One important thing to remember when breaking in a new engine, it will appear to not run correctly. It will stall, operate very inconsistently, and may even foul glow plugs. Don't get frustrated with it. Just keep working with it and it will become a smooth running engine. These experiences are what can be called "break-in pains". Every new engine has to go through this. When you get the engine started, be sure to keep it running by giving it throttle when it sounds like it's going to stall. Pulling the throttle quickly can also stall the engine. After a couple of tanks your patience will pay off with a very strong, reliable running engine.
Break-in should be done using at least 4-5 tanks of fuel. Please don't take short cuts and run less tanks. Don't listen to your friends that tell you that it doesn't really matter, IT DOES!
Its best to break-in the engine using the same nitro content as you plan to use for everyday use. The engine should be broken-in on a smooth hard surface. For a boat engines, try to find smooth clam water. Try to avoid breaking-in the engine on very hot, or humid days.
Turning the mixture screws clockwise will "lean" the air/fuel mixture. This will increase power and increase engine temperature. Turning the screws to the left counter-clockwise will "richen" the air/fuel mixture. This will cool the engine and make it last longer. When adjusting the idle screw, turning to the left will lower the idle and right will raise the idle. Remember to open the carburetor a little whenever you tighten the idle screw to prevent breaking off the tip of the screw.
Always break-in your engine without the body on the car, you want as much airflow as you can get to keep the engine cool. Do not run the engine too lean or you will over heat it and cause permanent damage to the internal components of the engine.
It is normal for the engine to consume a lot of fuel during break-in. This is because you are running it "richer" than you normally would to keep the engine cool and to flush out the engine as the parts "seat" themselves. Because of the richer than normal setting the performance of the engine will be limited. After break-in, you will then lean it out to gain performance.
It's always a good idea to get an extra glow plug (short, cold plug). It is
normal to have to replace it after break-in because of the deposits left on in
from the break-in process. Glow plugs are a normal item that needs replacing.
Because they have such a huge influence on they way your engine runs it best to
always have a few spares on hand.
Start your engine, drive the car slowly
around to let the engine heat up. Ease the throttle on and off slowly. Don't let
the car stay still for long periods of time, this will heat up the clutch bell
and could damage it.
The idle speed should be set as low as possible to keep
the engine running when the car is stopped.
The final settings on the top
end needle will vary slightly from engine to engine. Look for the following
performance signs:
Engine should accelerate quickly.
Blue/white smoke
coming from the exhaust pipe. If no blue smoke it coming out, you need to
"richen" the top end needle.
Alternate driving at low to medium speeds, with
short periods of high speed running
When the engine reaches normal running
temperature, it will pick up speed and performance will improve.
When the
tank is close to running out bring in the car and shut off the engine. Let it
cool completely, then refuel and run again. Part of the break-in process is also
to heat cycle the parts in side the engine.
Remember always run the engine
with a clean air filter.