Ski-Doo Formula MX, Formula Plus & Formula Mach I Snowmobile 1985-1989 - Comprehensive Shop Manual
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Purchase Information
1985-1989 Ski-Doo Formula MX, Plus & Mach I Snowmobile Shop Manual - Technical Specifications
- Document Number / Seller:
- 28104 / Jerry Allen
- File Size:
- 12.58 MB
- File Type:
- Language:
- English
- Pages:
- 389
- Printable:
- Yes
- Estimated Download Time:
- 0.26 Minutes
- Delivery Format:
- Digital (PDF) - Instant Access
- Category:
- Snowmobile
- Brand:
- Ski-Doo
- Reviewed and Approved:
- Jan 1, 2026
Ski-Doo Models and Parts Covered in this Snowmobile Manual
- Ski-Doo Formula MX (1985-1989)
- Ski-Doo Formula MX (H/A) (1985-1989)
- Ski-Doo Formula MX LT (1985-1989)
- Ski-Doo Formula Plus (1985-1989)
- Ski-Doo Formula Plus LT (1985-1989)
- Ski-Doo Formula Mach I (1985-1989)
- Ski-Doo Formula MX 3720 (1985)
- Ski-Doo Formula Plus 3721 (1985)
- Ski-Doo Formula MX 3725 (1986)
- Ski-Doo Formula Plus 3726 (1986)
- Ski-Doo Formula MX (H/A) 3727 (1986)
- Ski-Doo Formula MX 3728 (1987)
- Ski-Doo Formula Plus 3729 (1987)
- Ski-Doo Formula MX LT 3730 (1987)
- Ski-Doo Formula MX 3732 (1988)
- Ski-Doo Formula Plus 3733 (1988)
- Ski-Doo Formula MX LT 3734 (1988)
- Ski-Doo Formula MX 3735 (1989)
- Ski-Doo Formula MX LT 3736 (1989)
- Ski-Doo Formula Plus 3737 (1989)
- Ski-Doo Formula Plus LT 3738 (1989)
- Ski-Doo Formula Mach I 3739 (1989)
Complete Manual Information
Ski-Doo Formula MX, Plus & Mach I Snowmobile Shop Manual - 1985-1989
This shop manual serves as the primary technical resource for the maintenance, troubleshooting, and complete overhaul of the specified Ski-Doo snowmobile models. To ensure maximum engine uptime, mechanics must pack a low-temperature grease into the oil seal lips prior to installation to maintain sealing integrity under extreme sub-zero operational parameters. Technical procedures within this document range from routine periodic lubrication to sophisticated engine and suspension system architecture restoration.
Technical Applicability & Model Identification
The following models are covered under the scope of this manual, identified by their primary four-digit vehicle model number:
- 1985 Series Configurations
- 3720: Formula MX
- 3721: Formula Plus
- 1986 Series Configurations
- 3725: Formula MX
- 3726: Formula Plus
- 3727: Formula MX (H/A - High Altitude)
- 1987 Series Configurations
- 3728: Formula MX
- 3729: Formula Plus
- 3730: Formula MX LT
- 1988 Series Configurations
- 3732: Formula MX
- 3733: Formula Plus
- 3734: Formula MX LT
- 1989 Series Configurations
- 3735: Formula MX
- 3736: Formula MX LT
- 3737: Formula Plus
- 3738: Formula Plus LT
- 3739: Formula Mach I
Performance & Operational ROI
- System Longevity: Adherence to factory-specified torque sequences prevents fastener failure and structural stress on aluminum components.
- Operational Safety: Detailed testing procedures for Capacitor Discharge Ignition (CDI) systems eliminate high-voltage hazards during diagnostics.
- Parts Accuracy: Precision measurement benchmarks for cylinder bore taper and out-of-round conditions ensure optimal compression and fuel economy.
Document Metadata
- Manual Type: Factory Shop Manual
- Applicable Years: 1985, 1986, 1987, 1988, 1989
- Measurement Standards: Dual Metric and U.S. Customary Units
Technical Depth & Factory Benchmarks
Rotary valve timing and ignition synchronization represent the critical calibration data for these powerplants. Piston-to-cylinder clearance and ring end gap specifications are provided for 462.8cc, 521.2cc, and 580.8cc engine variants to maintain factory-level power output. Detailed resistance values for primary and secondary ignition coils provide a definitive baseline for electrical system integrity.
Visual Navigation Aids
System architecture is illustrated through high-resolution technical drawings and photographs. This manual includes:
- Detailed exploded views of the RAVE (Rotax Automatic Variable Exhaust) system on 583 engines.
- Step-by-step photographic guides for primary and secondary sheave disassembly.
- Full-scale wiring diagrams for ignition, lighting, and sensor circuits.
- Internal cross-sections of fuel pump and carburetor assemblies.
Table of Contents
- Chapter One: General Information (Serial Numbers, Fasteners, Tools)
- Chapter Two: Troubleshooting (Engine, Electrical, Drive System)
- Chapter Three: Lubrication, Maintenance and Tune-up
- Chapter Four: High-Altitude and Rear Suspension Adjustment
- Chapter Five: Engine (Rotary Valve, RAVE, Crankcase)
- Chapter Six: Fuel and Exhaust Systems (Carburetor, Fuel Pump)
- Chapter Seven: Electrical System (CDI, Voltage Regulator)
- Chapter Eight: Oil Injection System
- Chapter Nine: Liquid Cooling System
- Chapter Ten: Recoil Starter
- Chapter Eleven: Drive System (Clutching, Belt Deflection)
- Chapter Twelve: Brake, Chaincase, Jackshaft and Drive Axle
- Chapter Thirteen: Front Suspension and Steering
- Chapter Fourteen: Track and Rear Suspension
- Chapter Fifteen: Off-Season Storage
- Appendix: Wiring Diagrams and Index
Operational Limits & Specifications
- Cylinder Head Torque: 20 N-m (15 ft.-lb.) for 1985-1988 models; 22 N-m (16 ft.-lb.) for 1989 models.
- Fluid Capacities: Cooling system requires 4.2 L (142 oz.) of a 60:40 ethylene glycol-based mixture.
- Lubrication Specification: Rotary valve reservoir (1985-1988) requires 455 cc (16 oz.) of specified lubricant.
- Ignition Gaps: Standard spark plug gap is 0.40 mm (0.016 in.) for most models, increasing to 0.45 mm (0.018 in.) for the Formula Mach I.
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Frequently Asked Questions - Ski-Doo Snowmobile Manual
What does this Ski-Doo manual cover?
This comprehensive service manual covers detailed repair procedures, maintenance schedules, troubleshooting guides, and technical specifications for Ski-Doo Formula MX, Formula Plus & Formula Mach I Snowmobile 1985-1989 - Comprehensive Shop Manual. It includes information for the following models: - Ski-Doo Formula MX (1985-1989) - Ski-Doo Formula MX (H/A) (1985-1989) - Ski-Doo Formula MX LT (1985-1989) - Ski-Doo Formula Plus (1985-1989) - Ski-Doo Formula Plus LT (1985-1989) - Ski-Doo Formula Mach I (1985-1989) - Ski-Doo Formula MX 3720 (1985) - Ski-Doo Formula Plus 3721 (1985) - Ski-Doo Formula MX 3725 (1986) - Ski-Doo Formula Plus 3726 (1986) - Ski-Doo Formula MX (H/A) 3727 (1986) - Ski-Doo Formula MX 3728 (1987) - Ski-Doo Formula Plus 3729 (1987) - Ski-Doo Formula MX LT 3730 (1987) - Ski-Doo Formula MX 3732 (1988) - Ski-Doo Formula Plus 3733 (1988) - Ski-Doo Formula MX LT 3734 (1988) - Ski-Doo Formula MX 3735 (1989) - Ski-Doo Formula MX LT 3736 (1989) - Ski-Doo Formula Plus 3737 (1989) - Ski-Doo Formula Plus LT 3738 (1989) - Ski-Doo Formula Mach I 3739 (1989).
Is this manual suitable for beginners?
Yes, this Ski-Doo manual is designed for both professional technicians and DIY enthusiasts. It includes step-by-step procedures with clear illustrations and safety guidelines for Snowmobile maintenance and repair.
What file format will I receive?
You will receive this manual as a PDF file (12.58 MB), which is compatible with all devices. The manual is fully searchable and printable for your convenience.
How quickly can I access the manual after purchase?
You'll receive instant access to your Ski-Doo Snowmobile manual immediately after payment completion. The download link is valid for 3 days, with lifetime re-download guarantee.
Can I print specific sections of the manual?
Absolutely! This digital manual allows you to print any section you need, from individual pages to complete chapters, making it perfect for workshop use.
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