This article is largely reproduced from an original Rosebery manual which I was lucky enough to find in a country junk shop. There really is not that much to owning a Rosebery, but I'm sure people will find this book as useful as I did when the Rosebery is their first baby!

Thanks to Glen Harris these instructions are also available as a PDF


2, 3, 4 AND 6 H.P. TYPE  C



Each engine is carefully built, thoroughly tested and rigidly inspected, and the engine leaves our Works in first-class running condition. Therefore, leave the adjustments as they are set at the factory. Read the instructions, and be sure you understand the operation of each part.







When the engine is installed as a stationary engine in a permanent location, set the engine on 0 good concrete foundation, and see that the engine is set perfectly level. Where the ground is soft, make the base of the foundation larger than shown, Fig. 1, page 3, for 2 and 3 H.P. engines, or Fig. 2, page 4, for 4 and 6 H.P. engines. A solid foundation adds much to the successful operation of the engine.

In selecting a place for the engine foundation, be sure to allow -plenty of room, especially around the starting handle. The situation should be free from dust and moisture.

For safety, a good plan is to install the engine so that the belt pulley is near the wall. If the engine is of the tank-cooled type, remember to leave room for the cooling water tank, and have it placed so that the connecting pipes can be short and reasonably straight. The engine may be installed on wood skids, provided the engine is set level and the skids securely anchored. If bolted to the floor, be sure that the floor is well supported.

The most satisfactory belt drive is obtained by arranging the situation of the engine with respect to the driven machine so that the slack side of the belt is on top.


The correct size of the cooling water tank must be determined after considering the nature of the work which the engine has to do. For intermittent work 12 gallons per horsepower is sufficient, while 30 or more gallons per horse-power should be allowed when the engine is required to run for long periods. The piping to the cooling tank should be as short and direct as possible. All unnecessary bends should be eliminated. The lower connection should slope upwards from the bottom opening in the tank to the opening on the cylinder, and the upper connection should slope upwards from the cylinder head to the upper opening in the tank.

On no account use solid iron pipe oil the way from the tank to the engine, because if this is done a very small amount of vibration will in time tear the connections from the cooling tank or engine. Suitable bends or elbows should be screwed into the openings in the tank and engine so as to point in the right direction. Short pieces of pipe should be screwed into these, and rubber hose used to make the connections between .the pipes.

In order to avoid waste of water when the engine cylinder is drained, it is advisable to include either a three-way cock, or any ordinary cock together with a tee, with a plug in the third opening in the lower connection, close to the tank. When the cylinder is to be drained, turn the cock so as to shut off the water from the bottom of the tank, and the water in the cylinder jacket will escape through the third opening in the cock, or through the tee if the plug in the third opening is removed. With this arrangement, only the water above the upper tank connection is wasted. Never use dirty water or hard water as it will leave a deposit in the water passages in the engine.

Occasionally clean out the whole of the cooling water system and carefully examine the rubber hose connections to see that they are not frayed or likely to prevent the free circulation of the water.


In piping the exhaust from the engine, always use as straight a pipe as possible. If the exhaust passes through a wall, place the silencer on the outside, and place a pipe union

Always state Engine and Part Number when ordering Spares


14 ¼"
6 ½"
14 ¼"
6 ½"
11 11/16"
4 5/8"
14 11/16"
4 5/8"

right near the cylinder. If the exhaust pipe is longer than ten feet, then use a size larger pipe.

Remember, for the best results the exhaust should reach the open air within the shortest distance possible, because long exhaust pipes invariably reduce the power of the engine.

The silencer supplied with the engine is very efficient, and causes very little back pressure.

Occasionally remove silencer and thoroughly remove all carbon deposits. Failure to do this will eventually cause a considerable loss in power from the engine


These engines are equipped with a special petrol-kerosine vaporiser, enabling them to be operated as petrol or kerosine engines at the option of the user.

Should it be desired to operate the engine as a petrol engine, the main tank on the engine should be filled with petrol, and no use need be made of the small bowl or reservoir on the side of the' vaporiser. The throttle valve on the side of the small valve should be screwed hard to the right and kept in this position.

The engine will now start and function as an ordinary petrol engine.

If the engine is to be operated on kerosine, see that the main tank is filled with power kerosine and the small bowl on the side of the vaporiser with petrol.

The engine should not be operated on kerosine if the load is rapidly fluctuating or is not reasonably heavy. The engine should not be allowed to idle except for very short intervals when running on kerosine. Very, light loads or rapidly fluctuating loads interfere seriously with the correct vaporisation of kerosine and will cause rapid dilution of the lubricating oil.

Always use a good grade of power kerosine. Lighting kerosine is not intended to be used as an engine fuel and should never be used.

The following instructions for starting the engine should be observed.


  1. Unscrew the breather valve from the governor housing and fill the sump to the correct level by pouring oil in the breather. Remove the dip stick and see that the oil is up to the high level mark, H. The oil level should never get below the low level mark. L. Never remove the dip stick when the engine is running.
  2. Put a few drops of oil on each of the joints of the  governor mechanism.
  3. See that water level, in the case of tank-cooled engines, is well above the upper connection in the tank, and in the case of hopper-cooled engines, is well above the cylinder head. The water must never be allowed to fall below these levels. In the case of tank-cooled engines with a cock connected into the lower cooling tank connection, make certain that the cock is turned full on so that the water con circulate freely.
  4. See that there is plenty of fuel in the tank.


  1. Study all the preceding instructions carefully, and also  make sure that you know how to stop the engine.
  2. If the engine is to be operated on petrol, screw  the throttle valve on the vaporiser to mark 1.If the engine is to be operated on kerosine, screw the throttle valve on the vaporiser right in (as for as possible to the right) so as to shut off the kerosine supply. Open throttle valve on petrol bowl about one-quarter of a turn until mark 1 is on top. When the engine is very cold, starting may be assisted by holding a finger of the left hand on lop of the auxiliary air valve stem- so as to almost prevent air entering whilst cranking the engine. When doing this be careful not to flood the vaporiser.
  3. Turn the flywheel backwards, that is in the anti-clockwise direction, until the compression in the cylinder is felt. This will enable you to make a full turn on the starting handle before coming on to the compression stroke.
  4. Attach the starting handle to the crankshaft on the governor side, and give the engine a few quick turns in a clockwise direction.
  5. Immediately the engine starts, remove the left hand  from the auxiliary air valve.
  6. Running as a petrol engine. As the engine  warms up, slowly turn the throttle valve towards Mark 2. It is always advisable to run with the throttle valve turned as for as possible away from 1 without causing the engine to miss of lose power. Running as a kerosine engine. -- After the engine has been running for a few Minutes, and when the inlet and exhaust manifold have become heated, gradually close the petrol throttle valve and at the some time open the kerosine throttle valve. As the engine continues to warm up, dose the petrol throttle valve off tight and turn the kerosine throttle valve towards the closed position as for as possible without Causing the engine to miss or stop.

Important: Always make sure that the engine is well heated up before running on kerosine. In very cold weather, particularly with tank-cooled engines, it may be necessary to fill the petrol bowl more than once.


Screw down the throttle valve away from 1 and through 2 as far as it will go, without straining it.


The following suggestions may be of assistance in locating and remedying engine troubles. They are mode to enable emergency repairs to be carried out. In any case Ahere serious troubles occur, we suggest that a competent mechanic be employed.

(a) Engine Will Not Start, or Starts and Stops.

  1. Examine fuel tank and see that there is ample fuel of  good grade.
  2. Test the ignition system, as described under ignition  page 13.
  3. Too weal, a mixture. Turn the throttle valve further in direction 1, or when the engine is very cold hold a finger on top of the auxiliary air valve stem so as to limit the air supply until the engine warms up.
  4. A weak mixture may also be caused by air leaks at the vaporiser or auxiliary air valve flange gaskets. Therefore, examine these points and tighten up the nuts holding these parts in position.
  5. Another cause of a weak mixture is dirt or water in the  vaporiser jet or in the check valve and strainer. Remove these parts and clean thoroughly. Also examine the check valve and see that it is seating properly and does not leak.
  6. Too rich a mixture. This is likely to happen if the engine is warm, and if the air supply has been choked too much by hand or if the throttle valve is turned too far towards 1. To overcome this, turn the throttle valve so as to close it, remove the spark plug, and crank the engine for a while in order to clear the overrich mixture from the cylinder.
  7. Read the paragraph on the vaporiser on page 15, and see that the auxiliary air valve spring is properly adjusted. Incorrect adjustment may cause too weak or too rich a mixture.

(b) Engine Runs, but Heats or Knocks

  1. Insufficient water in the tank or hopper. Fill to the  proper level.
  2. Cock in the lower tank connection turned off or partially off. This cock should always be in the wide open position.
  3. Rubber connecting hoses frayed and blocking pipes.  Replace with new hoses and clean out pipes.
  4. Pipes or water passages in cylinder dirty. Clean out  all the pipes and passages, and also the water tank.
  5. Oil supply low or wrong grade of oil. Follow the instruc tions.
  6. Wrong type of spark plug. Always use the some type  of plug as originally supplied with the engine.
  7. Too rich a mixture. Turn the throttle valve as for as possible away from mark 1. Too rich a mixture causes block smoke to come from the exhaust.
  8. Too weak a mixture. Turn the throttle valve slightly  towards 1.
  9. Muffler clogged. Remove it and clean out with a piece  of wire.
  10. Excessive carbon deposits. Decarbonise, as described  under paragraph headed, Removing Carbon, page 16 ignition retarded or advanced too far. Check the timing of the magneto. See paragraph headed, Timing the Magneto, page 13.
  11. Another kind of knock, quite distinct from the noise caused by the above, is due to loose bearings. This knock should not be heard until the engine has seen long service. Never run with loose bearings. They should be adjusted immediately.

(c) Engine Misfires.

  1. Engine not warmed up. If possible, always allow the engine to run for a few minutes without load when first started.
  2. Oiled-up or defective spark plug. Clean thoroughly  and adjust the points or fit new plug.
  3. Valve tappets set too close. Examine and reset to the  correct clearance. See page 17.
  4. Dirt or water in the fuel, vaporiser, or check valve and strainer. Thoroughly clean as described in paragraph, page 15, on Vaporiser.
  5. Magneto contact-breaker points dirty or sticking. Clean and adjust, as described in the Magneto Instruction Book.
  6. Air valve or throttle valve not correctly adjusted. See  paragraph on Vaporiser, page 15.

(d) Engine Locks Power

All the points under the previous paragraphs (b) and (c) should be examined. In addition, the valves may require regrinding. In the case of an engine that has seen long service, new piston rings may be required, or in extreme cases, the cylinder should be reground and a new piston fitted.

(e) Engine Races

  1. See that the governor mechanism is working freely and is not catching or fouling the high-tension cable, or any other part of the engine.
  2. Examine the governor valve stop-screw on the vaporiser, and see that it is not screwed in so for that the throttle cannot close sufficiently to prevent the engine from racing.
  3. Read the section on the Governor, page 14, and check  the adjustments.

(f) Engine Stops Suddenly

  1. Fuel tank empty.
  2. Examine the whole of the ignition system.
  3. Choked strainer in the fuel tank or jet in the vaporiser,  or fuel pipes.' Clean thoroughly.
  4. Vent hole in the filler cop on the fuel tank clogged.  Always see that the vent hole is clean.
  5. Sudden increase in the load, making the total load too heavy for the engine to pull. Examine the driven machine, and see that it is working freely and that it is not doing more work than usual.

In addition, anything that will cause the engine to run badly may eventually cause the engine to stop.


The lubricating system used on this engine is practically infallible, provided that the correct grade of lubricating oil is used and the following instructions are carried out. For best results use SINGLE SHELL MOTOR OIL S.A.E. 30. The engine uses very little lubricating oil, and it is very poor economy to use inferior oil.

Referring to the sectional drawing, page 18, it will be seen that the base is arranged so as to form a sump containing a sufficient supply of oil to lubricate the engine- for several days.

A dipper on the connecting rod provides an efficient splash system of lubrication. Oil is splashed from the sump to all parts of the engine. The level of the oil in the base is shown on a dip stick placed just below the magneto.

To fill the sump: Unscrew the breather valve from the governor housing and fill the sump to the correct level by pouring oil into the opening.

Care should be taken when filling, that the oil is not allowed to rise above the high mark on the dip stick.

Never permit the oil level in the crankcase to get below the low level on the dip stick.

Always state Engine and Part Number when ordering Spares

Every day, before starting the engine, remove the dip stick and see that the oil is up to the correct level. Keep the oil at the correct level at all times.

The breather should always be screwed on again after filling the base with oil and should not be removed while the engine is running.


Even the best of oil becomes diluted in service, due to absorption of the fuel. This happens very rapidly if an overrich mixture is supplied by the vaporiser.

The oil in the crankcase also becomes contaminated with particles of carbon flaking from inside the piston. It is, therefore, necessary to drain out the old oil and replenish with fresh oil at regular intervals.

To drain , remove the drain plug which will be found below the dip stick. Drain while the. engine is warm, and the oil is agitated, as it will then carry off the greater part of any loose sediment. Drain off the old crankcase oil after the first twenty hours of operation of a new engine, and then after each fifty hours of service.

If kerosine is being used as a fuel, change the oil after each thirty hours of service.

Do not flush with kerosine. If kerosine is used, some will be trapped in the troughs and oil pockets in the crankcase, diluting the fresh oil and impairing its lubricating qualities.

Draining the oil while warm will accomplish all that flushing with kerosine can do in the removal of sediment.

Finally, refill the crankcase with fresh oil to the proper level.

Occasionally, say, every six months, after draining the oil out of the crankcase, undo the four nuts on the crankcase

inspection cover and wipe out the base with a clean rag that will not leave any loose threads.


The majority of difficulties with lubrication will be avoided by following the foregoing instructions. In case of trouble, however, the following suggestions will be helpful.

Excessive oil consumption or oil pumping, as shown by the continual discharge of blue smoke from the exhaust, by excessive carbon deposits, or by spark plug fouling, may result from:

  1. Overfilling the crankcase. Never fill above the high  mark on the dip stick.
  2. Diluted oil. Follow the directions for changing the oil
  3. Use of incorrect oil. Follow the recommendations.
  4. Gummed-up oil scraper ring and drain holes. Remove the connecting rod and piston and clean the ring and oil drainholes with gasoline and a brush.
  5. Worn cylinders, pistons, or rings. The cylinders should be re-ground and new pistons and rings fitted as required. Do not on any account use a heavier oil, as no oil can take the place and perform the functions of metal that has worn away


A very efficient oil seal is provided on these engines to prevent oil throwing. Referring to cutaway view, pages 18, 19, it will be seen that the oil seals are placed just at the point of exit of the crankshaft from the engine.

To prevent oil throwing: Keep the engine clean. Follow the instructions given concerning care of the breather. If the engine is still throwing oil, renew the oil seals.


For maintenance of the magneto, see the separate Magneto Instruction Book.

Adjustment of Sparking Plug. - The plug electrodes. are bound to burn away slightly, and thus in time the gap increases. Occasionally examine and clean the points and also clean all sooty deposits from the centre of the plug. If necessary, adjust the gap between the electrodes to about twenty one-thousandths of an inch, or to about the thickness of an ordinary playing card.

The Detecting and Remedy of Ignition Faults. - Remove the sparking plug, and without disconnecting the high-tension cable, lay it on its side on the cylinder so that only the threaded part of the plug touches the metal, and observe if a spark occurs between the points when the engine. is cranked.

If a good spark occurs it may be assumed that the ignition system is in good order.

If no spark occurs, clean the plug thoroughly, and adjust the gap between the electrodes; then test again. If no spark shows, try a new plug. If this does not overcome the trouble, examine the high-tension cable from the magneto to the plug, and see that there are no signs of wear or cracking. For faults in the magneto, refer to the Magneto Instruction Book.

If the owner is still in any doubt or difficulty about his ignition system, he is strongly advised to consult the nearest magneto service station.

Timing the Magneto. - The magneto is correctly timed when fitted. If for any reason the timing has been disturbed and the magneto must be re-timed proceed as follows: Since the magneto is driven from the camshaft, it is first necessary to see that this is correctly timed. See Timing of Valves, page 16.

Remove the cover from the magneto contact breaker. Turn the flywheel until the word SPARK stamped on the flywheel is opposite the centre of the plug in the cylinder water jacket on 4 H.P. and 6 H.P., and on 2 H.P. and 3 H.P. opposite "C." The contact points should be just commencing to open. If this is not so, undo the set-screws holding the magneto to the engine and remove it. Slacken the nut which holds the magneto coupling on to the tapered magneto shaft. The coupling may then be turned on the shaft as much as required to correct the timing. Re-tighten the coupling nut and replace

the magneto and test the contact points again. Repeat, it necessary, until correct.


The governor is designed so that the engine can be set to run at any speed within its range.

The 2 H.P. engine will run at any speed between 750 and 1,100 r.p.m.

The 3 H.P. engine will run at any speed between 750 and 1,100 r.p.m.

The 4 H.P. engine will run at any speed between 600 and 900 r.p.m.

The 6 H.P. engine will run at any speed between 600 and 800 r.p.m.

The horse-power developed is proportional to the speed.

The speed con be varied by altering the tension on the speed regulator spring. To increase the speed, increase the tension, and to decrease the speed decrease the tension by turning the wing nut on the speed regulator rod.

If the engine races on light load and runs at the correct speed on full load , proceed as follows:

  1. See that the governor valve stop screw is not screwed in  too far.
  2. Attend to the adjustment of the governor link. To do this, pull the governor valve crank down as far as possible until it is stopped by the governor valve stop screw, and from that position measure the travel of the governor plunger marked 46, cutaway view, pages 18, 19, when the governor link is released. This should be I". Adjust the length of the governor link until this is correct.


The breather contains a valve which covers an opening in the governor housing cover.

Each time the piston descends in the cylinder any surplus air or vapours in the crankcase are expelled through this valve. On the up stroke of the piston a slight vacuum is caused in the crankcase because the breather valve has re

turned to its seat, and no air can pass it. This vacuum has the effect of preventing oil being sucked up past the piston or escaping along the crankshaft or through any of the joints, provided that they are reasonably tight. Each time the engine is started, see that the valve is working and has not stuck.

The movement of this valve is very small.

If oil escapes through the breather, examine the valve and see that it is working freely, and that it and the valve seat are quite clean.


The vaporiser is so designed that a small amount of air is admitted through a hole in the auxiliary air valve. This supply of air is not sufficient when the engine is running on load and a further supply is admitted through the auxiliary air valve. This valve thus serves the purpose of keeping the strength of the mixture of air and fuel correct, regardless of load.

The suction on the intake stroke draws the fuel from the tank. A check valve on the end of the fuel pipe near the tank prevents the fuel from running back during the interval between suction strokes, and thus maintains a constant level of fuel in the jet. A small strainer is attached to the bottom of the fuel tank.

The engine should run regularly when the throttle valve is set approximately on mark 2. Weather conditions, height above sea-level, etc., affect this setting slightly, so that the exact setting must be found by trial. If black smoke is emitted at the exhaust, it indicates that the mixture is too rich, and the throttle valve should be screwed in a little. If the valve is screwed down too far, the engine will lose power, and will slow down. By observing the governor valve crank and the exhaust, the throttle valve can be set to the best .position.

Smoke caused by excess fuel is block, whilst that caused by excess of lubricating oil is whitish.

if difficulty is experienced at starting, and it is ascertained that the ignition system is in order, see that the check valve at the end of the fuel pipe is not leaking owing to dirt on the seat.

Irregularities in operation may be caused by the jet being stopped up with dirt. Remove the jet and clean it with fine, soft wire.

The auxiliary air valve is correctly adjusted before the engine leaves the Works, and if the throttle valve is correctly adjusted the engine should fire evenly at any load. However, varying local conditions may necessitate slight alterations to get the best results. If the auxiliary air valve spring adjusting screw is turned down too for the engine will fire evenly at light load, but the mixture will be too rich at full load. If the screw is not down for enough, and the throttle is adjusted so that the mixture is correct at light load, the mixture will be too weak at full load.

Occasionally examine the small air vent in the fuel tank filler cop. This should always be kept clean. The fuel outlet pipe is arranged so that a little fuel is always left in the tank, so that water and dirt in the bottom of the tank will not be drown into the check valve and vaporiser.

Periodically remove the fuel tank and clean it thoroughly.


After the engine has been in service for some time, or preignition cannot be overcome at full load by cleaning out the water passages in the cylinder block, or the connections to the tank, the cylinder head should be removed and the carbon cleaned out of the combustion chamber and from the top of the piston, and the valves should be ground.

In taking off the head, take a blunt chisel and force up. under the edge of the head. Do not pry between the head and the gasket, or the gasket may be damaged.


Remove the valve tappet cover by undoing one wing nut.

When grinding the valves, use a fine valve-grinding com-^ pound. Take off the valve spring washers and drop the springs~

and slacken back the tappets so that the ends of the valve stems will not rest on them while grinding. Clean. the valves and seat thoroughly after grinding.

Replace the valve tappet cover. Never run the engine with the valve tappet cover removed.


The various timing gears are marked when the engine leaves the Works, but in case. the marks cannot be found, and

have not been marked before disassembly, the following information should be useful.

When the valves are correctly timed the exhaust valve should just be closing, and the inlet valve just opening, when the piston is at the top of its stroke.

Adjust the tappet screws until a thin visiting card (about 0.006") will slip between the valve stem and the tappet screw; then tighten up the locknut.


The camshaft runs on a floating camshaft spindle which is located at each end with camshaft buttons, which ore cupshaped stampings. These are held in place by means of a slight toper formed on them.

To remove the camshaft, one of these must be driven out by driving the other further in by means of a flat punch. When one button has been removed, the other may easily be driven out by driving from the other end.

To replace, put the camshaft back, taking care to get the timing correct. Replace the camshaft spindle, and top the camshaft buttons in at each end.


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