RCU Forums - 1/8th Nitro Buggy Break In, Tuning, and Cleaning

Break in:
- Mark bottom dead center so you can always put your engine there when you shut it off. The easiest way to do this is to remove the glow plug and rest an object such as an antenna tube on top of the piston. Once you have done this, rotate the flywheel until the object is at its lowest point. Make a scratch on the flywheel that you can easily line up with some other part of the car to know the piston is at bottom dead center. This is done because the engine has a tapered sleeve (top is skinnier than the bottom). The sleeve’s taper acts as the seal for the engine, since the piston in these engines do not have ring seals. As the engine heats up the tapered portion expands and allows the piston to just barely fit through. By making sure that you put the piston at bottom dead center each and every time you turn the engine off, you keep the piston from being trapped in the tapered section, when the engine cools. If you leave the piston above BDC, then it does not allow the sleeve to contract fully, which causes premature wear.

The heat cycle method is probably the best method for proper engine break in. This involves getting your car up to running temperature for short bursts to allow the metals to be stressed in conditions similar to normal running conditions, as opposed to the overly rich conditions that engine manuals used to suggest for break in. First, prime your engine by covering the exhaust tip while trying to start the car, and watch to see that the fuel is sucked just to the opening of the carburetor. Then apply your glow ignitor and attempt to start the car. If the car does not start, and you are sure your ignitor is fully charged, try leaning the high speed needle 1/8th of a turn (clockwise) at a time until the car starts. Run your car until the chassis heats up. Adjust the mixture of the engine such that the car runs around 200-220 degrees (measured at glow plug), and a pinch of the fuel line causes the car to die in 5-7 seconds. Also, your idle should be as high as possible without engaging the clutch. Run your car for 2-3 minute intervals, and allow the engine to cool fully between cycles. To adjust your engine so that the temperature is warmer, you need to lean it out (less fuel, more air), by rotating the high speed needle about 1/12th a turn (1 hour on a clock) clockwise. To adjust it cooler, you need to richen the engine (more fuel, less air), by performing the opposite. To adjust how quickly the engine dies when you pinch the fuel line, you need to lean the low speed needle to make the engine die sooner, and richen the low speed needle to make the engine die later (same as above leaner = clockwise, richer = counter clockwise). Do not be afraid to get the engine above 200 degrees! Running it too cool can cause just as much damage as running it too hot. This is because an overly rich condition makes more fuel for the engine to compress, straining engine components.

Once you have run about 45 minutes worth (not counting cool down time) your engine is ready to be tuned for performance. Shoot for temperatures between 230-250, and a pinch of 3-5 seconds, again with the idle as high as possible. Both during break in, and afterwards, you should always see smoke from low to mid RPMs under acceleration.

Daily Tuning:
- Your engine will require re-tuning just about any time that the weather changes, if you change fuel or type of glow plug, as well as at the beginning of each day of driving. Simply follow the above guidelines after it is broken in, 230-250 degrees, 3-5 second pinch, and as high of idle as possible. Always restore the car to BDC after every time you shut it off. If you live in a humid environment, after run oil is a good idea if you won’t be running the car again for several days. Despite what people say, you do not simply put two drops inside the engine and call it done. The purpose of the oil is to keep water from collecting inside the engine from condensation. So it is best to thoroughly fill the engine with after run oil, which is really nothing other than Marvel Mystery oil, and occasionally MMo with a blend of automatic transmission fluid. Fill your engine up with this for storage.

Cleaning:
- The more often you clean your car, the easier it will be. It helps if you have access to an air compressor, but it is not required. For a quick cleaning, simply blast the car off with the air compressor, if it is just dusty (or wipe with a rag if no compressor is available). For a more in depth cleaning, remove your engine from the car, and use the two fuel lines to plug the open holes so dirt doesn’t enter the tank or the engine.. Run one fuel line from the tank’s fuel tap, to the tank’s pressure tap. Run the other fuel line from the carburetor to the exhaust pipe nipple. Once the engine is out of the car, remove the electronics. This is easiest done by taking off the two servo horns, and removing the radio tray. You don’t have to disconnect the servos from the receiver; you can simply wrap the radio tray/servos with a plastic bag and leave them attached to the car (by the servo wires). Once the engine and electronics are taken care of, get a spray bottle full of something such as a de-greaser (I use Simple Green) that is watered down. Spray the car everywhere, let it soak and then spray the degreaser/dirt/ooze off with the air compressor. By watering down the mixture, it runs off easier when you spray it with the air compressor. Use an old toothbrush to get to the hard to reach areas. Once the car is done, remove the air filter from the engine (still out of the car), place some plastic wrap around the carburetor opening and secure it with a rubber band. Now clean the engine in the same manner as the car described above. Then, clean your air filter thoroughly, even the smallest particles can cause problems for your engine. I soak it in gas, then use Simple Green, to wash out the gas, then use water to wash out the Simple Green. Then set the air filter somewhere clean to dry off. It is not bad to also run a pre-filter on top of your air filter, if you run in dusty conditions. A pre-filter is simply a foam outer layer that is slipped over the air filter. These can be picked up at just about any hobby store that stocks nitro r/c supplies.

While you have the car part way apart, it’s a good idea to check on the following and repair/replace anything necessary:
- All bearings rotate freely
- Diffs rotate freely
- Suspension is not binding (remove shocks and move suspension pieces by hand)
- Shocks do not feel mushy at the beginning of travel (check for leaking seals, if they do and rebuild if necessary)
- Clutch shoes are not worn down (if using aluminum shoes, file down any burrs on shoes to prolong shoe life)
- Tires are not coming unglued
- No parts have excessive play (repair, adjust, replace as necessary)

Once everything is inspected, you can either re-assemble the car, or first give the plastic pieces a shot with some WD-40. This will give it that new look again. Wipe off any excess when done.