Scott Bonnar Model 65 — Maintenance Instructions & Parts List

Maintenance instructions and the complete parts list for the Scott Bonnar Model 65 in 20, 24 and 30 inch widths — how to remove and reverse the cutter, set the clutch gap, adjust the three chains and align the drum, followed by every part number with its cutting width.

• ModelsModel 65 in 20″, 24″ and 30″ (Honda G42 / G65 engines)
• Pages13
• Publication1942496

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The full maintenance instructions and parts list for the Scott Bonnar Model 65, publication 1942496 — a later Rover-era machine fitted with a Honda engine, built in 20″, 24″ and 30″ cutting widths.

Front roller

The height of cut of the mower is controlled by the adjustment of the front roller. The mower cuts lower if the front roller is raised, or alternatively the mower cuts higher if the front roller is lowered.

To adjust the roller, slightly loosen the bolts holding the roller scraper bar (1) Fig. 1. Adjust to required position. After the desired position has been obtained, tighten the bolts. For easy alignment notches are provided at each end.

Front roller scraper

The scraper is adjustable by loosening the holding screws (2) Fig. 1 and adjusting the blade to desired gap between scraper and roller.

Deflector

For cutting some grasses, the deflection into the grassbox can be improved by altering the deflector. To adjust, slightly loosen the adjustment set screws (3) Fig. 1 and by moving the deflector plate upwards, the grass throw will be higher and longer, or downwards and the grass throw will be lower and shorter. After adjustment retighten set screws.

Cutter

The bottom blade is fixed and adjustment for wear, or other reasons is confined to the cutter.

To adjust the cutter loosen the clamping bolts (4) Fig. 1 at each side. Turn adjusting nuts (5) Fig. 1 clockwise to lower the cutter on to the bottom blade. Retighten the two clamping bolts.

The cutter should be adjusted to bear lightly on the bottom blade along its full width. If the cutter rubs harshly on the bottom blade there will be excessive wear of both cutter blades and bottom blade, and an unnecessarily heavy load on the power unit. Excessive wear is also experienced if cutter is left running dry i.e. not cutting grass.

Cutter / sole plate assembly

The cutter and soleplate is one assembly and can only be removed as a unit.

1. Remove the deflector by unscrewing the adjustment set screws (3) Fig. 1. Pull the deflector upwards and forward. Spring clips are holding the bottom end to the soleplate.
2. Remove the chain cover (3 screws).
3. Remove cutter chain.
4. Remove cutter sprocket. Note, left-hand thread.
5. Finally remove the cutter clamping bolt (4) Fig. 2 and the two soleplate bolts (6) Fig. 2 at each side of the machine.

The whole assembly of cutter and soleplate/bottom blade is then free to drop out of the machine.

To remove the cutter from the above assembly the following procedure is to be used:

1. Remove the Cutter Bearing Housing Pivot Screws (7) Fig. 4 (5/16 A/F Allen key).
2. Remove cutter adjusting nuts, washers and spacer tubes (8) Fig. 4.
3. Cutter is now free from soleplate assembly.
4. Remove Bearing Housings (9) Fig. 4 from cutter. Ensure that the Bearing Housings remain in the same L.H. and R.H. position as the grease nipples otherwise will appear on the underside of the Housing.
5. Remove R.H. Bearing Nut. Note, left-hand thread.

Reversing the cutter

In time the cutting edge of the cutting cylinder becomes dull and a feature of this machine is that the cutter may be easily removed as described above, reversed end for end and replaced. This provides a new keen cutting edge. If the bottom blade is badly worn, this should be replaced at the same time.

To replace the cutter/soleplate assy. to the machine place the assembly directly below its final position and lower the machine onto the assembly. The holes for the screws are then easily lined up.

Cutter and drum clutch

The clutches are of a lined conical design and are adjustable for wear after a prolonged period of use. At the first sign of clutch slip stop using the mower and adjust the clutch. If the clutch is allowed to slip it will wear rapidly and could require relining.

To adjust a slipping clutch, determine if the spacing washer (10) Fig. 3 and ramp (11) Fig. 3 are clear of each other in engaged position. This gap is most important and must be greater than .015″. To reinstate the gap, remove the pivot (12) Fig. 3 from the ramp and screw the pivot towards the end of the control rod thus lengthening the action. Replace the pivot to the ramp.

Chain transmission

The three chains — engine shaft to countershaft (13) Fig. 3, countershaft to drum (14) Fig. 3 and engine shaft to cutter (15) Fig. 3 — are all provided with chain adjusters (16) Fig. 3. The chains should never be adjusted tightly, there should be about half an inch movement. It is advisable to leave slightly more slackness on the cutter chain to allow for cutter adjustment without having to adjust the chain.

Drum and components

The drums are manufactured from steel tubes with welded ends. The bearings and differential are greased at assembly and do not require any further attention. However, when the drums are dismantled for service they should be regreased.

On the right hand side of the machine provision is made to adjust the drum to be on same plane as the Cutter/Soleplate.

To check and adjust the drum, lay the machine on its handle with the drum on an even surface. From a front centre position of the machine, line up by eye the underside of the front roller and the cutting edge of the bottom blade. If they are not parallel, some adjustment has to be done to one end of the front roller. Now, line up the front roller with the drum.

If out of adjustment, loosen lightly the drum bearing housing bolts. Adjust to a parallel position on the adjuster (17) Fig. 2 and retighten the bolts and adjustment nuts.

Grease and oil lubrication

The following points require grease lubrication:

1. Front Roller Bearings (A).
2. Cutter Bearings (B).
3. Countershaft Bearing (both ends) (C).
4. Engine shaft Bearing (at side frame end only) (D).
5. Chains (smear lightly with grease) (13, 14, 15).

The following points require oil lubrication:

1. Clutch Ramps (E).
2. Clutch Lever Pivots (F).
3. Clutch Handles.
4. Clutch Inner Cones (20″ only).

Parts list

The printed list carries separate 20″, 24″ and 30″ columns. Those are combined into the Fits column below — for size-specific parts the width is already given in the description, and “All sizes” means the part is common to all three machines.

Illustration nos. 1–30 — frame, front roller, scraper and cutter

Illustration nos. 31–53 — soleplate, bottom blade, deflector and drums

Illustration nos. 54–92 — drum bearings, countershaft and clutch cones

Illustration nos. 93–130 — clutches, engine shaft, chains and handle

Illustration nos. 131–165 — grassbox, throttle, engine and guards

Transcribed from Scott Bonnar publication 1942496. The scanned pages in the viewer above are the authoritative source — if a number matters for an order, check it against the scan. Illustration numbers 111 and 115 are not used in the original. Rows marked NI are listed as “not illustrated”.

Engines: the 30″ machine was fitted with a Honda G65 HD (part 6280066) and the 20″ and 24″ machines with a Honda G42 HD (part 6280082) — useful to know, since Honda engine parts are far easier to source today than Scott Bonnar ones.

Warranty: the back page carries the standard Rover Scott Bonnar warranty — twelve months to the original purchaser, three months for other than domestic use, with transport costs borne by the purchaser and routine adjustments excluded. It is reproduced in the viewer above and is of historical interest only; it confers no rights today.