O.S. MAX-61VFINSTRUCTIONS FOR O.S. MAX 61 VF ENGINE

The O.S. MAX-61 VF is a high performance engine that has beendeveloped expressly for FAI type R/C contest models. It em-ploys schnuerle scavenging and a rear exhaust port to facilitatethe installation of a tuned silencer system, especially where thelatter is to be built into the fuselage.This engine features specially developed ABC type piston/cylinder construction and a 17 mm O.D. crankshaft of heavyduty alloy steel in order to provide extra power and durabilityand is equipped with an O.S. Type 7D carburettor, speciallydesigned to give good throttle response.Modern precision machinery and carefully selected top-qualitymaterials are employed in the manufacture of this engine toensure consistent performance and long life.

SPECIFICATIONS

DisplacementBoreStrokePractical R.P.M.Power outputWeight

9.95 c.c. (.607 cu. in.)24.0 m.m. (.945 in.) /

22.0m.m. (.866 in.)2,000 ~ 17,000 r.p.m.)1.8 PS (17,000 r.p.m.)528 g (18.6oz.)

INSTALLATIONMount the engine securely on rigid hardwood mounts or metalbearers. For highest performance and safe running, we recom-mend that the bearers should be as heavy and as rigid as possible.Make sure the engine bearers are parallel and their mountingsurfaces are in the same plane. Use 4 m.m. or 6—32 steel screws,such as Alien type, with locknuts, for bolting the engine to thebearers.

RUNNING-IN ("Breaking-in")The special ABC type piston/cylinder construction, two ballbearings, bronze bushed connecting rod, etc., enables this engineto be operated after a shorter running in period. Preliminarybench running can be omitted. However, for long life and peakperformance please observe the following procedure:Install the engine in your model and fly it with a rich needle-valve setting so that it runs at a fast '4 stroke' for the first two orthree flights. Then readjust the needle valve for a slightly lessrich mixture (i.e. at a reduced speed '2-stroke') for the next fourto six flights.

FUELUse a good quality commercial fuel or one of the fuels shown inthe table. "A" is suitable for general use. If higher output isrequired, fuels containing 10 to 20% of nitro methane; (e.g."B")may be used after running in.Lubricants can be either castor oil or synthetics provided thatthey are always of the best quality.

Methanol

Castor Oil

Nitromethane

A

77%

23%

-

B

57%

23%

20%

GLOW PLUGSince the compatibility of the glow-plug and fuel can have a con-siderable effect on performance and reliablity, it is suggestedthat the user selects the R/C type plug found most suitable aftertests. Recommended O.S. glow-plugs are No. 8 and No. 9.

PROPELLERSuggested propellers for pattern flying are 11 x 7-8. Thesuitability of the prop. depends on the size and weight of themodel and the type of flying. Determine the best size and typeafter the engine has been run in. Check the balance of propellerbefore fitting it to the engine. Unbalanced propellers causevibration and a loss of power.Wooden propellers are to be preferred. Some nylon propellersare not strong enough to withstand the high power output ofthis engine and a thrown blade can be very dangerous.

SILENCERAs this engine has been designed primarily for use with a tunedlength exhaust silencer system, a conventional silencer is notsupplied. Any of the tuned pipe silencers currently available for10cc engines may be used by inserting, with the aid of siliconetubing, a short length of 18—20 mm o.d. aluminium tubingbetween the exhaust adaptor (supplied with the engine) and thetuned silencer. The length of the intermediate tube should bedetermined initially in accordance with the instructions issuedwith the tuned silencer and then adjusted, as necessary, in accor-dance with the prop and fuel used, after test flights.Generally speaking, this intermediate tube length will require tobe between 6 cm (2.4") and 10 cm (4"). Alternatively, a specialO.S. exhaust header pipe is available as an optional extra part.

CARBURETTORThe special O.S. automatic carburettor described in the attachedinstruction sheet is fitted, as standard, to this engine. An exhaustpressurised fuel system should be used with this carburettor forbest results.

PARTS LIST

271010002710160227102008271030052670400726705004271060072710700427108001290082192800900245010002

Code No. DescriptionCrankcaseFront HousingCrankshaftCylinder & Piston Assy. (ABC)Cylinder HeadConnecting RodPiston PinCover PlateDrive WasherWoodruff KeyPropeller WasherPropeller Nut

Code No.2711300426714006266170049R73100227130000290810042908171927126109

*27126202*72101300*72101103

DescriptionScrew SetGasket SetPiston Pin RetainerBall Bearing (Front)Ball Bearing (Rear)Carburettor Complete (7D)Carburettor RetainerExhaust Adaptor CompleteExhaust Header-Pipe CompleteSilicone Tubing SetTuned Silencer

Optional partsThe specification is subject to alteration for improvement without notice.

Exhaust Header-Pipe Silicone Tubing Tuned Silencer

O.S. ENGINES MFG CO LTD6-15 3-chome Imagawa Higashisumiyoshi-kuOsaka 546, Japan. TEL. Osaka (06) 702-0225

57912