Basic Nitro Engine Break-in Method:
Breaking in a Nitro motor is always a bit of a challenge!
Don't get discouraged. (Read this entire article before continuing).
Get a friend to help.
You can take the pressure line off the pipe that goes to
the fuel tank and blow in there. This will force the fuel into the carb, very
Place the car on a block so the wheels are not touching
Heat the engine up with a heat gun or hair dryer. Try to
get it to 200 to 230 deg. F. This will make it way easier to start and put way
less stress on the con rod bushing and crank pin inside the motor. This will
make the motor last much longer as well.
Use the pull start (or even belter a starter box). Do not
pull the pull starter cord to the end of its travel ever, if possible, this
will damage it. Use your friend to hold the radio and give it a bit of throttle
once it goes. Use very little throttle or it will flood out, just enough to get
the rpm's up. Leave the glow igniter in place for this tank as you may find the
engine stalls if you remove it. This is normal. If it doesn't need to be on
then remove it.
The key next is to keep the temp up to 200 to 230 F. Temp
the engine on the side at the bottom on the engine case. Use the heat gun or
hair dryer to keep the temp up. Just be careful not to hold it in the same
location for too long.
Once the engine is running you may need to adjust the
trim on the radio to give the throttle a bit of extra gas beyond just the idle
setting. You should set the RPM so that the wheels are on the verge of turning
for the first 3 tanks of nitro. This will take a couple of hours. Let the
engine cool to room temp between tanks.
By the third tank you will probably have the engine
running steady without much interference from you to keep it going. You will
also notice a large amount of oil building up on everything from it spewing
from the stinger on the exhaust. This is normal and you can dump the hot oil
out from time to time to keep it clear. There should be quite a bit of smoke as
On the forth tank you should be able to place the car on
the ground off the 2x4 or block it has run on until now. The engine will also
be holding its temp a bit belter without the aid of the heat gun as much. You
can also lean the main needle a bit by now as well, possibly about 1/4 to 1/3
of a turn in (in is leaner).
Once the engine is running ok, place the car on the
ground and give it a bit of gas to get it moving, not much more than 1/8th to
1/4 throttle max. Avoid letting it run at to high an RPM at this point. Drive
the car gently away from you and then return it to your feet. You can repeat
this over and over again until the tank is done. I drive the car in swooping S
turns away then back and as the car turns in I modulate the throttle from idle
to about 1/4 throttle and then back to ideal again as I make the next swoop.
This is a very good thing to do for the engine as it will now start getting
used to running at different RPM.
As all this is going on stop once and awhile and measure
the temp at the glow plug or on the side of the engine case. Try to keep it at
200 to 230 deg, F. This may require you to block off the cooling head a bit
with some cardboard and even an old sock. This will allow the engine to keep
its temp. Keep adjusting the covering to keep the temperature correct.
Each tank of running will allow you to lean the main
needle a small amount. I would also increase a little bit how hard you give the
throttle for each tank as well. You will start to notice the engine is getting
freer revving on each tank through it as well. This is a sign that your break-in
is working. (I know it's a lot of work). You will learn a bit about how you
engine reacts to needle settings as you do this as well.
I will not cover how to tune your engine here as this is
another topic all together, however related it is. But after 8 to 10 tanks or
on some motors even more your engine will be mostly brocken in. At this point
its time to hit the track and getting a feel how to get a good race tune on it.
Just remember to monitor the temperature regularly as well as ensuring that
there is always good smoke coming out of the pipe. No smoke, no good, too lean.
Same goes with the temperature. Too hot is too lean. Thatís all I am going to
say about the tuning aspect right now.
Have fun with your nitro engine break-ins and remember if
you have patience and do a good job, this will result in a more constant
running engine, more performance as well as it will last much longer.