The factory operating and maintenance instructions for the Scott Bonnar 14-inch Bonmow — a two-stroke that runs on a 16:1 petrol-oil mixture, not straight petrol. Covers cold and hot starting, cutter setting, drum clutch, chain adjustment and every lubrication point, keyed to the numbered reference photograph.
- ModelsModel 19 Bonmow, 14″ petrol reel mower (two-stroke)
- Pages4
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Full text of this manual
A full transcription of the operating and maintenance instructions for the Scott Bonnar 14″ Bonmow petrol mower.
Before using this machine for the first time it will benefit you if you read these instructions thoroughly.
The bracketed numbers below — (1), (2), (3) and so on — refer to the callouts on the reference photograph, which is page 2 in the viewer above.
Important: this is a two-stroke. The Bonmow runs on a petrol–oil mixture, not straight petrol. Running it on unmixed fuel will destroy the engine. See the fuel note below.
Starting and operating instructions
To start when cold
- Fill tank with correct petrol-oil mixture, 16 parts petrol to one part Castrol XL oil, i.e., ½ point [sic — pint] of oil to one gallon of petrol. Do not use super-grade fuel. Mix in separate container — measure it, don’t guess.
- Pull fuel tap underneath tank (11) to “ON” position.
- Open throttle lever slightly.
- Close choke at top of snorkel tube.
- Depress carburettor tickler (12) and stop as soon as fuel starts to drip. There is no need to continue once the carburettor has been flooded, for fuel will only run to waste. It is suggested that this operation take place off your lawn, as petrol will kill the growth.
- Stand behind the machine, grasp recoil starter handle, and give a brisk pull upwards. Immediately engine starts, half open choke and allow engine to warm. Choke should be fully open for normal running.
About that fuel ratio: the original reads “½ point”, which is a printing error for ½ pint. The arithmetic confirms it — there are eight pints to the imperial gallon, so half a pint of oil per gallon of petrol is the 16:1 mixture stated in the same sentence.
To start when hot
It is not necessary to use choke or carburettor tickler. Open throttle slightly, and pull starter rope.
To stop
Turn off the fuel tap, and allow engine to run until mixture in carburettor is exhausted.
Caution
Do not fill the fuel tank while the engine is running. Avoid spilling fuel on to a hot engine — this may cause an explosion and serious injury.
To propel the mower, gently squeeze the clutch. This engages the rear roller and the machine will move forward. It is not necessary to exert undue pressure on the clutch lever. The clutch can be “slipped” to vary the speed of advance for mowing around shrubs and in awkward corners.
Adjustment and maintenance instructions
Warning
When making adjustments to the cutter or chain, remove lead from sparkplug to avoid accidentally starting the engine.
Height of cut
This adjustment is made by means of the front roller holding brackets. To cut higher, loosen nuts (1) each side of the machine, and depress roller, using indicating marks on brackets and sideframes as a guide. To cut lower, reverse procedure.
When adjusting for low cutting, do not set mower so low that the weight of the machine is taken on the bottom blade instead of the front roller. This would affect cutting and also place excessive load on the power unit.
Cutter setting
The cutter is set correctly when it is lightly touching the bottom blade along its full length. Hard bearing or uneven setting causes excessive wear on cutting edges and also places undue load on the power unit.
To test the setting, tip the machine back, place a blade of lawn grass or piece of paper between cutting cylinder and bottom blade, and gently turn cutting cylinder by hand. If the cutter is set correctly, the grass or paper should be cleanly cut.
To adjust, loosen the two clamping nuts on each side of the machine (2), loosen long adjusting screw locknut (3), then with a screwdriver turn adjusting screw (4) clockwise to set cutting cylinder down harder on the bottom blade. To take the cutting cylinder further away from the bottom blade, turn the adjusting screw anti-clockwise, then hold screw steady with screwdriver and tighten locknut. Re-tighten all nuts when setting is correct.
Drum clutch
Adjustment will rarely be necessary. Should there be too much play in clutch lever, slacken 2 nuts (5), and screw in screws until leather clutch plate is pressed to drum end. Then unscrew each screw an equal amount until clutch plate is free. Hold screw and tighten locknut.
Chain adjustment
The chain from power unit to cutter is adjusted by loosening four nuts holding table to sideframes (6), sliding table backwards or forwards as required. Check chain tension by turning to two or three positions. Firmly tighten nuts.
Chains from cutter to rear drum are adjusted by loosening two nuts (7). Then by exerting slight pressure upwards on the sprocket plate nut (8) chains will be felt to tighten. After tightening holding nuts a slight slackness should be felt in each chain.
Deflector
For cutting some grasses the deflection into the grass-box can be improved by slightly bending the upper edge of the deflector plate (9) evenly across the full width. The last inch of this plate is left unfastened to deflector plate end expressly for this purpose. Bending upwards throws grass higher and longer; bending downwards throws grass lower and shorter.
Lubrication
- Cutter bearings, being ballraces, occasionally need a light oil. Turn the spring clip each side (10) and the oil holes will be exposed. Be sure to turn the clip back again so that the indentation in clip sits into hole.
- Front rollers — oil shaft and slide roller back and forth on shaft a few times, which will work oil along shaft.
- Chains — for good service chains should be occasionally cleaned with a solvent and oiled.
General
This mower is constructed of first-class materials, and will give longer and more efficient service if kept clean. After cutting and before putting machine away, wipe blades down with an oily rag.
Check nuts occasionally to see they are not slack.
To obtain the best results from your mower, the cutter should be sharpened and set at least once a season. This can be arranged through any of our branches or distributors.
When ordering spares, please quote the serial number of your mower.
Guarantee (as printed)
This machine has been manufactured under close supervision and to the highest standards, and all precautions which are usual and reasonable have been taken to secure excellence of materials and workmanship.
This Company undertakes to replace parts, free of charge, which fail through faulty materials or workmanship, within six months from date of purchase, provided such parts are returned to us, carriage paid, for examination.
The Company will not accept liability for any loss, damage or accident directly, indirectly or consequently suffered by the purchaser, operator or any other person or to property as a result of such faults whether due to defective materials or workmanship or otherwise.
This guarantee does not apply to defects, which in the opinion of the Company, are caused by accident, wear or tear, misuse, or neglect, including the use of incorrect fuel, or by interference with the construction of the machine as completed by the Manufacturers.
This guarantee extends only to the original purchaser from the Manufacturers or their authorised Agent.
This guarantee is reproduced for historical completeness only. It expired with the original purchaser decades ago and confers no rights today. The mention of “incorrect fuel” is a reminder of how seriously the two-stroke mixture was taken.
Sold throughout Australia by (as printed)
Scott Bonnar Aust. Pty. Ltd., manufactured by Scott Bonnar Limited, Australia.
- New South Wales: 357 Liverpool Road, Ashfield · Telephone UA 2266
- Victoria: 265 Huntingdale Rd., Huntingdale, S.E.12 · 744 1277
- South Australia: 21–25 Gouger Street, Adelaide · Telephone LA 2686
- Queensland: 27 Ipswich Rd., South Brisbane · Telephone 91 2677
- Tasmania: Principal Agent: R. McDougall, 303 Elizabeth Street, Hobart · Telephone B 1798
- Western Australia: Distributors: Sandovers Limited, Hay Street, Perth · BF 0131
Transcribed from the original Scott Bonnar 14″ Bonmow operating and maintenance instructions. The scanned pages in the viewer above are the authoritative source.