OFNA Racing Ultra MBX User Manual
1:8 SCALE GAS POWERED OFF-ROAD BUGGY
INSTRUCTION MANUAL
PLEASE READ INSTRUCTIONS CAREFULLY BEFORE ASSEMBLING
THIS MODEL.
KEEP THIS MANUAL FOR PARTS NUMBERS WHEN ORDERING.
ULTRA
MBXMBX
PIVOT BALL KNUCKLE ARM TYPE
SPECIFICATION ARE SUBJECT TO CHANGE WITHOUT NOTICE.
REQUIRED FOR OPERATION
THINGS NEEDED
Glow Fuel
20%
AA Batteries ( 12 pcs )
#10211 NiHm Flat Pack
You will need to buy a few items to start the engine and run the car.
• Use 20% nitro CAR fuel. Do not use airplane or heli fuels, they will
over heat engine.
• Buy long glow plugs, like OFNA/PICCO Plug (#51007). Use plugs
without idle bar. Do NOT buy hot plugs, like the MC-59.
In your box you will find..
• #10163 - Bottle, spout top
• #10218 - Red “C” size glow heater
You need to get batteries for the radio transmitter and the car receiver
packs.
• Radio TX needs (8) eight AA batteries
• Car needs (4) four AA batteries.
Recommendation Option:
You may want to upgrade the car battery pack to a Ni-Cad or NiHm 5
cell type(600AE). This will give more run time. OFNA #10211
1000NiMh Flat Pack and NiHm Battery Charger #10214
TOOLS NOT INCLUDED IN KIT
Phillips Type Screw Drivers ( L )
Phillips Type Screw Drivers ( S )
Needle Nose Pliers
Knife
Instant Cement
Cutter
Curved Scissors
Masking Tape
Brush
Cross Wrench
#17109 $3.95
Paints
Glow Plug & 17MM Cross Wrench
#10801 $6.95
Grease
READ THIS BEFORE RUNNING
Running a nitro kit is fun and easy, but to make this a safe rusting.
and good experience you must observe a few rules. This
kit is extremely fast, easily over 40MPH, and can seriously
injure someone if you are not careful.
Where to run car?
• Any running area you choose must be dry. Do not run
car near any water or wet dirt.
• Do not run on public streets. It is very easy to have the
car run over or damaged by hitting the curb.
• Do not operate car in tight confined places. The car is
very fast and will easily hit something.
• Do not run near people or animals.
and will too easily hit someone.
• Due noise, you will want to consider the surrounding
area when operating the car.
• Do not operate the car at night. You will not be able to
drive it without hitting something.
• Do not operate the car indoors. Engine exhaust is not
healthy.
Glow Fuel
• Glow fuel is poisonous!
• Glow fuel is flammable!
• Do not leave in fuel bottle with lid off at any time. label for additional precautions.
• Don use any fuel other than glow fuel in this engine.
First Time Starting the Engine
Caution! When starting engine make sure the following is
observed. • Always turn off the car BEFORE turning off radio.
• Set engine Master needle to 3 turns (rich setting)
• Do not do this alone, get an experienced friend to help at • DAMAGE DUE CAR RUN AWAY IS NOT A WARRANTY
first. ISSUE.
• Fill fuel tank, try not to spill fuel. Do not spill fuel on
receiver
• Hold car off the ground, so it will not runaway when first
starts
• Turn on Radio and check the linkage before starting
engine.
• Turn on car receiver battery switch.
• Always have an air filter on the carburetor to keep dirt
out.
The car is very fast
• Clear oil and dirt from chassis with a degreaser.
Precautions
• This kit is not a toy. Always run car with a second
person as a spotter and pitman.
• Hot Parts - The pipe, manifold, engine and head are very
hot and will cause burns.
• Rotating Parts - Keep hands away from the drive train,
wheels, and engine when engine is running.
• Radio - Check batteries life before running the car. If
radio does not have full control of the car with steering
and/or throttle/brake do not run until corrected. Failure to
correct this will result in possible injury and damage to the
car or property.
• Glow fuel - Do leave the glow fuel unattended with the lid
off. Fuel contains Methanol and Nitro Methane and is
flammable and poisonous.
Store fuel in cool ventilated location. Refer the glow fuel
• Car Fuel tank - Never store fuel in car tank, it will ruin the
engine if left in tank.
IF YOU DO NOT BREAK-IN ENGINE
CORRECTLY, MAINLY AT LOW RPM,
YOU WILL BREAK THE CONNECTING
ROD!
Engine Break-in
• See Engine Page.
Emergency Stopping Engine When Running
• Remove air filter and cover carb. intake.
• Squeeze fuel line and hold until engine stops.
• With a rag, cover exhaust outlet.
Storing Car After Running
• Remove fuel from tank and fuel lines
• Turn off radio in car
• Put a few drops of after run in engine to keep it from
FAILURE TO NOT READ AND
FOLLOW BREAK-IN ENGINE
INSTRUCTIONS WILL VOID
WARRANTY!
ASSEMBLY OF THE THROTTLE LINKAGE SYSTEM
#30800
Plastic Throttle
kit
Throttle
Spring
Plastic Collar
* Take the plastic collar
from brake system plastic
parts.
3X3mm
Set Screw
#30530
Plastic Throttle
Ball Joint
2mm Rod
3X3mm
Set Screw
#10300
Alum.Stopper
Place battery pack in a plastic bag before
securely tie wrap pack to radio plate. Pack
will fall out if not securely mounted! Check
the battery pack if you have any radio
interference, don’t run car if you see a
problem..
* Snap On.
Brake
Idle Position
Full Throttle
3X3mm
Set Screw
#10300
Fuel
Tube
( 6mm )
Alum.Stopper
* Align throttle servo same
as shown.
CHECKING ENGINE THROTTLE
A
1. Insert AA batteries into
transmitter (8 Pcs).
2.Turn on transmitter.
3.Turn on receiver.
4.Center throttle trims as
shown .
IMPORTANT
CHECK RADIO THROTTLE
AND STEERING SWITCHES
BEFORE RUNNING CAR
* Insert into transmitter.
1. Pull Full Throttle.
B
C
1. Push trigger to full
brake position.
2. Adjust alum. Stopper to
increase or decrease
the brake.
B
A
* Align throttle servo same
as shown.
Brake (C)
A
Idle Position (A)
Full Throttle (B)
• Full throttle arm position.
Spring rod pulls throttle
barrel open and brake
rods release pressure on
brake cams.
C
B
C
• Full brake arm position.
Spring compresses
forward and brake rods
pull brake levers.
INSTALLATION OF THE TIRES AND WHEELS
Front Knuckle Arm
Assembly
Wheel Nut
Notic direction of the tire.
* use spring clips to adjust spring
Tension if needed.
Wheel Nut
Notice direction of the tire.
ASSEMBLY OF THE BATTERY
Insert 8 pcs AA batteries into transmtter.
Rear Hub Assembly
Antenna wire
Antenna pipe
AA Batteries 4 pcs
*Tighten the strap and
cut off the excess.
Receiver battery case
SHOCK ASSEMBLY
1mm
Washer
2mm
Washer
32237
Rebuild
7mm
E-Ring
* Note the E-Ring must
fit into groove as shown.
Kit
* Fit into groove.
Oil Seal
32203
Dust Pusher, Short
(Yellow Rubber)
32205
Dust & Shaft
Protector, long
*Push onto shock
cylinder.
32292
Front. 3.5mm
Short Shaft
Shock Shaft
* Short shaft
for front.
2.6 x 5mm
Washer
* Assembly 4 pieces of the
shock shaft .
30671
Front Shaft, 3.5mm
with Piston
Piston
2.6mm Nut
Scre
Ce
men
w
t
32051
E-Ring
6mm Ball End
( Make 2 for front.)
( Make 2 for rear. )
32051
6mm Ball End
FILLING THE SHOCKS WITH OIL
1. Pull down piston and pour oil into
shock cylinder. Remove air bubbles
by slowly moving piston up and down.
Silicone
Oil
2. Pull down piston, attach pressure top
and shock oil overflow with tissue
paper.
*Leave 3mm.
32043
Cap, blue
32236
Rear, 3.5mm
Long Shaft
3. Tighten up shock cap.
* Long shaft
for rear.
30672
Rear Shaft, 3.5mm
with Piston
* Be careful not to damage shock shaft.
* Screw down cap.
UP
down.
*Move Slowly.
ASSEMBLY OF THE SPRING
Spring Holder
30403
6mm
Ball Joint
* Push 6mm ball joint
into ball end.
32330
Set, Red Springs, Front & Rear
32340
Set, Yellow Springs, Front & Rear
32033
Pressure Top
Fit into groove.
*
32051
Misc. Plastic Shock Parts
*Slide spring collar into Shock.
Spring Collar
32051
Misc. Plastic Shock Parts
(Standard)
1mm
3mm
5mm
*Spring Tension adjust .er
ASSEMBLY OF NEW “K” STYLE DIFFERENTIAL CASE AND GEARS
31324 - FRONT OR REAR DIFF UNIT
31325 - CENTER DIFF UNIT
30779
2 x 12.8mm
Pin
* Position the O-ring
as shown.
30751 Diff. Case ( Front/Rear )
30761 Diff. Case (Center )
30779
2 x 12.8mm
Pin
30771
Diff. Shaft
30779
P5 O-Ring
( Orange )
30779
0.5 x 26mm
O-Ring
30769
Diff. Bevel Gear
( Large )
30779
4 x 10mm
Washer
* Apply diff. Gear grease to the
differential, during assembly.
* Fill the diff. Case to
approx 70% with grease.
Grease
30769
Diff.
Bevel Gear
( Small )
30773
4mm
Cross Pin
30769
Diff.
Bevel Gear
( Small )
30773
4mm
Cross Pin
30779
4 x 10mm
Washer
30769
Diff.
Bevel Gear
( Small )
30779
4 x 10mm
Washer
NB. It is very important to remove
the 30779 shim if the mesh
is too tight.
30771
Diff. Shaft
30769
Diff.
Bevel Gear
( Large )
ASSEMBLY OF THE BEVEL GEAR
( Builds two differentials for front and rear. )
30120
Bevel Gear
(Large/Metal)
31010
Optional - Bevel Gear
(Harden Steel)
30121
3mm
Tube
30779
P5 O-Ring
( Orange )
30121
3 x 5mm
Screw
30751 Diff. Case ( Front/Rear )
30761 Diff. Case (Center )
Sc
rew
Ce
me
nt
36730
Cap Joint
90026
5 x 5mm
Set Screw
30620
7 x 19mm
Bal lbearings
90026
5 x 5mm
Set Screw
3x10mm
Tapping Screw
3x10mm
Tapping Screw
Scre
Cem
w
t
en
* Push 3mm tubes into
holes of the diff. Case.
* Notice the straight holes
are for front and rear.
30121
3mm
Tube
30121
3 x 5mm
Screw
(Small Head)
5 x 5mm
Set Screw
3 x 5mm
Screw
30620
7 x 19mm
Ball bearings
39730
Cap Joint
ASSEMBLY OF THE SPUR GEAR
M3
Nylon Nut
31040
Bevel Gear
( Large )
* Notice the tapered holes
are for the center diff. Only.
3 x 10 mm Flat Head
Screw
ASSEMBLY OF THE CENTER DIFF. MOUNT
30620
30170
Brake Joint
90026
5 x 5mm
Set Screw
Screw
Cement
3 x 15mm
Screw
30180
Brake pad
steel
7 x 19x 5mm
Bal lbearings
30200
Center Diff. Housing
( Front )
31020
Brake Disk
30620
7 x 19x 5mm
Bal lbearings
30111
3x10mm
Flat Head Screw & Nuts
30200
Center Diff. Housing
( Rear )
90026
5 x 5mm
Set Screw
30170
Brake Joint
Screw
Cement
5 x 5mm Set Screw
3 x 15mm Screw
31020
Brake Disk
30180
Brake pad
steel
3 x 15mm
Screw
ASSEMBLY OF THE CENTER DIFF. AND BRAKE CAM
Screw
3 x 3mm
Set Screw
30210
Brake Cam
Cement
30171
Brake Lever
* Notice: The direction of the
brake cam.
30210
Brake Cam
* Take the plastic bearing
from 30800 brake system
plastic parts.
30651
Center Plate
30212
option,
ball Bearing, 2 pcs.
30211
Plastic
Bearing
3 x 10mm
Tapping Screw
30211
Plastic
Bearing
3mm
* Leave 3mm distance between
brake cam and nut.
30171
Brake Lever
Screw
Cement
3 x 3mm
Set Screw
0.5mm
3 x 3mm Set Screw
3 x 10mm
Tapping Screw
ASSEMBLY OF THE GEAR BOX
( Assemble two gear boxes for front and rear. )
30010
1
30630
6 x 13 x 5mm
Ball Bearing
* Insert two ball bearings
as shown.
3
Gear Box
30010
Gear Box
Screw
Cement
36730
Cap Joint
30630
6 x 13 x 5mm
Ball Bearing
2
5 x 5mm
Set Screw
* Make two gear boxes for front and
rear.
* Place set screw in D cut.
30130
Bevel Gear
Front Diff. Assembly
Note direction when installing!
3 x 20mm Flat Head
Tapping Screw
ASSEMBLY OF THE FRONT SHOCK TOWER
30160
Front Arm Pin
Holder
4 x 10mm
Tapping Screw
4 x 10mm
Tapping Screw
30010
Gear Box
Cover
30100
Front Shock Tower
4 x 20mm
Flat Head
Tapping Screw
Tower mounting
screws.
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