of the bushings and running the motor on Turbo 30 at 2 volts. This allows the lapping compound to work. It is the way between the motor shaft and the bushing. As the motor spins with the lapping compound on the bushings, they become polished. Lapping compound is similar to Trinity's Bushing Buster. It is a paste that contains abrasive particles that work to polish the bushings as the motor spins.

The one needs to apply a small amount of compound on each bushing and run the motor until the paste turns black, then it needs to be sprayed off with motor spray. The process needs to be repeated four to five times. This repetition of process makes sure that the bushings are sufficiently polished. But if the same is done for longer span of time then the bushings will begin to show signs of end play as the abrasive in the paste begins to wear on them excessively.

After the last run with the compound, clean the motor thoroughly with motor spray to ensure that all of the lapping compound is removed from the motor. After the compound is applied properly choice of brushes for the motor is required. These brushes need to get them pre-seated with the brush contouring tool from RPM. After the brushes are contoured, switch the cutters to the serration tool and serrate the brushes so that they will break in quicker.

Generally speaking, a few runs around the track for practice should have them broken in. Normally, I just allow the brushes to break in during the dyno setup and then once I take the motor off the 'RACK' it is ready for use in the car.

It is important to note that brush hood alignment is vital to getting the most out of any stock motor. Ideally the brushes should be exactly 180 degrees apart and centered on the comm. There are several tools that exist to facilitate this

Other than this cleaning the motor is top priority when it comes to getting the most power out of a motor. It is also a good idea to have the comm cut after each day of racing if you want to continue to get maximum performance out of the motor.

Several people prefer to change brushes each time that the comm is cut. It is a bit much if one only removes .001 to .002 when cutting the comms on motors. If the brushes are fully seated and show no signs of overheating, leave them in until they become short or show signs of having gotten HOT. This is easy to determine. Brushes tend to have a blue tint to them where they come into contact with the comm. It is therefore suggested to replace them as the lubricant has been cooked out of them. Otherwise, it is preferable to get the moneys worth out of them and re-use them if they are still suitable.