Serpent S21 User manual
introduction
Thank you very much for choosing a Serpent engine. Read this manual
with great attention before racing the engine, for your own safety as well
as for others, and to ensure you can enjoy your engine for a long time.
The engine is manufactured from precision parts. Always treat the
engine and parts very carefull and avoid dirt and damage at al/ times.
The carburetor of the engine is pre-set in such way that easy starting is
possible.
In case you want to change any setting then follow the manual as per
below. Read very careful/y before making changes. Its always possible
to restare default settings if needed.
running-in
The engine is brandnew and requires a run-in session. This run-in
session will allow oil to lubricate the inner parts of the engine, the piston
and sleeve will get the best possible match and sorne coal will develop
and create a perfect seal inside the engine.
Follow the section Engine run-in carefully. It will protect your engine and
increase performance and lifetime.
serpent s21 engine #130001
2
serpent s21 engine specs oVerVieW
3
GlowPlug
High speed neddle
Low speed neddle
Carburettor
Throttle
lever
Pull Starter
Cooling head
Idle neddle
AIRFILTER:
Makes su re the air that enters the carburetor is clean, so the engine will live longer. The
lter must be oiled well, with a good quality foam airlter oil. Clean and re-oil or replace
after each 5 tanks of fuel.
COOLING HEAD
This helps to keep the engine on the right temperature. During running the head will
become very hot, so never touch with bare hands, and keep away from your bodyparts.
GLOWPLUG
The Glowplug ignites the compressed fuel-air gas-mixture inside the engine. The glowplug
is ignited with a glowplugstarter. When the engine runs the glowplugstarter can be
removed. The glowplug is a normal one (not turbo) and requires a brass shim to seal.
THROTTLE-LEVER
This lever controls the throttle opening.
PULL STARTER
The recoilstarter or pullstarter is used to start the engine, its has a spring inside which will
wind back the rape. Dont pull it too far out.
CARBURETTOR
The carburetor mixes air and fuel into gas and controls the gas-ow going into the engine.
High speed needle: adjusts the overall amount of fuel owing into the carburettor
Low speed needle: adjusts the amount of fuel owing into the carburettor
at idel and low revs ldle speed needle: adjusts the carburettor opening when at idling
INITIAL SETTING:
The carburettor of the engine has been pre-set, so the starting will go as easy as possible.
The standard settings are as following: always start from needle fully in, and screw full
turns out as below:
●High speed needle: adjusts the overall amount of fuel owing into the carburetor
●Low speed needle: adjusts the amount of fuel owing into the carburetor at idle and
low revs.
●Idle speed needle: adjusts the carburetor opening when at idling.
4
starting and using the engine
Run-in the engine
Follow the cold start section as below.
Idling with throttle on radio in neutral position:
●Engine idle is well; this is the case if the car does not roll forward with the engine running
and the throttle in neutral > leave it as it is.
●Engine stops when in neutral > Adjust the idle screw with Y4 of a turn in (clockwise) at the
time, and start again; repeat as needed
●Engine idles too high; in this case the car moves farward with throttle in neutral > Adjust the
idle screw with V4 of a turn out (counter clockwise) at the time until the car does not move
forward anymore and engine idles well.
- Run the car one tank of fuel with this setting. When you run the car apply max 70% of total
power and do not run at 70% or more for longer than a few seconds.
- After 1 tank of fuel, screw in the high speed needle 1/16 turn and run it far 1 tank again.
- Repeat this 5 times in total. Do not lean out the engine too much, as this will cause overheating
and breakage. 1/16 turn out (anti-clockwise) is the minimum necessary.
- Run the engine with same setting far another 5 tanks and apply max 90% throttle .
- After the 10 tanks in total the engine is run-in and can be run at full power.
Cold-start
- Make sure the fueltank is lled to 90% with a high quality commecially available re car fuel
with 25% nitro.
- Perform 5 pulls with the pullstarter without using the Glowstarter and closing the outlet-pipe
of the exhaust with your nger, this will allow gas-mixture to enter the engine.
- Apply the glowplug starter and pull the pullstarter with short fast pulls. As soon as the engine
runs, then lift the car up and apply short strokes with the throttle lever of your radio to warm up
the engine. Remove the glowplugstarter.
- Mount body-shell and start running the car.
- Try to avoid the fueltank from going empty during the run. A tank of fuel will last between 10
and 15 minutes, so refuel before it’s empty, so you continue driving without restarts.
- To stop the engine, press a proper engine stopper with rubber top against the ywheel from
the bottom of the chassis. NEVER use your ngers!
Hot re-start
- Apply the glowplug starter, apply a little bit of throttle on the transmitter, pull the pullstarter
few times until it restarts.
- If after few pulls the engine does not start then let it cool down for 5 minutes and try again.
- In case it still does not start than fallow the instructions in section: Engine does not start.
Setting the carburetor for best performance
Follow the section: start the engine (cold or hot re-start)
1. High speed needle setting:
- Adjust the settting with max 1/16 turn in or out per time.
- After changing the setting apply throttle few times with car of the ground, to allow the engine
to adapt to the new setting
- Run the car again and check carefully the result.
- By turning-in the needle (clockwise) the engine will run leaner (will get less fuel) and the
speed will increase, if you lean the engine too much, the engine will run too hot and damage if
continued too long. If the engine runs too rich (too much fuel) the speed will go down and the
engine may shut down, as the plug cannot ignite the gasses anymore.
- You can also check the correct running with an optional infrared temperature gauge; optimal
temperature is around 100°C.
Notes before to start:
●Before you start the engine, rst switch on the receiver and then the radio and perform all
checks as above.
●When pulling the pullstarter, make sure not to pull out more than 20cm. If you pull out more
the device inside may damage and the rope will not return into the case.
●When the engine is new it need a session of run-in, before the engine can be run at high
speeds, follow the instructions as per below.
●If the engine does not start after 10 pulls, then stop and follow procedure as per below with
title: Engine does not start.
5
starting and using the engine
2. Low speed needle setting
- Adjust the settting with max 1/16 turn in or out per time.
- After changing the setting apply throttle few times with car of the ground, to allow the engine to
adapt to the new setting.
- Run the car again and check carefully the result.
- Watch closely for the smoke coming from the pipe:
●Small amounts of smoke, regular engine sound and fast reaction on throttle > setting is ne,
no adjustment needed.
●A lot of smoke and ‘4-stroking’ sound > mixture is too rich, turn in (clockwise) the low speed
needle with 1/16 turn.
●Engine stops, very little smoke, rpm/revs go up and down mixture is too lean, turn out (anti
clockwise) low speed needle with 1/16 turn per time and try again.
After Running the engine
- Remove fuel from fueltank
- Restart the engine to burn any fuel still left in the engine.
- Remove the airlter to clean/wash out and re-oil or replace the foam fully.
- Insert a few ce of normal engine oil or after run oil in the carburetor and pull the pullstarter
5 times, so the oil can move inside the engine and lubricate and protect the engine against
corrossion; apply a rubber cover over the carburetor intake (in case you do not remount the
airlter yet) to prevent any debris to enter the carburetor during car cleaning or maintenance.
- Wipe of oil and dirt carefully
- Disconnect the receiver battery /switch off.
Engine maintenance
Its best to leave the maintenance of the engine to a service center/rc dealer or experienced user
if you lack experience by yourself. You can learn by fallowing the guidelines of the expert user, or
check out the online video’s on re car engine maintenance.
Problem solving: Issue and >Solution
Engine doesn’t start.
- Too much fuel in the engine. >Remove the glowplug, then pull the pullstarter, so the fuel will be
pushed out. Be carefull far fuelspray and use protective gloves and eye protection.
- No fuel in the engine. >Pull the throttle 5 times quicly and start again. >Check if the pipe-outlet
is not hot anymore, then apply your nger to close the outlet pipe and pull the pullstart 5 times,
check if fuel moves in through the tubing to the engine. Check the silicone tubing and connections
to the carburetor, tank and pipe.
- Carburetor is not open for more than 0.3mm. >Re-adjust the idle screw to allow 0.3mm or more
opening = turn in.
- Glowplug does not glow red when applying the glowbooster.Try another plug.
- Check if the glowbooster battery is charged. Replace or recharge as needed.
Low outside temperature.
Warm up the engine:
- by leaving the car in a warm room for an hour.
- by using a hairdrier.
Engine is overheating. Wait until engine cooled down, turn-out the high speed needle with 1/8
turn and retry.
The carburetor is blocked or dirty > Clean with cleaner spray. Dis-assemble and clean overall.
Air lter is blocked. Remove airlter and check far dirt; clean or replace faam element as needed,
and make sure to oil before use.
Engine adjustment is not correct.>Go back to the standard settings section and re-read the
engine tuning section as above .
For more information on engines and maintenance look
in the Serpent website section downloads and tech-tips:
www.serpent.com
7
notes:
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------
Serpent S21 pullstart engine manual # 13004-1
Table of contents
