1978 John Deere Spitfire 340 Snowmobile Factory Service Manual (TM1191)

• Official John Deere OEM technical publication TM-1191 (July 1979 revision).
• Covers 1978–1980 Spitfire 340 snowmobile configurations, including J34AG, J34AH, and J34AJ variants.
• Comprehensive 145-page factory reference documenting specifications for Kohler K340 and John Deere Fireburst TB340 series engines.
• Features 48 exploded-view diagrams, 4 technical specification tables, and 12 electrical wiring schematics.

Component and System Documentation

Mechanics tackling a teardown or rebuild will find the detailed assembly and inspection data essential for the power train. This includes exact factory tolerances for the Comet 94C drive sheave, driven sheave, and the mechanical disk brake systems. The document logically breaks the snowmobile down into six primary service groups: General, Engine, Fuel System, Electrical System, Power Train, and Suspension. Need to verify engine components? It thoroughly covers both the Kohler K340-2FA and the John Deere Fireburst TB340A. You get precise cylinder bore tolerances. Crankshaft runout limits. Piston ring end gap requirements. This provides all the raw data required to verify parts are strictly within factory spec.

Specification Highlights

Having exact numbers at your fingertips prevents costly guesswork in the shop. Engine compression for the Spitfire 340 should read between 110 and 130 psi (758–890 kPa), while connecting rod side clearance is specified at 0.0157 to 0.0197 inches. For electrical troubleshooting, the primary charging coils require a magneto pick-up resistance of 160 to 200 ohms. Tuning for different elevations is straightforward thanks to altitude charts mapping Mikuni carburetor settings across various temperature ranges. Fastener torque values, like the 5 ft-lbs (6.8 Nm) required for stator screws, are clearly outlined. Working on vintage snowmobiles carries inherent risks due to aging mechanical and fuel systems, so professionals must always ensure safe shop practices and proper ventilation when inspecting these components.