Step 4

In case you have not yet already done, place the engine on the chassis according to the manual that comes with the car and check if the carburator link is placed correct. If not, change the angle of the carburator or the link. Also check if the clutch bell is adjusted correctly against the main gear. Not to much or to little play. Install the header and muffler. Install the fuel and pressure line. Then we start for the real work.

Fill the tank with fuel. Ordinary race fuel with 15% nitro and a minimum of 10% oil will do. No special break-in fuel is needed.

The pictures below explains the needles you usually find on model car carburators.
We try to bring you for each brand a separate picture.

	NOVA ROSSI-REX-TOP-R&B 2 needle versions
	SIRIO 2 needle versions
	CMB flatslide type I and II 2 needle versions
	CMB R4 3 needle version

There are as many ways to break in your engine as there are engines.
The reason for break in is to get the new parts with their tolerances matched.
Below you will find the links to suggested break in instructions from manufacturers and known drivers world wide are using.
Also TEAM TWF8 method is there with full description.

general long life engine break-in

Warm the coolinghead of the engine with a hairdryer or any other heat generating device to get the engine on a temperature of around 90 degrees Celsius.
Perform this warming up sequence after each time the engine has cooled down.

Press the engine against the starter wheel and choke the engine by closing the exhaust for about 4 seconds. This is to assure that the empty fuel line is filled with fuel. Now connect the glow-plug igniter and start the engine without opening the throttle. If the engine does not start, turn the stationary (idle) screw by 1/8 turn steps (clock-wise) until the engine fires up. Now if the engine is running at stationary (idle) speed OK, check if oil splashes and smoke are coming from the exhaust. If not! Open the bottom speed needle by 1/4 turn steps until it does. If it is running richer (the engine stalls with a rumbling sound) turn the idle speed screw clock-wise until the engine runs stationary (idles) OK. Again check if oil splashes and smoke are coming from the exhaust. Do not touch the high speed needle yet!

Now, let the engine run at stationary (idle) speed for 125cc. of fuel with the wheel spinning free from the ground.
It would be better for the engine if the engine temperature will be between the 90-100 degrees Celsius during first tank of fuel for break-in.
Check the temperature and if it stays cooler as 90 degrees Celsius block the cooling head with aluminum foil so it will become hotter.

Let the engine cool down first after each tank of fuel with the piston in its lowest position.

For the rest of the break-in period make sure the engine runs at working temp of 90-110 degrees Celsius.

Now first open the high speed needle 1 turn (counter-clock-wise). The next 125cc. of fuel try to run the engine at average speed on the track. If you open the throttle fully the engine should run rich, this means that it should sound as if it runs like a 4-stroke engine and is producing a rumbling sound and is smoking heavily. Do not yet, open the throttle fully for more then 2 seconds. If the engine is not running rich no smoke and no rumbling sound, open the high speed needle again by 1/2 turn steps (counter-clock-wise) until it does.
In all cases smoke should leave the exhaust when the throttle is opened.

After the second cool down close the bottom needle 1/4 turn clock-wise. Check if there are still oil splashes coming from the exhaust. If not, open it 3/8 turn anti clock-wise. Run the engine again for 3 x 125cc of fuel with cooldown in between. If you open the throttle full and the engine will not pick up rpm's but is tending to stall due to a rich fuel mixture, close the bottom screw by 1/8 turns steps turns (clock-wise) until it is picking up rpm's OK. Still check for the oil splashes and smoke from the exhaust.

During the rest of the break-in period of 3 x 125cc of fuel with cooldown in between, gradually close the high speed needle by 1/8 turns (clock-wise) so the 4-stroke sound is disappearing gradually for every 125cc. of fuel you use. Keep checking the temperature of the engine and smoke trails coming from the exhaust.

The last 3 x 125 cc. of fuel with cooldown is preserved for the ultimate tuning of the engine. If needed close the high speed needle so the engine runs at its 90/95% of its maximum rpm's. The bottom speed needle needs to be adjusted also. If the engine is running stationary (idle) for 10 seconds and the throttle is opened fully the engine should pick up rpm's without any rumble or hick up. If it tends to rumble close the bottom screw by 1/8 turns steps (clock-wise) until it picks-up OK. If it tends to hick up (grasping for air) then open the bottom speed needle by 1/4 turns steps (anti clock-wise) until it rumbles again. Then close the needle by 1/8 turns steps (clock-wise) until it picks up rpm's OK.

During brake in check the engine temperature for abnormalities

Total fuel used 1.25 Liter

Click here for more carburators and needle settings

TIPS TIPS TIPS TIPS TIPS TIPS TIPS TIPS TIPS TIPS TIPS TIPS TIPS TIPS TIPS TIPS TIPS

TIP 1 ! The break-in period is 80% the key for a good running engine and a long lifetime. Try to stay below all maximum settings of the engine performance. If you are just running your car for fun, then be sure that the engine is running always at a richer setting. 
Try to warm up the engine for 2 minutes minimum by running the car at medium speed (rpm's) before asking the maximum power from your engine.

TIP 2 ! When your engine was running fine before and it does not want to start, then this is the golden rule. Open the throttle fully. 
Start the engine without connecting a glowplug igniter for 3 seconds. Lift the car and then close the throttle. Now put the glow igniter on and the engine should start, easily. If not check for fuel, defective glow-plug or whatever. But do not touch the needles. Only minor changes (all within a 1/2 turn) could be needed if the external circumstances are changed. A good running engine, does not need frequent needle changing.

TIP 3 ! Always check the engine temperature frequently, by putting some spit on your finger and then on the cooling head. If it does not evaporate the engine temperature is below 100 °C. You may close the high speed needle a little if required. If it stays for 3 to 4 seconds the temperature is OK. If it evaporate direct, then open the high speed needle until the temperature goes down. An engine temperature system is a nice feature and can prevent premature engine failure due to overheating.

TIP 4 ! After using your engine these are the things to do:
Remove all fuel in the engine and carburator by taking off the fuel line and let the engine run until it stops. Then put some after run oil in the engine and run the motor for 3 seconds on the starter box so the oil is spread inside the engine well. This will prevent rust building up inside the engine if not used for a long period.

TIP 5 ! Use a good airfilter.