Worn Out Motor

Eventually all good things must come to an end. This is also true when it come to your nitro motor's internals. Generally the area of concern, you first notice, is your piston and sleeve. A nitro motor, while similar to a gasoline motor in some aspects, doesn't have rings like a full-size car or truck would. Instead it relies on the fact that the sleeve is a slightly smaller diameter at the top than it is at the bottom. This provides a tight seal inside the combustion chamber when the piston reaches the extent of it's upward motion.

Over a period of several gallons of fuel, the piston and sleeve will start to wear. Once this happens the once tight seal starts to disappear. Eventually, due to this, the motor will show symptoms such as becoming hard to start, stalling frequently, and beginning to run hot all the time. When this occurs some parts of the motor will need to be serviced.

There are several different methods that can help you determine whether your motor needs to be rebuilt or not. One of the simplest is to simply try and spin the flywheel counterclockwise with your finger while the glow plug is installed. It should be very difficult to turn when the piston is near the top of the sleeve. This method is the easiest way to help determine if the piston and sleeve need to be replaced. It does require a little experience when determining if enough resistance is felt however.

Another option is to test your motor with a compression gauge. You can do this yourself, if you purchase a gauge, or you local hobby store can do it for you. The downside to this method is that there's no clear cut answer on what's a good or bad compression reading. Many factors such as the brand of gauge, temperature of the motor, and even the characteristics of the motor itself, can greatly affect the readings you obtain. To use this method, I would suggest obtaining a baseline reading while the motor is new. Make sure you also record the operating temperature as well. Then you'll have something to compare against later as the piston and sleeve start to wear.

The last method of checking your piston and sleeve isn't the quickest method, however it also doesn't require much experience nor previously recorded baselines. With this last method you simply remove the piston and sleeve from your truck and then push the piston into the sleeve to see how far it slides into it. When using this method, little effort should be used to slide the piston into the sleeve. As it reaches the top of the sleeve you may encounter some resistance. If it still continues to slide to the top of the sleeve or beyond with little effort, it should be replaced.

The pictures below show a piston that's slid into the sleeve. This picture shows you about where you should start encountering some resistance.

This picture shows you a piston and sleeve set that should be replaced. Notice how the piston can be slid beyond the top of the sleeve.

When the piston and sleeve are worn out you have several options. Obviously you can simply purchase a new motor. You can also replace just the piston and sleeve, although when going this route it would be wise to replace the connecting rod as well. The connecting rod is the vertical part that raises and lowers the piston in the motor. Due to the fact it can slightly stretch of time, replacing it along with the piston and sleeve would be the best course of action.

If you are using a Traxxas motor you can also opt to use their Engine Exchange Plan. Under this plan you send you motor and a payment to them, and they'll return a new motor back to you. It's a little cheaper way to get yourself a brand new motor. Since other components in the motor can fail over time as well, it's a good way to ensure your truck always has a fresh motor.