O.S. engine MAX-25LA User Manual (English)

Other manuals for O.S. engine MAX-25LA

Questions and Answers:

D
David ArroyoJul 31, 2025
What to do if O.S. engine fails to fire?
- W
  Wendy NelsonJul 31, 2025
  If your O.S. engine fails to fire, several issues could be the cause. First, the glowplug battery might be discharged; in this case, you should recharge the lead-acid cell or replace the dry battery. Second, the glowplug element may be burned out, requiring you to replace the glowplug and ensure the applied voltage isn't too high. Third, there might be a problem with the battery leads; try checking the glowplug heating using other leads. Finally, the engine could be flooded due to excessive priming. To resolve this, fully close the needle-valve, remove the glowplug, and flip the propeller to pump out excess fuel, inverting the engine if possible.
S
Stacey YoungAug 4, 2025
Why does O.S. Engine start but revolutions decrease and engine eventually stops?
- E
  Elizabeth LoganAug 4, 2025
  If your O.S. Engine starts, but the revolutions decrease and it eventually stops, it could be due to a few reasons. One possibility is that fuel isn't reaching the engine. Ensure the tank is filled with fuel and check the fuel tubing for any kinks or splits. Also, verify that the carburetor isn't clogged with dirt. Another cause might be that the mixture is too rich. In this case, close the needle-valve half a turn (180 degrees), wait for several minutes, and then restart the engine, priming is not necessary.
M
Matthew LoganAug 9, 2025
What to do if O.S. Engine fires intermittently but does not run?
- S
  Steven GarciaAug 9, 2025
  If your O.S. Engine fires intermittently but doesn't run, the mixture may be too rich. Try closing the needle-valve a little to lean out the mixture.
R
Russell WrightAug 14, 2025
What to do if O.S. Engine fires once or twice, then fails to fire?
- D
  David SchroederAug 14, 2025
  If your O.S. Engine fires once or twice, then fails to fire, continue flipping the propeller. If the engine doesn't start after more than 10 flips, disconnect the battery from the glowplug and leave it for a few minutes. Then, re-energize the plug and flip the prop again. If the engine still doesn't start, remove the glowplug and pump out excess fuel by flipping the prop quickly.
S
shannonpatelAug 19, 2025
How to fix insufficient priming of O.S. Engine?

O.S. engine MAX-25LA Specifications

General

Brand	O.S. engine
Model	MAX-25LA
Category	Engine
Language	English

Summary

O.S. Engine MAX Series Instruction Manual Introduction

Safety Instructions and Warnings Overview

Highlights the critical importance of reading safety instructions and warnings.

Manual Study and Familiarization

Advises thorough reading of the manual to understand engine features and controls.

Manual Storage and Accessibility

Recommends keeping instructions in a safe place for future reference.

Related Equipment Manuals

Suggests keeping aircraft and radio control equipment manuals accessible.

Safety Instructions and Warnings

Understanding Warning Levels

Explains the classification of advice into 'Warnings' (serious injury) and 'Notes' (other dangers).

Specific Safety Warnings

Propeller and Fuel Hazards

Details dangers associated with propellers, fuel flammability, and toxicity.

Operating Environment and Heat Dangers

Warns against enclosed spaces due to carbon monoxide and hot engine parts.

General Safety Notes and Precautions

Engine Purpose and Secure Mounting

Specifies engine use for model aircraft and emphasizes secure mounting.

Silencer Use and Hearing Protection

Advises using the silencer to prevent hearing impairment from engine noise.

Glowplug Handling and Propeller Fitting

Guides on safe glowplug handling and correct propeller installation.

Advanced Safety Notes

Propeller Nut Tightness and Spinner Use

Ensures propeller nut security and correct spinner fit to prevent blade damage.

Safety Equipment and Propeller Clearance

Recommends safety glasses and checks for propeller clearance with linkages.

Propeller Condition and Modification

Instructs on discarding damaged propellers and avoiding unauthorized modifications.

Operational Safety Notes

Throttle Control and Stopping Methods

Details throttle linkage adjustment for stopping and safe engine shutdown methods.

Clothing and Object Hazards Near Propeller

Warns against loose clothing and objects near the rotating propeller.

Starting Area Safety and Spectator Protection

Advises on safe starting areas and keeping spectators at a distance.

Engine Series Introduction

Target Audience and Design Advantages

Introduces engines for beginners/sport flyers, highlighting reliability and cost-effectiveness.

Engineering Excellence and Materials

Discusses O.S. engine quality derived from experience, precision, and materials.

Engine Finish Characteristics

Explains that the 'midnight blue' finish may discolor without affecting performance.

Engine Installation in Model

Beam Mounting Method

Illustrates a typical beam mounting method for the engine.

Radial Motor Mount Option

Mentions the O.S. radial motor mount as an optional extra part.

Fastening Mounting Screws

Details the correct procedure for fastening mounting screws with nuts and washers.

Mounting Beam Alignment

Stresses the importance of parallel mounting beams with surfaces in the same plane.

External Adjustments and Silencer Installation

Needle-Valve Extension Setup

Describes how to install an extension for external needle-valve adjustment.

Silencer Installation and Rotation

Explains how to adjust the silencer's exhaust outlet position.

Tools and Accessories for Engine Operation

Fuel Requirements

Specifies the need for quality glowplug engine fuel, preferably with nitromethane.

Glowplug and Propeller Selection

Details the installed glowplug (A3) and suggested propeller sizes.

Glowplug Battery Power Source

Discusses suitable batteries (1.5V dry cell or 2V lead-acid) for glowplug heating.

Plug Wrench for Tightening

Recommends a plug wrench for glowplug installation, noting an optional long wrench.

Additional Accessories for Engine Operation

Battery Leads for Glowplug Connection

Explains the function of battery leads for glowplug power.

Recommended Fuel Tank Sizes

Suggests specific fuel tank capacities for 10LA, 15LA, and 25LA engines.

Fuel Filling Methods

Describes using squeeze bottles or fuel pumps for filling the tank.

Fuel Can Filter Installation

Advises fitting a filter in the refuelling container to prevent debris entry.

Silicone Tubing for Connections

Specifies silicone tubing for connecting the fuel tank and engine.

Electric Starter and Battery

Recommends using an electric starter and its associated battery for easier starting.

Fuel System Setup and Fuel Selection

Connecting Fuel and Pressure Lines

Details connecting silicone tubing for fuel lines and positioning the fuel tank.

Silencer Pressurized Fuel System

Explains using the silencer to pressurize the fuel tank for steady delivery.

Fuel Selection Criteria and Nitromethane

Advises on fuel quality, nitromethane content, and synthetic vs. castor oil.

Fuel, Glowplug, and Propeller Selection Advice

Fuel Blend Recommendations

Provides a table for methanol, castor oil, and nitromethane blend recommendations.

Propeller Size Recommendations

Lists suggested propeller sizes for different LA series engines.

Glowplug Types and Fitting

Recommends O.S. glowplugs (A3, No.8, A5) and fitting instructions.

Glowplug Function in Engine Operation

Explains the role of the glowplug in continuous ignition and automatic timing.

Glowplug Maintenance and Starting Preparations

Glowplug Lifespan and Replacement

Discusses extending glowplug life and indicators for replacement.

Installing the Glowplug

Provides step-by-step instructions for installing the glowplug correctly.

Installing the Propeller

Guides on installing the propeller and finding the compression point.

Starting Engine Preparations

Checking for Gas Leakage

Details how to check for fuel leaks around the glowplug after installation.

Filling the Fuel Tank Safely

Advises on safely filling the fuel tank, avoiding overflow and contamination.

Engine Starting Procedure: Core Steps

Needle-Valve Adjustment Range

Explains how to open and close the needle-valve for mixture control.

Setting the Initial Needle-Valve Position

Provides initial needle-valve opening settings for different engine sizes.

Engine Priming Process

Describes the procedure for priming the engine with fuel.

Engine Starting Procedure: Priming and Timing

Priming Quantity Significance

Emphasizes the importance of priming quantity for successful starting.

Glowplug Energizing Timing

Notes when to avoid energizing the glowplug during the initial priming phase.

Engine Starting Procedure: Equipment and Action

Securing the Model During Starting

Advises on holding the model securely to prevent movement.

Setting the Throttle for Starting

Specifies the throttle position (1/3 open) for engaging the starter.

Heating the Glowplug

Instructs on connecting the battery to heat the glowplug.

Applying the Electric Starter

Details how to engage the electric starter with the engine.

Engine Starting Procedure: Tuning and Confirmation

Engine Start Confirmation and Starter Removal

Describes confirming engine start and immediately withdrawing the starter.

Initial Needle-Valve Tuning

Guides on adjusting the needle-valve for an optimal exhaust sound.

Engine Starting Procedure: Fine-Tuning Adjustments

Disconnecting Battery Leads Safely

Explains how to disconnect battery leads without touching the propeller.

Fine-Tuning Needle-Valve Adjustment

Details gradual needle-valve adjustments for optimal RPM and performance.

Engine Starting Procedure: Summary and Fine-Tuning

Needle-Valve Adjustment Summary

Provides a comprehensive summary of needle-valve adjustments and exhaust notes.

Subsequent Starting and Engine Stopping Procedures

Simplified Subsequent Starting

Outlines the simplified procedure for starting the engine after initial setup.

Procedure for Stopping the Engine

Explains how to safely stop the engine using throttle control.

Engine Running-In and Carburettor Basics

Engine Breaking-in Procedure

Details the simple running-in process for new engines to settle parts.

Carburettor Function and Control

Explains the throttle-type carburettor and its speed control capabilities.

Carburettor Throttle Control

Carburettor Throttle Control Flowchart

Visual guide for checking and adjusting throttle control for optimal engine performance.

Carburettor Air-Bleed Adjustment

Pre-Flight Carburettor Check

Describes pre-flight checks involving needle-valve and throttle adjustments.

Adjusting the Air-Bleed Screw

Details how to adjust the air-bleed screw for optimal engine running.

Troubleshooting Engine Start Failures

Key Conditions for Reliable Starting

Identifies four essential factors for successful engine starting.

Common Start Failure Symptoms (Part 1)

Lists common symptoms like sluggish rotation and battery issues with corrective actions.

Troubleshooting Engine Performance Issues

Common Start Failure Symptoms (Part 2)

Details symptoms like intermittent running, flooding, and mixture problems with solutions.

Engine Care and Maintenance

Operating Environment and Dust Control

Advises avoiding dusty conditions and using protective surfaces for starting.

Fuel System Maintenance and Filters

Emphasizes fuel tank rinsing, filter installation, and container sealing.

Post-Flight Fuel Management

Recommends draining residual fuel to prevent corrosion after flying sessions.

Exterior Cleaning and Lubrication

Guides on cleaning the engine exterior and internal lubrication for storage.

Long-Term Storage Procedures

Details steps for storing the engine for extended periods (over two months).

Avoiding Unnecessary Disassembly

Discourages unnecessary dismantling of the engine.

Genuine O.S. Parts and Accessories

Radial Motor Mount

Lists part number for radial motor mount for different engine sizes.

Silencer Extension Adaptors

Lists part numbers for silencer extension adaptors.

Exhaust Adaptors

Lists part number for exhaust adaptors.

Glow Plugs

Identifies O.S. Glow Plug A3 and No.8 with part numbers.

Needle Valve Extension Cable Set

Lists part number for needle valve extension cable set.

Long Propeller Nut Set

Lists part number for long propeller nut set for 25LA.

Super Filter (L)

Lists part number for Super Filter (L).

Spinner Nut

Lists part numbers for spinner nuts for 10/15LA and 25LA.

Non-Bubble Weight

Lists part number for non-bubble weight.

Long Socket Wrench with Plug Grip

Lists part number for long socket wrench with plug grip.

Exploded View: MAX-10LA Engine

Engine Parts List: MAX-10LA

Exploded View: MAX-15LA,25LA Engines

Engine Parts List: MAX-15LA,25LA

Carburettor Exploded Views and Parts Lists

Carburettor Type 10H Parts

Provides exploded view and parts list for Carburettor Type 10H.

Carburettor Types 10G, 20H Parts

Provides exploded view and parts list for Carburettor Types 10G, 20H.

MAX-10LA Three View Drawing and Specifications

MAX-15LA/25LA Three View Drawings and Specifications

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