MVVS 35 IFS User Manual

Operating instructions

MVVS 26 IFS č.: 3094IU
MVVS 26 IFS SP č.: 3094SP
MVVS 35 IFS č.: 3098I

Congratulations on choosing the gas engine MVVS 26 ccm (35ccm).
MVVS 26 and 35 has been designed and manufactured for propeller-powered radio-controlled model planes. It is able to
meet all of your expectations of an acrobatic racing engine.

MVVS 26ccm
Bore 33 mm Maximum power output ** 3.8 PS/9000 RpM
Stroke 30.1 mm Maximum torque ** 3.1Nm/8000 RpM
Weight of complete engine
without ignition*
Weight of ignition unit 165 g Lubrication Oil with petrol in mixture 1:40
RpM range 1400 – 9500

MVVS 35ccm
Bore 35.5 mm Maximum power output ** 4.1 PS/8500 RpM
Stroke 35.2 mm Maximum torque ** 3.8 Nm/7500 RpM
Weight of complete engine
without ignition*
Weight of ignition unit 165 g Lubrication Oil with petrol in mixture 1:40
RpM range 1400 – 9000
* 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.
** Power output varies with the exhaust used. The value given in the table stands for the maximum available power
output.

Before using the engine, carefully read these instructions

Technical specifications

936 g Fuel Unleaded 95-octane fuel

1493 g Fuel Unleaded 95-octane fuel

Engine’s dimensions

A

mm B mm C mm D mm E mm
26 IFS 146 99 50 70 60
35 IFS 182 118 60 84 70
F

mm G mm H mm I mm J mm
26 IFS 31 4,3 M10x1 10 33
35 IFS 41 5,3 M10x1 10 45

Safety precautions

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 droved by MVVS engine.

4) Always use original spare parts.

Version 2.1

5) Never tamper with the engine construction.

6) Before each flight 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) Before each flight 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.

8) Periodically check that the engine is firmly fixed to the engine mounts. Never start a loose engine!

9) Always use a balanced propeller! Always replace the propeller when damaged!

8) Make sure that no part of your body intersects the plane of the spinning propeller.

9) Always wear close-fitting, well-fastened clothes when starting or operating the running engine. Never wear

Choke

loosely hanging clothes (ties, scarf, etc.).

10) Never try to stop the engine by any part of your body.

11) Always stop the engine either by turning off the ignition switch or by completely closing the carburetor

throttle valve.

12) Before starting the engine always make sure that the model is safely fixed in place and cannot start moving.

13) Fuel is combustible and therefore must be kept in an enclosed container at a safe distance from the engine

when it is running.

14) When preparing fuel carefully follow the manufacturer’s or dealer’s instructions.

15) Small objects must be kept at a safe distance from the engine when it is running. Never throw any objects

towards the spinning propeller.

16) Be careful in choosing the location where you wish to start the engine. Avoid dusty or sandy areas.

17) Start the engine in well-ventilated areas only. Never start the engine indoors.

18) When starting the engine make sure that bystanders, especially children, are at a safe distance of at least 10

meters.

19) The engine power output makes it possible to fly big models. Mal-operation of such models may cause

serious damage. Start using the MVVS 26 or 35 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.
Oftentimes not 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 top 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 considerably vary. 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.

MVVS 26 and 36 has been designed to generate maximum power at 8500 RpM, according to the type of exhaust used. If
you wish to utilize the maximum power output, choose a propeller which allows the engine to reach these revolutions, or
slightly lower revolutions (given the unloading of the propeller depending on the speed of flight) on the ground.
We do not recommend to use propellers with which the engine reaches more than 9000 RpM. on the ground.

Suggested propeller dimensions:
MVVS 26: MVVS 35:
16x8, 16x10, 16x11, 16x12, 17x8, 17x10, 17x 12, 18x8 18x8, 18x10, 20x8, 20x10, 20x12,21x8, 21x10

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, quality brand-name synthetic oil intended for racing two-stroke engines can be used too.
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.

Since air is used to cool the engine, sufficient air circulation under 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.

Fuel

Assembly

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.

Exhaust

Use only factory-made exhausts pipes designed for this type of engine, preferably brand-name 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 secure sufficient cooling of the
exhaust.

3270 (3271) – compact, medium level of power output
3266 (3268) – tuned pipe, with adaptor 3265 (3269) provides the highest power output, with the flat torque curve, useful

for the model planes

3266 - 3268

3270 – 3271 3265 - 3269

Carburetor adjustment

Basic setting:

(Minutes refer to hands of a clock)

The new engine comes adjusted to the basic setting.

After the engine has been run in, adjust it following the instructions below:

- start the engine and warm it up

- let the engine run at idle speed for approx. 5 seconds

adjusting needle ( L ) for low RpM range 1 turn and 50 minutes
adjusting needle ( H ) for high RpM range 1 turn and 35 minutes
adjusting needle ( L ) for low RpM range 1 turn and 45 minutes
adjusting needle ( H ) for high RpM range 1 turn and 45 minutes

Walbro WT 561 and 793

Step I

engine accelerates quickly and without a hiccup go to Step III. If acceleration is not smooth go on to Step II.

Accelerate to 2/3 of the throttle range within approx. 1 sec (faster acceleration). Repeat three times – if the

for WT 793

for WT 561

H needle
adjusting screw

L needle
adjusting screw

Lever - throttle

Pressure pulse inlet