9
Need help or have any questions? Email us at service@globalhobby.net
Engine Break-In
☛XTM .15 series engines are ABC engines. The cylinder
sleeve is tapered at the top, causing severe resistance when the
piston moves through the top of the stroke. This is normal. When
the engine heats up to operating temperature, this resistance will
decrease and the proper clearance will be achieved. The break-
in procedure will guide you through the steps necessary to prop-
erly break in your new XTM .15 series engine. Please follow
the steps closely.
☛The break-in process allows the engine parts to perfectly
fit to each other and properly protect each part from premature
wear. The engine should be broken in using a good quality R/C
car fuel that contains no more than 20% nitromethane.
❑Follow steps # 17 through # 22 in the Quick-Start Guide to
fill the fuel tank and to become familiar with the engine's start-
ing and shut down procedures.
❑Once the engine starts, keep the glow starter attached to
the glow plug and let the engine to run for about 1 minute with-
out giving it throttle. This will allow the engine to warm up. At
this point the engine should be running very “rich” and there
should be excessive white smoke coming from the exhaust pipe.
❑After the engine has been running for about 1 minute, re-
move the glow starter from the glow plug. Advance the throttle
in short, quick bursts and drive the truck around for about 2-3
minutes. If the engine is running rich enough, you should notice
excessive white smoke coming from the exhaust and the engine
should sound like it’s running very rough. Also, the truck will
barely be moving. If there is not excessive white smoke coming
from the exhaust, richen the high speed needle valve. After 2-3
minutes stop the engine by pinching the fuel line to the carbu-
retor (see Quick-Start Guide, step # 22).
❑Let the engine cool for approximately 10 minutes, then re-
startit. Setthehighspeedneedlevalve mixture to a slightly leaner
setting, about 1/8 turn more in. Repeat the step above then stop
the engine and let it cool for approximately 10 minutes.
❑Repeat the procedure in the step above, while leaning the
needle valve slightly more each time. In all, you should run the
engine a total of about 30 minutes. After 30 minutes of run-time
the engine will be broken in. Run the engine with the needle
valve set slightly rich, but lean enough to power the truck. At
this point the engine should hold a good setting on the high
speed needle valve and you can begin to fine tune the needle
valve settings to increase performance.
WARNING - Please Read Before Starting your Engine
If at any time the pull-start becomes very tight or difficult to pull - STOP! The engine has become flooded and the excess fuel must be
removed or damage to the pull-start and/or engine could occur. To remove the excess fuel from the engine follow the steps listed below:
❑Completely close the high speed needle valve (turn clockwise) until it bottoms out.
❑Remove the glow plug from the cylinder head.
❑With the top of the engine pointing away from you, pull the pull-start cord several times to clear the excess fuel from the engine.
❑Check to make sure the glow plug has not been fouled, then reinstall it.
❑Reset the high speed needle valve 2-1/2 turns out from bottom.
☛Itisoftheutmostimportancethat the engine never be leaned
out too much. When running the engine, you should always be
able to see a trail of white smoke coming from the exhaust pipe.
If you can’t, stop the engine immediately and richen the mix-
ture. You should also make sure there is plenty of air flowing
over the cylinder head to keep the engine from overheating.
Fine Tuning Your XTM Engine
After your engine has been broken-in, you can set the high and
low speed needle valves for optimum engine performance.
☛Be careful to never lean the engine out too much. Re-
member that the lubricants for your engine are suspended in
the fuel. If you lean out the fuel mixture too much you will
also be lowering the amount of lubricant entering your engine.
Less lubricant means more chance of your engine overheating
and possible engine failure.
Setting the High Speed Needle Valve
❑Start the engine and remove the glow starter from the glow
plug. Allow the engine to warm up for about 1 minute.
❑After the engine has warmed up, drive the car as you nor-
mally would. If the engine seems to be running rich, lean the
mixture screw about 1/16 of a turn at a time until the desired
setting is achieved. Always make sure you run the engine slightly
rich - you want to be able to see a white exhaust trail at all times.
❑To get more power from your engine you can use fuels
containing up to 30% nitromethane. We must caution you,
though, that once you run the engine with increased nitro you
may not get satisfactory results if you decide to go back to a
lower nitro content. Also, if you use fuels containing 30% nitro,
we highly suggest replacing the stock .01mm head gasket with a
thicker .02mm head gasket (available separately: P/N 148186)
to lower the compression ratio. If you don’t lower the compres-
sion ratio, overheating and erratic running will likely occur.
Setting the Low Speed Needle Valve
❑Start the engine and lean out the high speed needle valve
as per the previous steps. Close the throttle until the engine slows
down enough so that the clutch is disengaged and the wheels
don’t turn when the car is lifted from the ground. Allow the
engine to idle for about 10-15 seconds.
Continued on Next Page
