Gravely Convertible 7.6 Service Manual

Gravely Form No. 16188P1 (11-74), a photocopy of which was given to me by the late Arnold Belkins, proprietor of Belkins Tractor in Georgetown, MA, and an enthusiastic and knowlegable Gravely fan. Written for just about the last production of Gravely-engined units, this document is largely applicable to earlier Model Ls. In a few places I have hyper-linked in notes regarding my own experience working on Gravelys. In general, the spelling and punctuation are unchanged from the original. The text is complete, but because my copy is not original, I haven't given priority to trying to scan the half-tone illustrations. At some point I may get around to adding scans of the line drawings, though.

Another page of mine offers more general information on Gravely 2-wheel walking tractors .


This manual is designed to give servicemen an indepth service procedure for the Convertible 7.6 tractor, and as an aid in diagnosis and repair.

This manual cannot take the place of proper routine maintenance, care and adjustments.

Gravely reserves the right to change specifications, or design at any time without notice or incurring obligation.

LH means Left Hand, RH means Right Hand. Directions are given from the operator's position; that is, as you would stand behind the tractor.

Table Of Contents

Air Intake System 5
Lubrication 5
Fuel System 6
Electrical System 8
Governor 9
Cleaning 10
Engine Tests 10
Engine General Service 11
Fan 11
Engine Reconditioning 11
Cylinder Reconditioning 12
Transmission Trouble Analysis 18
Forward-Reverse 19
High-Low 20
Differential (2-Speed) 20
Differential (Std) 22
Specifications and Torques 23
Power Take Off 24
Starter Clutch 26

Air Intake System (pg. 5)

The importance of maintaining an air cleaner in proper condition cannot be over-emphasized! Dirt induced through improperly installed, improperly serviced or inadequate dry type elements, wears out more engines than does long hours of operation. Furthermore, operating with a clogged element causes a richer fuel mixture which can lead to formation of harmful sludge deposits. Always cover carburetor or air horn when air cleaner is removed for servicing.

Dry type air cleaner elements should be serviced only when required. Need for air cleaner service is evident by a sudden loss of power for no apparent reason.

To clean, remove element and tap lightly on a flat surface to remove loose dirt. Replace element if dirt does not drop off easily or if the element is damaged in any way. Also, replace element if there is any evidence of dirt on the inside surface of the element.

DO NOT wash dry elements in any liquid or attempt to blow dirt off with air hose as this will puncture the filter element.

Handle new element carefully - do not use if the gasket surfaces are bent, twisted or damaged in any way. Use only genuine Gravely elements. Use of other elements will void warranty. Not only must the proper element be used but it must be properly installed to prevent unfiltered air from entering the engine.

Install air cleaner assembly in this sequence on the air cleaner mounting bracket:

  1. Rubber gasket
  2. Air cleaner mounting base
  3. Element
  4. Air cleaner cover
  5. Rubber sealing washer
  6. Flat washer
  7. Wing nut

Be sure the element gasket surfaces fit tightly on the base and cover. The wing nut should be finger tight.

Note: The above describes the late side-mounted ring-type filter. Earlier Model Ls used a wet filter mounted ahead of the cylinder. I've found the latter a little less vulnerable to icing when blowing dry snow, but the intake air certainly is hotter in the summer.

Lubrication (pg. 5)

Oil capacity is 5 U. S. pints. Use API classification SC or SD oils.

Summer - SAE 30 or SAE 10W-30

Winter - (32F or below) SAE 10W or SAE 10W-30

Maintain at oil level at full mark on dipstick. Be sure tractor is level when checking oil.

Oil Changes

Change the oil after the initial eight hours of operation. Then change the oil every 40 hours under normal conditions, oftener under dusty conditons and/or periods of extended operation.

Drain oil by removing the oil drain plug, the bottom bolt on the L. H. axle housing.

Be sure oil drain washer is in place when replacing the bolt.

Oil Filter

Under normal conditions, change the oil filter every 80 hours, however, under extremely dusty conditions and/or extended operation under heavy load, change the oil filter every 40 hours.

The oil filter must be installed by hand. Install the filter following the instructions printed on the filter.

Periodic oiling of all linkage pivot points aids operation.

Fuel System (pg. 6)

A. Adjustment

  1. Screw the main jet adjustment needle (a brass T-needle) in until it is snug. Do not force or screw it tightly.
  2. Back off the main jet adjustment needle 1 1/2 turns
  3. Start the engine and open the throttle halfway. After the engine warms up, begin screwing the needle, slowly. As soon as the engine begins to slow down, stop and back the needle off until the engine picks up speed.
  4. Screw the idle air jet adjustment needle all the way in; then back off one turn. Start the engine and allow it to idle. Screw the needle in until the engine begins to run rough. Then back the needle off until engine runs smooth.


The fuel supply system is made up of the threaded fuel inlet, the fuel valve seat, fuel valve needle, float and fuel bowl.

The fuel supply line is connected to the threaded inlet. The fuel travels through the fuel valve seat and passes around the fuel valve and into the fuel bowl. The level of fuel in the fuel chamber is regulated by the fload through its control of the fuel valve. The fuel valve does not open and close alternately, but assumes an opening, regulated by the float, sufficient to maintain a proper level in the fuel chamber equal to the demand of the engine according to its speed and load.

The inside bowl vent as illustrated by the passage originating in the air intake and continuaing through to the fuel bowl, is a method of venting the fuel bowl to maintain proper air fuel mixtures even though the air cleaner may become restricted. The balancing passage is frequently referred to as an "inside bowl vent".


The idle system consists of two idle discharge holes, idle air passage, idle adjusting needle, idle jet and fuel pick-up passage.

The fuel for idle is supplied through the main jet to a well directly below the main discharge jet. The pick-up passage is connected to the well by a restricted drilling at the bottom of this passage. The fuel travels through this channel to the idle jet calibration. The air for the idle mixture originates back of (or from behind) the main venturi. The position of the idle adjusting needle (normally one turn from its seat) in this passage controls the suction of the idle jet and thereby idle mixture. Turning the needle in closer to its seat results in a greater suction with a smaller amount of air and therefore a richer mixture. Turning the needle out away from its seat increases the amount of air and reduces the suction, and a leaner mixture is delivered. The fuel is atomised and mixed with the air in the passage leading to the discharge holes and enters the air stream at this point.


The high speed system controls the fuel mixture at part throttle speeds and a wide open throttle. This systems consists of a venturi, controlling the maximum volume of air admitted into the engine; the main jet, which regulates the flow of fuel from the float chamber to the main discharge jet; the well vent, which maintains uniform mixture ratio under changing suction and engine speeds; and a main discharge jet, which delivers the fuel into the air stream.

The main jet controls the fuel delivery during the part throttle range from about one-quarter to full throttle opening. A main jet adjustment permits a limited control of the main jet fuel. Ordinarily an adjustment of 1 1/2 turns from its seat will give proper mixture. To maintain a proper mixture ratio a small amount of air is admitted through the well vent into the discharge jet through the air bleed holes in the discharge jet at a point below the level of fuel in the metering well.


At high speeds the fuel flows from the fuel chamber through the main jet and into the main discharge jet where it is mixed with air admitted by the well vent, and the air-fuel mixture is then discharged into the air stream of the carburetor.

The choke system consists of a valve mounted on a shaft located in the air entrance and operated externally by a lever mounted on the shaft. The choke valve is used to restrict the air entering the carburetor. This increases the suction on the jets when starting the engine. The choke valve is of a "Semi_Automatic" type, having a poppet valve incorporated in its design, which is controlled by a spring.

The poppet valve opens automatically when the engine starts and admits air to avoid over-choking or flooding of the engine. The mixture required at starting is considerably richer than that needed to develop power at normal temperatures. As the engine fires and speed and suction are increased, the mixture ratio must be rapidly reduced. This change is accomplished through adjustment of the choke valve and the automatic opening of the poppet valve to admit more air when the engine fires.