1978 John Deere Spitfire 340 Snowmobile Technical Manual (TM-1191)

John Deere Technical Manual TM-1191 covers the 1978–1980 Spitfire 340, including J34AG, J34AH, and J34AJ configurations. The July 1979 publication includes revised electrical pages dated November 1979.

• Engine diagnosis and repair: Spark and compression tests, engine removal, crankcase disassembly, outer crankshaft bearing replacement, pressure testing, and separate Kohler and Fireburst recoil starter procedures.

• Mikuni carburetors: Slide-valve and butterfly carburetor disassembly, cleaning, float adjustment, choke and throttle-cable settings, plus altitude charts.

• Ignition and lighting: Engine-specific CDI tests, ignition timing, pulser and exciter coil replacement, alternator and regulator diagnosis, switch testing, and wiring diagrams.

• Power train: Comet 94C drive sheave repair, driven-sheave bushing replacement and spring pretensioning, drive-belt alignment, and drive-shaft service.

• Mechanical disk brakes: Separate removal, inspection, assembly, and adjustment procedures for serial numbers 80,001–95,000 and 95,001 onward.

• Suspension and steering: Slide-suspension removal, wear-bar and rear-idler replacement, track repairs and tensioning, ski alignment, and steering-bushing replacement.

• Service references: Tune-up guidance, troubleshooting charts, component specifications and torque tables, plus illustrated essential and convenience service tools.

This manual is suited to mechanics and experienced owners who can use precision measuring tools and follow electrical test procedures with the specified equipment.

Kohler and Fireburst Engine Repair

Both the Kohler K340-2FA and John Deere Fireburst TB340A have separate disassembly, inspection, and assembly instructions. Cylinder-bore tolerances, crankshaft runout limits, and piston-ring end gaps accompany the inspection procedures, with engine cross-section drawings and recoil-starter assembly views.

Chrome-plated cylinders are specified for replacement when out of tolerance; honing and reboring are excluded. Inner crankshaft bearings and seals are serviced with the complete crankshaft assembly, while outer bearings and seals have replacement procedures.

The Kohler flywheel instructions warn that tightening its retaining nut with an impact wrench can damage the flywheel or engine.

Mikuni Carburetors and Fuel Delivery

Separate slide-valve and butterfly sections include Float System cutaways and float-level adjustment illustrations. The butterfly-carburetor altitude charts distinguish machines through serial 120,000 from 120,001 onward, with settings grouped by temperature and elevation.

Fuel-pump checks, pickup-screen cleaning, and fuel-tank and filter service are covered separately. The pump is treated as a replacement unit if cleaning does not restore operation.

CDI Testing and Wiring Diagrams

The Electrical System wiring diagrams distinguish the layouts through serial 120,000 and from 120,001 onward. Kohler Nippondenso and Fireburst Kokusan ignition systems have different test routines.

JDM-74 tester procedures and Kohler ohmmeter charts help isolate charging-coil, trigger-circuit, CDI-unit, and ignition-coil faults before components are replaced. The CDI sections warn that test-light continuity checks can destroy the ignition system.

Observe the manual’s precautions for ignition shock, fuel handling, and spring-loaded recoil starter components.

Clutch Alignment, Track Repairs, and Steering

Clutch alignment uses JDM-107 for Kohler-powered machines and JDG-47 for Fireburst-powered machines. The corresponding belt specifications and altitude clutching charts help match the setup to the machine after engine or clutch service.

Exploded views of the slide suspension and skis and steering support component identification. Track-damage analysis distinguishes excessive tension, loose-track operation, and impact damage, alongside procedures for replacing individual grouser bars.

Ski spindles for serial 120,001 onward cannot be fitted to earlier machines. Hood, tunnel, and pan repairs are outside this manual’s coverage.

Examples of Engine Inspection and Ignition Data

These examples are a small selection of the engine inspection and electrical test data in the manual.

For the documented compression test with the choke off and throttle open, the Kohler K340-2FA reference range is 90–110 psi. The Fireburst TB340A range is 110–130 psi.

Fireburst connecting-rod side clearance is listed at 0.0157–0.0197 inches for new parts. In the Kohler ignition section, the 160–200-ohm resistance range applies specifically to the L1 capacitor charging coil.

PDF Navigation, Readability, and Page Count

Text search and diagram detail: Embedded bookmarks cover the contents, main sections, and wiring-diagram entry. Text search is limited by substantial OCR errors; the opening contents page has no searchable text. Small wiring labels require enlargement, and some labels on PDF p. 74 remain faint and difficult to read.

One printable, English-language PDF contains 145 pages: two opening pages for the contents and introduction, followed by 143 section pages. The revised electrical pages are already included in this total.