MVVS 50 IRS User Manual
Before using the engine, please read these instructions carefully.
Operating instructions
Congratulations on choosing the MVVS 50 gas engine.
MVVS 50 IRS No: 3005L/3005S
Version 1.3
The MVVS 50 has been designed and manufactured for propeller-powered radiocontrolled model planes. It is able to meet all of your expectations of an acrobatic racing
engine.
Technical specifications
Bore 40 mm RpM range 1000 – 7500 RpM
Stroke 38 mm
Weight of complete
engine without ignition*
Weight of ignition unit 190 g Lubrication
* Some manufacturers state the weight of incomplete engines. The value in the table
above stands for the weight of a completely assembled engine, including the spark plug,
carburetor, drive washer and prop screws.
1) Never use the engine for any manned vehicles.
2) When operating model planes, always follow the rules and laws in effect in your
country.
3) The manufacturer declines all responsibility for all damages arising from the
operation of models and other appliances powered by the MVVS 50 engine.
4) Always use original spare parts.
5) Never tamper with the engine construction.
6) Before each flight always check that all the propeller screws are tightened up and in
good condition. If you use a spinner, check that it is tightened up, too. When
mounting the spinner always follow the assembly instructions.
7) Periodically check that the engine is firmly fixed to the engine mounts. Never start a
loose engine!
8) Always use a balanced propeller! Always replace the propeller when damaged!
9) Make sure that no part of your body intersects the plane of the spinning propeller.
10) Always wear close-fitting, well-fastened clothes when starting or operating the
running engine. Never wear loosely hanging clothes (ties, scarf, etc.).
11) Never try to stop the engine by using any part of your body.
12) Always stop the engine either by turning off the ignition switch or by completely
closing the carburetor throttle valve.
13) Before starting the engine always make sure that the model is safely fixed in place
and cannot start moving.
1560 g Fuel
Safety precautions
Unleaded 95-
octane fuel
Oil with petrol in
mixture 1:40
14) Fuel is combustible and therefore must be kept in an enclosed container at a safe
distance from the engine when it is running.
15) When preparing fuel carefully follow the manufacturer’s or dealer’s instructions.
16) Small objects must be kept at a safe distance from the engine when it is running.
Never throw any objects towards the spinning propeller.
17) Be careful in choosing the location where you wish to start the engine. Avoid dusty
or sandy areas.
18) Start the engine in well-ventilated areas only. Never start the engine indoors.
19) When starting the engine make sure that bystanders, especially children, are at a safe
distance of at least 10 m.
20) The engine power output makes it possible to fly big models. Mal-operation of such
models may cause serious damage. Start using the MVVS 50 in model planes only
after you have mastered operating smaller models.
Selecting a suitable propeller
It is usually the case that propellers of the same dimensions coming from different
manufacturers are not the same. Sometimes even propellers of the same dimensions
produced by a same manufacturer are not the same. The engine power is best utilized
when the propeller dynamics curve and engine power curve (revolutions/power output)
intersect in the area of the engine’s maximum power output. Unfortunately, no propeller
manufacturer provides this information. Engine power output is also a variable quality. It
depends above all on the silencer used and can vary considerably. The situation is further
complicated by environmental parameters (temperature and atmospheric pressure in
particular): low temperature and high pressure increase propellers’ input requirements by
20% in comparison with input at hot weather.
Suggested propeller dimensions: two blade: 22x10, 22x12, 22x14
23x8, 23x10, 23x12
24x8, 24x10, 24x12
three blade: 21x10, 21x12, 22x8, 22x10
These values are only approximate and may vary with the factors described in the
previous section, as well as with the type of the exhaust system used.
The MVVS 50 has been designed to generate maximum power at 6100–6300 RpM,
according to the type of exhaust used. If you wish to utilize the maximum power output,
choose a propeller, which allow the engine to reach these revolutions, or slightly lower
revolutions (given that the unloading of the propeller depends on the speed of flight) on
the ground.
We do not recommend using propellers with which the engine reaches more than 7500
RpM on the ground.
When fixing the propeller to the engine tighten the central nut and each screw several
times over. Finally tighten the washer screws once again in sequence across each other.
Fuel
Always use unleaded 95-octane petrol mixed in the proportion 40 volume units of petrol
to 1 unit of Mobil Racing 2T oil. If necessary, any quality brand-name synthetic oil
intended for racing two-stroke engines can be also used.
Running the engine in, use the MVVS Racing 2T oil, that comes with the engine. Mix it
in the proportion 30:1.
Never use inexpensive oil developed for garden appliances or synthetic oils intended for
the operation of methanol model engines. The manufacturer declines all responsibility for
all engine damages arising from the use of low-quality fuel.
Store fuel in containers designed for this purpose. Do not use mixed fuel older than 90
days.
Assembly
The engine is fastened in place by means of the four holes in the rear cover. The rear
cover is adjustable by 90° which ensure easy access to the carburetor’s operating
elements. The engine can be mounted directly to the firewall or an assembly kit can be
used (special accessories). Use M6 screws or screws M5 with a reduction kit (special
accessories). If you decide to fasten the engine using flexible motor mounts, always
choose parts with enough solidity and strength. Make sure to secure the screws against
loosening and regularly check that they are tightened up and in good condition.
Since air is used to cool the engine, sufficient air circulation through the cowl must be
ensured. Never forget about a hot air outlet – which must be bigger than the intake. Gas
engines heat up to a much greater degree than methanol ones!
Do not forget that the engine needs oxygen from the air to be able to operate. Therefore
ensure access of air to the engine intake as well. Caution: intake of warm air from
beneath the cowl may cut the engine power output.
Caution! When mounting the engine in the model use seals to protect all openings and
prevent the pollution of the engine’s inside with sawdust, residual abrasives etc. Make
sure that the inside of the fuselage is clean and that all parts are tighten in place and
cannot be sucked inside the engine.
Exhaust System
Use only factory-made exhausts pipes designed for this type of engine, preferably brandname MVVS engines with which you also get the power output guaranteed.
The manufacturer declines all responsibility for all engine damages arising from the use
of improper exhaust systems.
When mounting the exhaust follow the manufacturer’s instructions. Make sure to ensure
sufficient cooling of the exhaust.
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