HoBao Mac Star 28 Owner's manual

For your safety - Your engine is not a toy!
• You will be working with highly flammable fuel, so keep it away from exposed flames or
any thing which might ignite it. Read the safety info on the fuel container.
• Do not use fuels that were not designed for glow plug engines.
• Keep the fuel out of reach of children!
• Deadly carbon monoxide gas will be released, so do not operate the engine in an enclosed area
where exposed flames or sparks can ignite it, or where it causes you to inhale it for prolonged
periods.
• During operation, the engine may be dangerously hot to the touch.
• Do not use the engine for purposes other than in model cars designed for them.
• Mount the engine securely.
NITRO ENGINE INFORMATION
Mac Star 28
IMPORTANT - READ THIS BEFORE
STARTING YOUR ENGINE!
Before Starting Your Engine
Oiling the filter
The air filter is essential for keeping dirt out of the engine. A foam
filter must be oiled before running the engine. We recommend using
Associated AS7710 foam pre-filter treatment. Dab the treatment all around
the filter, put the filter in a plastic bag and knead it until the filter is
saturated, but not soaked. NEVER RUN YOUR VEHICLE WITHOUT THE AIR
FILTER.
Adjustments
Your engine has come factory set to allow for an easy start and rich
running . DO NOT alter any of the settings until the running in period
has been completed.
Putting fuel in the fuel tank
Squeeze the fuel bottle, put the bottle’s tube into your fuel container,
and draw out some fuel. Lift up the lid on the fuel tank, and slowly
squeeze the fuel bottle until the tank is full. Be careful here. If you
overflow the tank it might get on your radio gear or on your brakes and
you may create an unsafe driving situation. Always keep your fuel bottle
closed when not in use.
Understanding the engine terms “rich” and “lean”
Your carburettor has screws that regulate how much air and fuel enter
the engine together, the air/fuel mixture. An air/fuel mixture that is too
“rich” means there is too much fuel, and a mixture that is too “lean”
means that there is not enough fuel for the given amount of air. When the
mixture is too rich, performance will be sluggish (one symptom of this, is
excessive amounts of smoke from the exhaust). There is also a potential
to foul the glow plug when the mixture is too rich. When the mixture is too
lean, there is not enough fuel to cool or lubricate the internal engine
components, and damage to the engine and/or glow plug is almost
certain.
CAUTION:
If, while you are driving, the engine stalls because of an overheating
condition, severe damage may have already occurred. Overheating is
caused by the following conditions.
• Fuel mixture is set too lean
• Air leak around carb
• Loss of muffler pressure (line falls off)
• Excessive nitro content in the fuel
• Incorrect oil content in the fuel
• No air filter
• Poor quality of fuel
• Contaminated fuel
• Excessive loads on the engine (locked drivetrain)
Your engine will be short-lived if any of the above conditions are
allowed to exist for any length of time.
During the first few tanks watch closely
for any signs of overheating. These will include:
• Steam or smoke coming from the engine surfaces
• Cleaning out and then lagging during high-speed acceleration, as if it
is running out of fuel.
• Popping or clattering sound when slowing down.
Idle speed will surge or possibly diminish to the point of stalling.
To Test For Overheating
It’s important to check the head temperature during the operation of
the engine. The best method for checking the head temperature is to use a
head temperature gauge. There are several head temperature gauges
available, and the temperature readings between these different brands of
gauges vary. Due to this variance , the temperature readings will range
between approximately 185 degrees and 225 degrees. About 185 degrees
is the normal for the Hyper 21. If you don’t have access to a head
temperature gauge, you can use water to check the head temperature.
Place a drop of water on top of the cylinder head. If it sizzles away
immediately, shut down your engine. If it takes approximately 3-5 seconds
for the water drop to boil away, then the engine is running within a normal
temperature range.
Start Your Engines
Running-In
The modern model car engine requires relatively little running in, due
to the use of ABC piston and liner assembly. The engine should be run on
a rich setting for approximately 6-8 tanks of fuel, with another 6-8 at a
slightly less rich setting. Once this has been completed, the internal
engine components should be properly seated and a normal setting can
be used. A good idea is to use a running in fuel for this purpose, as it is
especially designed for breaking in new engines without damage.
The best methods of checking on the running setting of the engine, is
to first check the smoke trail coming out of the exhaust with the car is
running. A very rich setting would allow the car to pull away slowly or
slugglish with a momentary hesitation and lots of smoke from a standing
start. When the car is accelerating at full throttle, the engine will never
“Clean Out”. When an engine cleans out, the speed and the rpms will
increase suddenly and dramatically, as if the engine has switched to
second gear. Also, the amount of smoke that comes from the exhaust will
decrease. Cleaning Out is a desirable characteristic once the engine is
fully broken in.
As the engine reaches normal operating temperature, it will speed up
and performance will increase. This occurs because the fuel mixture is
becoming leaner with the increased temperature. You will need to richen
the fuel mixture so that the engine continues to run as described above.

When the first tank is almost gone, bring the car in and shut off the
engine. Allow the engine to cool for 8 to 10 minutes before starting the
engine up again. Add more fuel. Start it back up and run the second tank
of fuel. Again allow the engine to cool before starting it up again.
The key to breaking in your engine is patience. During the break in
period , your engine may appear to malfunction with problems such as
stalling, inconsistent performance, and fouling out glow plugs. Don’t give
up. These are just a few things you may go through during the break in
period. Just keep it running, apply the throttle on and off as smoothly as
you can. Sudden bursts or quick releases of the throttle can stall your
engine. Soon after break in your patience will pay off with a well running
engine. The performance level of the
engine will be limited by the “rich’ fuel mixture which you will use all
during the break-in process. Once the engine is fully broken-in the mixture
can be “leaned out,” and speed and acceleration will increase. Because of
the rich fuel mixture and the wearing of the new parts, deposits will form
on the glow plug causing it to fail. Expect to replace the glow plug during
the break in period, and definitely when the engine is fully broken in and
the fuel mixture is leaned out.
Setting Engine for Normal
Tuning High Speed
As you approach the first 6-8 tanks running you can start to
GRADUALLY adjust you engine for normal performance. PLEASE NOTE any
adjustments need to be very small at 1/8th turn increments. You can then
begin adjusting the fuel mixture to maximize performance for your driving
needs. To lean turn the main fuel control needle in a clockwise direction.
This will allow the car to pull away faster and more cleanly, without
hesitation and increase the top speed. There should however still be a
noticeable smoke trail.
If the main needle is screwed in too far thus allowing the engine to
run too lean, it will seem to run strong at first, but will bog, hesitate,
or stall when running at high speed. The engine will also rapidly
overheat when the setting is too lean. This is because fuel includes
lubrication, and that lubrication is inadequate when the setting is too lean.
CHECK THE ENGINE TEMPERATURE OFTEN AS YOU LEAN THE MIXTURE. DO
NOT LET THE ENGINE OVERHEAT. You should always see smoke coming
from the exhaust.
At the optimum setting, the engine will clean out; have a strong-
sounding, high-pitched whine at full speed; and there will be a thin trail of
whitish smoke coming from the exhaust. It is always better to set the
engine a little rich rather than too lean.
If the engine stalls on acceleration, begins to bog or slow down at full
throttle, or if there is a reduction in exhaust smoke, then the engine is
running too lean. Immediately turn the high speed mixture screw
counterclockwise 1/4 of a turn and operate the car at medium speeds for
1 to 2 minutes to allow the engine to cool.
Tuning Low Speed
The low-speed mixture affects how the engine will perform in the low
to mid range rpms. Turning the low-speed needle clockwise will lean the
mixture. As with the high-speed
mixture, leaning the low-speed
mixture increases performance.
Again, if the mixture here is set too
lean, the engine may be starved for
lubrication in the lowand mid-rpm
ranges, thus causing overheating
and excessive engine wear.
Perform the following test to
determine if the low speed mixture
is set correctly. With the engine
warm and running, allow it to idle
for approximately 15 seconds. Now
quickly apply throttle and note the performance. If the engine bogs,
accelerates erratically, and a large puff of blue smokes emitted, then the
low speed mixture is too rich. Turn
the low-speed screw clockwise 1/8
of a turn. If the engine speeds up
for a moment then bogs, hesitates,
or stalls, then the low speed
mixture is too lean. Turn the screw
counterclockwise 1/8 of a turn.
Adjust the mixture screws in 1/8 of
a turn increments, wait 15
seconds, and retest after each
change. Adjust for the best
acceleration without the car
stalling.
Care and Maintenance
When you are finished racing for the day, drain the fuel tank.
Afterwards, energize the glow plug with your glow plug starter and try to
restart the engine in order to burn off any fuel that may remain inside the
engine. Repeat this procedure until the engine fails to fire. Try to eject
residue while the engine is still warm. Finally, inject some corrosion
inhibiting oil, and rotate the engine to distribute the oil to all the working
parts. Do not, however, inject the oil into the carburetor, for it may cause
the O-rings inside to deteriorate. When cleaning the exterior of the engine,
use WD-40. Do not use gasoline or any solvents that might damage the
silicone fuel tubing.
Cleaning the air filter. When the air filter starts to get dirty, do the
following steps:
Step 1. Clean the foam with fuel. Do this by pouring a little fuel in a small
can and kneading the filter in the fuel. When it looks cleaner, then
dispose of the fuel.
Step 2. Dry the filter. Squeeze out the fuel with a paper towel until it’s dry.
Step 3. Apply Associated’s #7710 Foam Pre-Filter Treatment to help keep
the dirt out. Dab the treatment all around the filter, put the filter in
a plastic sandwich bag, and knead it until the filter is saturated,
but not soaked.
Troubleshooting
Glow Plug Problems
The glow plug in your engine is an inexpensive consumable item
which must be replaced periodically to maintain peak performance and
starting ease. Most often, any starting problems or erratic performance
can be traced back to the glow plug. The glow plug should also be
checked if the engine’s acceleration and top speed performance suddenly
becomes flat. The only sure way to test for a faulty glow plug is simply
install a new one to see if the problem goes away. Remove the plug from
the cylinder head with a 5/16” nut driver. Make sure there is no dirt or
debris on top of the head which could fall into the engine. Do not loose the
copper gasket which seals the glow plug. Touch the glow plug to the
contacts of the glow plug starter. All of the coils should glow white.
Sometimes the first few coils will not glow while the rest are bright, most
likely indicating a bad plug. If the glow is dim orange, then the glow
starter battery should be replaced or recharged.
At the high rpm that the engines operate only a top quality plug will
cut the mustard. Therefore we recommend the use of either McCoy MC9
or RB #6 plugs.
Fuel Mixture
The fuel mixture is the largest variable you have to control while
operating your engine.
Fuel brand, ambient temperature, and humidity all effect how your
mixture should be set. If the engine runs great one day but runs rich or
lean the next day, it is probably the result of a change in the air quality
and temperature. This should be expected and adjusted for.
Although there are many fuels on the market, very few are designed
to perform and protect your engine at the likes of 35,000rpm that some of
our engines can attain. It is with this fact in mind, and our own in house
testing that we
ONLY RECOMMEND the following fuels:
Byron RACE Gen2, Byron RACE Gen2
RTR and Model Technics Dynaglow.
Keep between 10 and 20% nitromethene
content for running and first use. The single
most popular reason for engine failure or
unreliability is poor or wrong fuel. These
fuels have been tested with our engines
and we are confident of their
performance.
OTHER FUELS MAY WORK
WITH OTHER ENGINES BUT
THE FUELS LISTED WORK
BEST WITH THESE ENGINES.
FAILURE TO KEEP TO THESE
FUELS MAY RESULT IN
DAMAGE OR REDUCED
PERFORMANCE AND VOID
ANY WARRANTY CLAIMS.
HIGH SPEED
ADJUSTMENT
IDLE
ADJUSTMENT
LOW SPEED
ADJUSTMENT

Pull Starter Hints
The pull starter as fitted to most of the entry level engines is, if
treated correctly, the easiest and most cost effective method of starting an
engine. As with every silver lining, there is a cloud. The pullstart system is
similar to that of a lawnmower to look at, but that is where the similarity
ends. The pullstarter is susceptible to breaking if the engine is flooded or
not lubricated enough. To ensure this does not happen, a few simple rules
should be followed.
1. Before attempting to start the engine from cold, remove the
glowplug and then prime the engine with fuel. For cars with a primer
button
on the tank, press this until the fuel has travelled along the fuel pipe
to the carburettor and then a further 10-20 presses. For cars without a
primer on the tank, pull the pullstarter rapidly with your finger over the
exhaust pipe outlet until the fuel has travelled to the carb, and then a
further 10-20 times to lube the engine.
2. Then turn the car upside down and pull the pullstarter rapidly until
all the excess fuel has emptied onto the floor through the glowplug hole.
Refit the plug ensuring the copper gasket washer is also refitted. Wind it
all the way in and then re-wind 1 to 1.5 turns. This allows gases to escape
thus lowering the engines initial compression.
3. Start engine. The engine will run “lumpily” or stop after a few
seconds so try and keep it running by blipping the throttle. Tighten the
glowplug while the engine is running if possible. If the engine has stalled
restart with the plug tightened.
The above procedure hould always be followed from cold or if
difficulty with starting is being experienced.
Flooding of the Engine
The most common cause of engine and pullstarter damage is from the
‘flooding” of the engine or a hydro-locked. More accurately this is too
much fuel inside the engines crankcase causing the piston to lock. The
piston rises to the top of the combustion chamber and instead of
compressing a gas i.e. fuel/air mixture it has to try and compress a liquid,
fuel only, which isn’t possible. This puts massive strain on the piston,
conrod and crankshaft as well as the starter. Invariably one component
will fail, usually the conrod causing massive damage to the engines
internals.
To avoid flooding the engine, always start the engine from cold using
the methods mentioned above and if at any time the engine becomes
difficult to turn over with the pullstarter, then remove the glowplug and
empty all excess fuel out and start again. The pullstarter assembly can
only be damaged by a flooded engine, so if you break a pullstarter, this is
a warning that your are flooding the engine.
Cooling Problems
Engine overheating is most often caused by running the engine too
lean or because the cooling air for the cylinder head is blocked. If the
mixture is too lean, simply allow the engine to cool, richen the mixture and
try it again. Bodies must have holes cut in them to allow for cooling air to
circulate over the surface of the cylinder head. On most bodies, it is a
good idea to cut part of the wind-shield out and part of the back window
to allow for additional cooling.
Soloution
Fill fuel tank
Replace fuel
Charge glow starter
Replace glow plug, see “Glow Plug Problems”
See “ flooding” section.
Allow engine to cool, richen fuel mixture, check airflow
Readjust carburetor
Clean exhaust system
Clean air filter
Clear excess fuel, see “flooding” Section.
Repair starter.
Examine engine for damage.
Increase idle speed.
Check for holes in the fuel line.
Replace glow plug, see “Glow Plug Problem” section.
Allow engine to cool, richen fuel Mixture, check airflow
Replace pressure hose- clear
Check flow to and from the tank.
Set high-speed mixture to a leaner setting
Check glow plug gasket
Replace fuel
Clean Carburetor
Stop the engine- find the cause
Use a lower gear ratio
Replace clutch shoes
Find the bound item and repair
Richen high-speed mixture
Get air to the head
Use fuel with lower nitro
Check for bound up drive train
Richen low-speed mixture
Richen high-speed mixture.
Lean low-speed mixture.
Stop the engine and find the cause.
Check for holes in fuel line.
Test or replace plug
Replace glow plug.
Richen low-speed mixture.
Lean high-speed mixture.
Add fuel
Increase idle speed.
Description
Engine will not start
Starter will not pull
Engine starts and
then stalls
Engine sluggish /
poor performance
Engine overheats
Engine hesitates or
stumbles
Engine stalls instantly
when throttle is fully
opened from idle
Engine stalls while
driving around turns
Problem
Out of fuel
Improper or contaminated fuel
Glow starter not charged
Glow plug bad
Engine flooded
Engine overheating
Carburetor incorrectly adjusted
Exhaust blocked
Air cleaner blocked
Engine is flooded
Rope is jammed
Engine seized
Idle speed set too low
Air bubbles in fuel line
Glow plug is fouled
Engine is overheated
Insufficient fuel tank pressure
Blockage at exhaust header fitting
High-speed fuel mixture is too rich
Leaking glow plug
Fuel bad or contaminated
Carburetor dirty or blocked
Engine overheating
Engine over geared for application
Clutch slipping
Bound up drive train
High-speed fuel mixture is too lean
Cooling air is being blocked
Excessive nitro in the fuel
Excessive load on the engine
Low-speed mixture too lean
High-speed mixture too lean
Low-speed mixture too rich
Engine overheated
Air bubbles in fuel line
Glow plug fouled
Glow plug fouled
Low-speed mixture too lean
High-speed mixture too rich
Fuel level is low
Idle speed set too low
Troubleshooting Quick Glance

MNV
TAS
STNV
SFN
CML Distribution. Saxon House, Saxon Business Park, Hanbury Road, Bromsgrove, Worcestershire. B60 4AD. England
Tel: [phone] Fax: [phone] E-mail: [email protected] Web site: www.cmldistribution.co.uk
Factory Settings for Mac Star 28
All new engines are assembled with what we will term ‘factory
settings’. These settings should allow almost all engines to be started up
and allow for minimal adjustment for running in purposes.
Bearing this in mind, we are offering you the opportunity of re-
adjusting to the ‘factory settings’ based on engines currently held in stock.
Main Needle Valve (MNV)
Screw down until resistance is met, and no further movement is apparent.
RE-OPEN 4.5 FULL TURNS.
Supply Fuel nozzle (SFN)
This nozzle should not extend beyond the body it is screwed into.
SET FLUSH WITH CARBURETTOR BODY END FACE. (basically leave as
received from the factory).
Throttle Adjustment Screw (TAS)
Gently shut off carburettor sliding body and slowly re-open by means of
adjusting screw.
ADJUST SCREW UNTIL APPROX 1MM OF APERTURE APPEARS BETWEEN
THE END OF THE THROTTLE BODY AND AIR INTAKE APERTURE.
Sub Throttle Needle Valve (STNV)
With adjustment screw setting in place, close off the throttle body against
the screw. Very gently screw in the needle valve until it closes off the
supply fuel nozzle (21059) and is prevented from re-opening by the entry
of the needle valve into the centre hole of the fuel nozzle (work with great
care with this one - we are only looking for minimal frictional contact
between both parts).
RE-OPEN VALV E 2.5 TURNS.
Glossary of Carburettor Functions
Main Needle Valve (High Speed)
The main needle mixture screw controls how much fuel enters the engine
during mid- to high-speed operation. The screw is turned clockwise to
lean (less fuel) and anti-clockwise to richen (more fuel)
Sub Throttle Valve (Low Speed)
This screw meters the fuel at low speeds. The low-speed mixture screw is
located in the end of the carburetor, inside the throttle arm.
This screw controls how much fuel enters the engine at idle and low
throttle. This adjustment will smooth the idle and improve the acceleration
to mid speed. Make this adjustment with the throttle closed, after setting
the idle. The screw is turned clockwise to lean (less fuel) and anti-
clockwise to richen (more fuel)
Throttle Adjustment Screw
The throttle adjustment screw regulates the throttle opening to control the
idle speed. The screw is turned clockwise for a higher idle speed and anti-
clockwise for a lower idle speed.