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Troubleshooting guide
Problem
Possible Cause
Solution
Vehicle doesn’t operate
Battery not charged or plugged in
charge battery/plug in
Receiver switch not “On”
Turn on receiver switch
Transmitter not “On” or low batteries
Turn on/replace batteries
Motor runs but rear wheels
don’t move
Pinion not meshing with spur gear
Adjust pinion/spur mesh
Pinion spinning on motor shaft
Replace pinion gear on motor
Slipper too loose
check & adjust slipper
Transmission gears stripped
Replace transmission gears
check and replace drive pin
Steering doesn’t work
Servo plug not in receiver
check if plug in/in all the way
Servo gears or motor damaged
Replace or repair servo
Won’t turn in one direction
Servo gears damaged
Replace servo
Motor doesn’t run
Motor plugs loose
Plug in completely
Motor wire broken
Repair or replace as needed
ESc damaged
contact Horizon Hobby Product Support
ESc gets hot
Motor over-geared
Use smaller pinion on motor
Driveline bound up
check wheels, suspension, and transmission
for binding
Poor run time and/or sluggish
acceleration
NiMH pack not fully charged
Recharge battery
charger not allowing full charge
Try another charger
Slipper slipping too much
check/adjust slipper
Motor worn out
Replace motor
Driveline bound up
check wheels, transmission for binding
Poor range and/or glitching
Transmitter batteries low
check and replace
Transmitter antenna loose
check and tighten
Vehicle battery low
Recharge or replace
Loose plugs or wires
check motor and power plugs
Slipper won’t adjust
Drive pin missing in shaft
Replace drive pin
Spur gear face worn out
Replace spur gear and adjust slipper
Chassis Tuning
The following are simple adjustments and easily maintained settings to assure proper operation and
performance. It is advised when making any adjustment that you do so in small increments and always
check for other parts of the chassis that are affected.
Slipper Adjustments
The Mini-Rock crawler is equipped with a slipper device offering both traction control and protection
for the transmission. The slipper is primarily used to help absorb sudden impacts on the drivetrain or
when using more powerful aftermarket motors and/or battery packs. Additionally, it can be used to
smooth out the flow of power to the wheels. Adjustment is made by turning the 3mm adjustment nut
clockwise (to the right) to reduce the slip, or counterclockwise (to the left) to increase the slip. As you
punch the throttle, the slipper should slip no more than an inch as it accelerates. With the included
motor and battery pack it should slip just a little. Make sure you replace the gear cover before running.
INCREASE SlIP
dECREASE SlIP
Steering Rate
Your transmitter is equipped with a steering rate control to the left of the steering wheel. This advanced feature, usually found only on competition-type
radios, allows you to adjust the amount the front tires move when you turn the steering wheel.
Steering Servo Saver Removal
The Mini-Rock crawler steering servo comes with a servo saver installed. As your rock crawling skills improve, we have included a steering arm that
eliminates the servo saver. Although this setup provides more precise steering, it does put your servo gears at risk for breakage. Use caution when the
steering servo is under severe loads.
Full Rate
Less Rate
1. center servo saver arm
2. Remove servo saver arm assembly from
the servo. Remove the steering ball stud
and install into solid servo arm.
3. With servo output shaft still centered,
install solid servo arm with the shorter
screw supplied and attach steering linkage.
Changing the Pinion gear/gear Ratio
Before you change the pinion gear, ask yourself why you are doing it. In general, if you change to a larger pinion, the wheel speed will increase but you will
see less acceleration and run time. This would only be advisable for low traction climbs. changing to a smaller pinion will give you quicker acceleration and
possibly a bit longer run time but a little less wheel speed. This would be good for high traction rock climbs. The pinion on the Mini-Rock crawler offers the
best balance of both. To change the pinion, remove the gear cover, loosen the motor screws and slide the motor back. Use the included 1.5mm allen wrench
to loosen the pinion setscrew. Place the new pinion on the end of the motor shaft and, using the flat of the pliers or a similar flat tool, push it on to the same
position as the one removed. See Setting the Gear Mesh below. Your Mini-Rock crawler comes equipped with a 14-tooth pinion, which provides an overall
ratio of 86:1. If you increase the pinion size to a 15-tooth gear, the ratio will change to 80:1 To decrease the pinion size to a 13-tooth will be 92:1.
NOTICE:
When running aftermarket motors, check with the motor manufacturer for correct gearing. Never over-gear the motor as it can cause overheating,
damaging it and the speed control.
Setting the gear mesh
The motor screws should be slightly loose. Slide the motor forward allowing the pinion gear to mesh with the spur gear. Snug
(not tight) the bottom motor screw and try rocking the spur back and forth. There is a slight bit of movement before the motor
is forced to turn over. If not, pull the top of the motor back slightly and recheck. If there is too much slop between the gears,
push the top of the motor forward. When set properly, the wheels can be spun forward freely with very little noise. Make sure
to tighten both motor screws and replace the gear cover before running.
Tuning Tips
Weight: Adding weight to the front wheels of the Mini-Rock crawler will help increase traction and lower the over center of
gravity. Using the LOSA99201 Self Stick weights, carefully cut each piece in half and place inside the wheel as pictured. It is
important that the wheel weights be evenly placed inside the wheel to ensure that it is balanced.
Shock oil and Springs
The Mini-Rock crawler shocks are filled with Losi 30wt shock fluid. By switching to thinner shock fluid, the Mini-
Rock crawler will have more traction, quicker weight transfer and softer dampening. Doing the opposite will cause
the Mini-Rock crawler to react more slowly to input and have slower weight transfer. Adjusting these settings will
help adapt the Mini-Rock crawler to your conditions. Please note, the Mini-Rock crawler comes from the factory
with a stiffer rear spring to help minimize “Torque Flex” often found in 4WD driver rock crawlers.
Cleaning
Performance can be hindered if dirt gets in any of the moving suspension parts. Use compressed air, a soft paintbrush, or toothbrush to remove dust or dirt.
Avoid using solvents or chemicals as they can actually wash dirt into the bearings or moving parts as well as cause damage to the electronics.
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LOSI MINI-ROCK CRAWLER
• INSTRUCTION MANUAL
LOSI MINI-ROCK CRAWLER
• INSTRUCTION MANUAL
