Ski-Doo Formula MX, Plus & Mach I 1985–1989 Snowmobile Shop Manual (P/N S829)

Clymer’s Ski-Doo Snowmobile Shop Manual 1985–1989 (P/N S829; ISBN 0-89287-521-6) covers Formula MX, MX (H/A), MX LT, Plus, Plus LT, and Mach I models. This is an aftermarket Clymer repair publication, not a Bombardier factory/OEM manual.

PDF Bookmarks, Wiring Detail and Page Count

Search and diagram access: PDF text search and text copying are unavailable. Embedded bookmarks link to the contents, Quick Reference Data, all 15 chapters, the index, and wiring diagrams. Small wiring labels and connector details require zooming in the checked diagrams.

One printable English PDF contains 389 pages: 374 chapter pages, four contents pages, four Quick Reference Data pages, one title page, three index pages, and three wiring-diagram pages. These reference and introductory pages are included in the total.

Engine, Clutch and Chassis Repair

The following selected repair topics outline the coverage. Other subjects include emergency rope starting and general bearing-replacement techniques.

• Engine repair: Step-by-step engine removal and installation, cylinder-head service, piston and ring inspection, cylinder honing, crankcase separation, rotary-valve timing, and RAVE service.

• Fuel and altitude tuning: Mikuni VM34, VM38, and VM40 carburetor service, float-height checks, synchronization, fuel-pump repair, altitude/temperature jetting charts, clutch calibration, and gearing.

• Electrical diagnosis: Ignition Troubleshooting chart, CDI and ignition-coil testing, charge- and lighting-coil checks, voltage-regulator diagnosis, and lighting, switch, and sensor service.

• Oil injection and cooling: Oil-pump adjustment, bleeding and component service, thermostat testing, water-pump and heat-exchanger work, hose inspection, and cooling-system flushing.

• Clutches and final drive: Primary and secondary sheave service, belt alignment and tension, mechanical disc-brake repair, chaincase and jackshaft work, and drive-axle adjustment.

• Steering, track and suspension: Steering geometry, track tension and alignment, rear-suspension removal, shock inspection and spring replacement, slide-shoe service, and track-cleat repair.

The manual expressly includes first-time do-it-yourselfers through professional mechanics in its readership. Major engine and suspension work still requires mechanical judgment, measuring equipment, and the specified pullers, presses, or spring tools.

Engine Variants and Overhaul Limits

Separate top-end exploded views distinguish the 467 engine used in MX variants, the 537 in 1985–1988 Plus models, the 536 in the 1989 Plus and Plus LT, and the RAVE-equipped 583 in the 1989 Mach I. RAVE coverage extends through removal, inspection, disassembly, and assembly.

Crankshaft inspection and outer-bearing replacement are described. Disassembly of the pressed crankshaft to replace internal bearings, seals, or the central gear is referred to a qualified dealer or crankshaft specialist.

Piston-service cautions explain how driving a tight wrist pin can damage the piston, needle bearing, and connecting rod.

Carburetor Setup and Lubrication Differences

The Carburetor Circuit Guide relates the pilot, needle, and main circuits to throttle opening. Separate PTO- and MAG-side calibration tables help distinguish the settings for each carburetor rather than treating the pair as interchangeable.

The fuel chapter warns that running or adjusting the engine without its air silencer can produce a lean mixture and engine seizure.

Rotary-valve lubrication also changes: 1985–1988 models use a separate reservoir, while 1989 models draw oil from the injection-oil reservoir.

Electrical Tests and Wiring References

The diagnostic material connects starting, misfire, and low-power symptoms with component tests. Two-stroke pressure-testing coverage addresses crankcase leakage that a cylinder-compression check alone may miss.

Tool references include Bombardier ignition tester P/N 419 0033 00 and Nippondenso CDI checker P/N 419 0084 00. Basic resistance checks use an ohmmeter; complete ignition testing calls for the specified test equipment.

Three full-page wiring diagrams separate the 1985–1986 MX/MX (H/A)/Plus, 1987 MX/MX LT/Plus, and 1988–1989 MX/MX LT/Plus/Plus LT/Mach I groups.

Sheave, Brake and Suspension Differences

Primary-sheave procedures distinguish the 1985–1986 MX/MX (H/A) assembly from the 1986 Plus/all 1987-on assembly. Tool callouts include crankshaft locking tool P/N 420 8766 40 and pulley alignment bar P/N 529 0071 00.

Brake illustrations separate the 1985 and 1986-on assemblies. Drive-axle coverage includes a Mach I-specific view, sprocket synchronization, chaincase alignment, and axial-play adjustment.

Suspension exploded views identify the different assemblies. Shock coverage includes spring removal, inspection, and replacement; internal damper-housing disassembly is excluded. These repair views support assembly work rather than serving as a dedicated parts catalog.

Maintenance, Storage and Workshop Precautions

Maintenance runs from pre-ride and break-in checks through periodic tune-up, recoil-starter overhaul, storage preparation, and return-to-service inspection. Quick Reference Data and chapter-end tables provide component-specific torque, capacities, wear limits, electrical test values, and setup specifications.

Electrical-output testing, fuel handling, compressed clutch or shock springs, and running-track checks carry system-specific safety warnings.

Examples of Float-Height and Rotary-Valve Data

Float-height tables specify 22–24 mm for VM34 carburetors, 16–18 mm for VM38 units, and 17–19 mm for VM40 units. These dimensions apply to the inverted-carburetor check, measured between the float arm and bowl-gasket surface without compressing the needle’s spring-loaded plunger.

The rotary-valve timing table lists the 1989 Mach I opening at 140° BTDC and closing at 61° ATDC, illustrating the model-specific timing data supplied alongside the inspection and installation procedures.