Moki2008 

# User Guide for MOKI Glow Engines

...is this a MARK or a MOKI? The powerful MARK engines are manufactured in Hunga ry by MOKI Motor – previously known as MOKI. Throughout the world, the brand name MOKI has b ecome the synonym of performance and dependability amongst demanding modelers – for comp etitions just as much as for the plain fun of the hobby. As famous as the brand name MOKI has become, unfortunately some ownership issues around the copyright of the name have occurred. For this r eason MRC has chosen to re-brand the engines under the name MARK. So – regardless whether you ow n a MARK or a MOKI – your engine has been developed by some of the most experiences model eng ine experts and has been assembled by hand in Hungary to live up to your highest expectations. 

# History MOKI/M/ARK engines have been manufactured since more than fifty years. The Hungarian Department of Defense founded MOKI in 1957 with the charter of developing and manufacturing engines for the use in airplane models as well as f or military purposes. This heritage can still be fo und in the name MOKI : the acronym stands for “ Modell Kisérleti Intézet ”, which in Hungarian means “Institute for Experimental Modeling”. Until 2008 t he factory has resided at the original location at the airport of Budaörs, a few miles west to the center of Budapest. Until 1989, the entire production capacity was rese rved for use by the competition modelers (airplanes, cars and boats) in Hungary and the army . The engines became famous due to the successes of Hungarian modelers, but there was no c ommercial pressure on production. This unique situation allowed the development team to focus on performance and dependability – the elements most important for success. Hungarian modelers have gathered about two hundred European and World Championship titles, and a long list of world records. Many modelers partici pated at races, while at the same time working for MOKI. One famous example is Mr. Gyula Krizsma – World Champion in high-speed control-line flight in 1962 – and the engineer responsible for the develop ment of MOKI’s two-stroke engines. Until today, his designs form the basis of the successful line-u p of MARK engines. The experience grown in more than fifty years of ma nufacturing high-performance model engines has survived all economical and political changes broug ht about by the fall of the iron curtain in 1989. N ow a company in private ownership, the team is concent rating on fulfilling the demands of modelers world-wide for dependable, high-performance engines

. Our motto is “ Competition quality for the demanding modeler ” . Stringent, industry-level quality assurance processes and modern CAD and CNC equipmen t combined with half a century’s worth of experience are an excellent base to provide you wit h powerful, long lasting engines of classical desig n. Numerous tests in magazines and an impressive track record of international prizes are the testimonials to our claim. We strive to preserve th ese values for the future.Moki2008



# Technical Data

Please note that the performance and RPM figures de pend strongly from external factors such as barometric pressure / altitude, fuel and propeller used etc. The figures given above relate to typical measurements done at the factory.



## Dimensions

Displacement cubic inches Displacement

cubic cm Bore mm Stroke mm Max. R.P.M. Performance kW / HP Weight

M 51 0.51 8.37 22.5 21 12,500 0.65 / 0.9 390g / 13.76 oz

M 61 0.61 9.97 23 24 17,500 1.62 / 2.2 495g / 17.46 oz

M 135 M140 1.38 22.6 31.5 29 13,000 2.86 / 3.9 855g / 30.16 oz

M 180 1.82 29.8 35 31 12,000 3.0 / 4.1 1170g / 41.27 oz
M 210 2.11 34.6 36 34 10,000 3.3 / 4.5 1275g / 44.97 oz
M 360 2 x 1.82 2 x 29.8 35 31 11,000 5.7 / 7.8 2270g / 80.07 ozMoki2008

(All dimensions below in millimeters)



### A B C D E F G H I J K L

M 51 45 26 85 72 39 8 36 52 - - 39 28
M 61 51 28 93 83 44 9 42 60 - - 45,5 28
M 135 M 140 60 35 112 102 57 9 51 71 85 22,5 54 40

M 180 68 36 126 112 62 10 56 80 100 32 56 34
M 210 70 38 127 118 64 11 60 82 100 30 61 34
M 360 68 36 195 112 62 - 56 80 - - 56 34



# Precautions Throughout this User Guide we assume, that you have already gathered experiences in operating a glow engine, and that this is not the first engine you operate. Should this indeed be your first experience with a glow engine, we strongly recommen d that you seek professional advice from a more experienced modeler, for example in your club, or f rom the reseller who has sold this engine to you. The power and performance of MOKI engines can be ver y dangerous if the engine is not handled with the appropriate precaution, serious injuries or eve n fatalities can be the result if insufficient care is taken. Please read the entire manual carefully befo re attempting to start the engine.

• The engine most be mounted firmly to a test bench o r into a model, the model or the test bench must be fixed appropriately.

• A suitable, balanced and undamaged propeller of app ropriate size must be used.

• The original propeller nut or another suitable prop eller nut must be used and tightened firmly. Using spinners with thick back-plates and/or propel lers with an unusually thick hub can lead to insufficient grip of the propeller nut. In this cas e a special adaptor must be used to ensure that the propeller and the spinner are held in plac e firmly. Please contact us or a third-party, specialized company (e.g. TruTurn) to acquire a sui table adaptor.

• Carefully check the tightness of the propeller nut on a regular basis. Some materials (like wood) have a tendency to be compressible by the pro peller nut, leading to a loose propeller nut. 

# Breaking-In a New Engine Breaking-in (sometimes also called running-in) your new engine carefully is an important measure to ensure longevity as well as high performance. You c an either mount the engine to a test stand, or install it into your model. It is important that th e engine gets sufficient cooling and that the prope ller is not oversized. Please use a quality fuel with at least 20% oil con tent and no nitro methane for the first hours of operation. Using a high quality castor oil in this phase makes sense and shortens the required time until the engine is run-in. If you prefer not to us e castor due to its unpleasant side effects (like s ticky exhaust residues, intensive odor), you can also use synthetic oil. Please consider that due to the better lubrication with synthetic oils the time req uired until the engine reaches its peak performance may take a bit longer. In any case, make sure you u se first-class quality fuel or fuel components.Moki2008

At the beginning, the carburetor’s main needle shou ld be set in such a way that the engine does not rev higher than 5-6,000 rpm at full throttle. Run t he engine in short intervals of about five minutes, which you can subsequently increase by a minute aft er each run until you reach ten minutes. Allow the engine to cool out entirely between two runs (t his is very important, as the temperature changes contribute significantly to the process). After the first few intervals you can start leaning the main needle click by click. NOTE : If the engine revs start decreasing (“sagging”), immediately open the main needle several clicks, as sagging revs at a co nstant throttle setting are a sure indicator for overheating. After the first few intervals you should also try c hanging revs with the throttle – as soon as the eng ine safely holds an idle without a connected glow drive r it’s time to get the model in the air. Flying is a much better way of running-in the engine, as the co oling is much better, the static load on the engine is lower and the operation at alternating revs is g ood for the engine. Avoid long full-throttle phases , and change revs as often as you can. You can tell that the engine is broken in as soon a s the engine holds a peak rev without sagging, and you can dial-in a low, steady idle. Now you can als o reduce the oil content in your fuel to about 17% of a high-quality synthetic oil (if you use castor, please do not reduce the oil content, stay at 20%) . A very important notice: Many times we have heard tha t “an experienced colleague”, “the club’s engine guru” or “the guys at the field” have said somethin g like “My engine of the brand xyz runs perfectly with x% oil (x being a very low figure like 8 or 12 )”. Please, DO NOT LISTEN TO SUCH INCOMPETENT STATEMENTS . First of all, we believe that we, as designers an d manufacturers of our fine engines, do know best what the engine has been designed for. Secondly, the required amount of oil differs due to several facts and depends ver y much on the design specifications. A highperformance engine like ours has much tighter fitti ngs than some of the competitor’s engines – this is true for the connecting rod bushings as well as for the hand-selected cylinder/piston pair. The small tolerances used in these parts are an important con tributor to the reliability and dependability of ou r engines. Low oil content not only can cause lubrica tion problems, but it also increases the engine temperature (thus increasing wear) and provides no reserves should you experience a lean run due to e.g. wrong carb setting, the pressure line on the m uffler failing etc.. Please note, that our warranty does not cover any damages to the connection rod, p iston or cylinder due to overheating or the use of insufficient or bad quality oil. 

# Installing the Engine The engine can be mounted to your model either via the mounting lugs or with the help of the coneshaped engine mount available as an accessory for s ome of our engines. This engine mount replaces the standard rear cover of the engine and can be at tached directly to our model’s firewall. Make sure to replace the standard rear cover mounting screws with the longer ones that come with the engine mount. The Mark M360 In-Line Twin should always be mounted with the special engine mount available for this engine. Although the cone-shaped engine mount of the M180 mechanically also fits the M360, it should not be used as the engine’s length and the s heer power it produces cannot be mounted securely using the cone. Please do take the engine’s power and high torque i nto consideration when mounting it to your model, especially if you use any rubber elements. Be caref ul as some types of rubber disintegrate over time under the influence of oil and fuel. Always use a l ocking compound on the screws used for engine mounting.
Make sure that there is sufficient air flow to cool the engine. The air stream should flow directly to the cylinder and cylinder head. If you use any cowl, ma ke sure that the air outlet has at least twice the opening area of the air inlet – hot air expands and thus needs a larger exit to ensure a proper flow. When installing the M360 In-line Twin particular ca re should be taken to ensure that the rear cylinder is appropriately cooled.Moki2008

The following symptoms are clear indicators of over heating:

• Loss of power / sagging revs at full throttle despi te correct carburetor settings

• Frequently fouled glow plugs (you can diagnose over heating before the plug fails – the coil should be shiny, and the plug body should not be di scolored. If you see any discoloration, or the coil is not shiny, then the engine has been exp osed to overheating).

• Loosening cylinder head screws – this is a severe a larm signal and a clear indicator of intensive overheating! If you observe any of these symptoms, take action a nd ensure that your engine gets adequate cooling. This will ensure a long life and reliable high performance.



# Fuel Tank and Fuel Lines
The fuel tank should be installed in the model in s uch way, that the centerline of the tank is on the same height as the engine’s needle valve. This ensu res a constant and steady flow of fuel. Use foam to protect the tank against vibration, and use muff ler pressure to pressurize the tank. Please use fue l tubing (including the tank’s plumbing, any filters or filling valves) of an adequate diameter, to ensu re that there is sufficient fuel flow under all condit ions. If you notice, that you can turn the needle v alve counterclockwise without any effect on the engine’s r.p.m., you have probably installed insufficiently sized fuel tubing.



# The Carburetor The carburetor used on MOKI engines uses a needle v alve to regulate the engine’s high speed fuel mixture. The fuel mixture from idle to mid-range is controlled by an idle disk. On the same side as the needle valve you can find a knurled disk. This disk has a little groove on the top, and a “+” and “-“ symbol are punched on its fa ce. By turning the disk into the “+”-direction, the fuel mixture for idle and mid-range is made richer (so more fuel can flow), turning the disk into the “- “-direction provides a leaner mixture. Please chang e the setting of the disk only in very small steps! The factory setting of the disk is with the groove exactly on top center. For the time being, do not change the factory setting! The main needle is delivered separately in the box. Carefully insert the needle into the valve, and gently screw it in all the way. Do not apply any fo rce. After the needle has been completely screwed in, turn the needle valve out three full revolution s. With this base setting – main needle valve out three revolutions and idle disk centered – the engi ne should start and run in any case. Only minor changes to the main needle and the idle disk should be required to obtain the maximum power and a reliable idle. Please note that the ideal carbureto r settings depend on the viscosity of the fuel, the barometric air pressure at your flying site (altitu de), relative humidity and temperature of the air – just to mention a few factors. Please find below ho w to find the optimum settings. 

# Starting the Engine MOKI engines are really easy to start, and can easil y be hand started – provided you have the required practice. Always use a stick when starting the engine by hand! Please keep in mind that highperformance glow engines like the MOKI engines can c ause serious injuries if handled improperly. For this reason, we strongly recommend to use an electr ic starter. If you prefer starting the engine by hand, ALWAYS USE A STICK and protect your hands with heav y leather gloves

. 

# Optimizing the Carburetor Settings This chapter explains how to get the best performan ce once the engine has been run-in. Begin by starting the engine, and allow the engine to warm-u p, if necessary, with connected glow power. AfterMoki2008

a few minutes, remove the glow power, and slowly ad vance the throttle to full power (make sure that the model is well secured, ideally a helper should hold it). Adjust the main needle valve so that the engine reaches its peak rpm, then open the needle v alve (counterclockwise) until the rpm drops by about 500 rpm. Always keep the engine on the “rich” side when flying! Check that the engine runs stable also with the model’s nose held straight up. A slight increase in revs is OK, but should you nee d to open the needle valve so much, that no clean run ning is possible once the model returns into a horizontal attitude, then probably the tank is inst alled incorrectly (too far from the engine, or too high/too low in relation to the carburetor). Once yo u are satisfied with the engine’s setting at full power, reduce the throttle to a low idle and let th e engine run at idle for a few minutes. Check if th e engine’s acceleration is quick and without any sput tering or hesitation. If the acceleration is not satisfactory, return the engine to idle, and briefl y pinch the fuel line with your fingers. If the eng ine revs up, stop the engine and turn the idle disk a v ery small amount towards the “-“ sign, if the engin e suddenly stops without first revving up, turn the i dle disk a small amount towards the “+”. After changing the idle disk’s setting, check the main ne edle’s setting at full throttle as described above. Repeat the process until you are satisfied. 

# Shutting off the Engine All glow engines produce a fair amount of exhaust r esidue containing acids and organic solvents. As long as the engine is hot, these corrosive residues will evaporate and exit through the exhaust. However, if you let the engine run at idle revs for a while, the engine will cool down and the residue will condensate and be trapped in the engine’s exha ust system as well as the crank case. The colder the outside temperature, the larger the exhaust, th e stronger this effect! It is therefore very import ant to ensure, that after the last flight of the day, t he engine is shut off at full temperature. It is go od practice to allow the engine to run at full power f or one or two minutes, before shutting the engine o ff by closing off or pinching the fuel line (do not st op it by covering the carb inlet, this will draw additional fuel in the crank case and will contribu te to the build-up of corrosive residues). Make sur e that the exhaust is drained from any residues, and store the model with the engine pointing upwards – this prevents any residues to flow back into the engine. Please note that damages caused by corrosion are not covered by the warranty! 

# Selecting the Best Suitable Propeller The choice of a suitable propeller depends on many factors, such as the characteristics of your model, your style of flying, the fuel you use, the type of exhaust system, the atmospheric conditions etc. Please note, that the same nominal size of propelle r can deliver quite different results from brand to brand. In the case of wooden propellers even two pr opellers of the identical size and the same brand can deliver very different results. For this reason , the table below can only serve as a rough indicat ion of typical propeller sizes – the best is to try sev eral prop sizes until you find your favorite. The f irst number denotes the propeller’s diameter; the second number represents the pitch (all measurements in inches). Please make sure not to exceed the maxi mum rev number in the table to prevent the engine from damages. Please note that the rev figur es measured on a static model on the ground will be considerably lower than the peak rpm reached in flight – so keep a safety margin of at least 1000 rpm. MOKI engines are designed to deliver a very hig h torque; therefore you can use relative larger diameter props at lower revs. Not only will this re nder a better efficiency, it also contributes to lo wer noise emissions. Please observe the following guidelines:

• Only use undamaged propellers

• Don’t use propellers with an unknown history

• Heavy propellers (carbon fiber, composites) have a larger “flywheel”-effect and allow for a lower idle while wooden propellers result in a bris ker acceleration of the engine

• Any discoloring on the surface of a plastic propell er is an indication of structural damage – do not use any props with such marks, discard them!

• Propellers have to be balanced carefullyMoki2008

• Take utmost care when enlarging the hole in the pro p hub – use a drill press, or ream it by hand

• If you use a spinner make sure that the spinner is balanced and use the appropriate fastening nut. Please consult your MOKI dealer for special pro peller nuts with an integrated thread for a spinner mounting screw. These are available both fr om MARK as well as manufacturers of spinners.
Displacement cm3 Propeller size (2 blades) Max. R.P.M. M 51 8,37 10 x 9 – 12 x 6 12,500 M 61 9,97 10 x 12 – 12 x 10 17,500 M 135 M 140 22,6 14 x 12 – 18 x 6 13,000 M 180 29,8 17 x 12 – 19 x 8 12,000 M 210 34,6 18 x 12 – 20 x 10 10,000 M 360 2 x 29,82 22 x 10 – 24 x 8 11,000 

# Exhaust System Suitable exhaust systems are available from many br ands. Consult your MOKI engine dealer for the ones available in your market. If you plan to use a tuned pipe system, please make sure that you use the adequate length of header pipe. The longer the pipe is, the lower the RPM when the resonator effect kicks in. If the pipe is too short, the engi ne will have a tendency of overheating. Another important factor is the muffler’s volume: if the mu ffler is too small, too much unburned exhaust gasses will flow back from the muffler into the eng ine. The typical symptom is that when cutting the throttle, the engine will not fall back to idle qui ckly, but will continue to run at a medium RPM leve l for several seconds. If you experience this symptom, yo u can try adjusting the mid-range of the carb slightly leaner, or increase the area of the muffle r’s exit pipe. If these measures don’t help you wil l have to switch to a muffler with a larger volume. 

# Maintenance and Repair Should you ever need to repair your MOKI engine, gen uine spare parts are available through your MOKI dealer. Do not disassemble the engine unless yo u have the necessary skills, practice and tools. Please note that any disassembly by unauthorized pe rsons will void the manufacturer’s warranty. 

# Warranty MOKI engines carry a two year manufacturer’s warrant y. In case your MOKI engine needs a repair in the warranty period, return the engine in its origi nal packing, along with a proof of purchase, to you r dealer or send it directly to the manufacturer. Ple ase include a description of the problem and includ e all details about the fuel, propeller and glow plug used. Please note that the warranty will be void if any u nauthorized disassembly has taken place. Furthermore the warranty explicitly excludes covera ge of all damages caused by corrosion, overheating and crashes.