- Details
- Category: Rigid Frame MAC Service Manual
- Hits: 1141
Driving Instructions
Always, before taking out the machine, or even starting the engine, make sure that it is ready for the road. See that there is a sufficient amount of fuel for the journey, and that there is enough oil in the oil tank and gearbox.
Before attempting to start up the engine make sure that the gears are in neutral (" free engine ") position. This can be found out by raising the clutch lever and pressing down on the foot-starter. If a gear is engaged the foot-starter will not go down freely but will cause the machine to run forward. To select neutral move gear pedal as required. The number of movements needed will depend on which gear is engaged, as the following explanation will show.
The gear control pedal operates a spring loaded spindle (in the gearbox) carrying a pawl that moves the cam plate one position at a time, and after each movement either up or down returns to its central position. If 1st(low) gear is in engagement and the pedal is pressed down as far as it will go, 2nd gear will be selected. A second pressure downwards on the pedal will give 3rd gear, and a third movement down will give 4th (top) gear. From 4th gear position three successive lifts of the pedal (moving it to its limit and releasing it each time) will select 1st speed. The neutral position is between 1st and 2nd gears. From 1st speed a half movement of the pedal downwards will be needed or from 2nd gear a half movement upwards. (See also note on page 4)¶
It must be remembered that in trying to select the gears one after another with the engine and machine at rest it is exceedingly unlikely that all four speeds will engage straight away without moving the gears by turning the engine or the rear wheel because, as often happens, the driving dogs which have to interlock will probably be opposite one another. In such a position forcing the lever will only cause damage. A slight movement of the machine either backwards or forwards will, however, alter the position of the dogs and allow engagement to take place.
A rider will very soon become accustomed to detecting whether engagement has taken place as a distinct " click " will be heard (just before the lever reaches the end of its travel) as the spring loaded indexing pawl snaps into the gear location notch in the edge of the cam plate. A novice is advised to select neutral from 1st gear position rather than from 2nd gear.
NOTE SPECIALLY. The pedal must be moved to the full extent of its travel when selecting a gear either up or down—half a movement only for neutral.
The pedal must not be stamped upon or forced. At the same time hesitant or half-hearted movement may not give engagement.
Therefore always move the pedal firmly and decisively till it stops. Keep the foot away from the pedal except when changing gear. Unless the lever can return freely the next gear will not engage.
To Start the Engine.
First open one of the fuel taps (preferably the right-hand one) by pressing in the hexagon knob. Lean the machine sharply over to the right side for about 20 seconds to flood the carburetter or depress the "Tickler." The "Tickler" is a small spring loaded button on the lid of the float chamber (Fig. 45). After a few seconds, whichever method is used fuel will be seen to seep out through a small hole in the side of the mixing chamber body. As soon as this occurs release the " tickler " or return the machine to the vertical. Do not flood excessively when cold. Do not flood at all when the engine is hot.
Turn the small throttle stop screw clockwise till the lug on the screw touches the side of the mixing chamber body (Fig. 45). This screw is fitted obliquely upwards in the side of the mixing chamber and has a small crossbar in the head to provide a convenient grip for the fingers. It holds the throttle valve slightly open in the best position for starting. Shut off the twist grip fully and if engine is cold close the air control lever. Set ignition lever about one-third advanced if old machine with manual control.
Now raise the exhaust valve by operating the small control lever on the handlebar. While holding this lever up press the footpiece of the starter slowly down. After a short distance the ratchet will be felt to engage the ratchet gear in the gear box when pressure should be continued to rotate the engine. When fully depressed release the footpiece, which will be returned to the top by its return spring. Repeat this operation a few times to fill the cylinder with combustible mixture, and to free the engine.
When this has been done release the exhaust lifter lever and press the footstarter down slowly as before. Resistance will now be encountered due to the compression of gas in the cylinder. When this is felt, raise the exhaust lifter lever and press the footpiece down slowly to the bottom.
Allow the footpiece to return to the top once more, move down to engage the ratchets and give it a sharp downward thrust without raising the exhaust lifter lever. This should rotate the engine fast enough for it to start. If it does not do so at the first attempt — Try again.
Notes on using the Footstarter.
It is very important not to kick sharply before the ratchet has engaged properly. It will be noticed that as the footpiece moves down, the ratchet is allowed to slide into the ratchet housing on the end cover due to the lug running off the disengaging cam formed at the end of the housing. It must be allowed to slide in properly, otherwise the ratchet will not engage properly, and damage will be caused to the teeth on the ratchet and ratchet gear. Do not hurry the operation—by being careful and deliberate time will be saved in the long run. Always release the footpiece as soon as the engine starts.
When the engine is running open the air control lever gradually. After a few moments the engine will accept the full air supply. Should the air not be opened soon enough the engine will fire irregularly, usually missing every other beat (eight stroking) and black smoke will issue from the silencer. Open the air fully immediately either of these symptoms is noticed.
When the engine is running. regularly with full air supply turn the throttle stop screw as far as it will go anti-clockwise (stop lug to the rear) to the correct setting for slow running and for starting when the engine is hot. Generally speaking, the " fast " position of the stop screw (that is with the lug forward) is only necessary for starting a cold engine.
Notes on Obstinacy in Starting.
During cold and damp weather the cause may be a damp or dirty high tension cable from the magneto to the sparking plug or the outside insulation of the plug may be coated with mud. This provides a path for the high tension current which " leaks " to " earth," diminishing the intensity of the spark at the plug points. Clean the affected parts with dry rag.
Over-rich Mixture
Caused by excessive flooding of the carburetter or of flooding when hot. Rectify by opening throttle and air controls fully and rotate engine sharply several times with the footstarter to clear the over-rich mixture. Turn off the fuel. Close throttle, leave air control full open and try again. If still unsuccessful take out sparking plug and clean internal insulation and firing points ; they will probably be " wet " with excess unvapourized fuel. Before replacing the sparking plug check the cap between the firing points (this should be .018" to .023") and reset if needed. Also rotate engine several times to clear out the rich mixture from the combustion chamber.
Provided the trouble is not of a more serious nature, necessitating workshop attention, the engine should start after this. Turn on the fuel after the engine starts.
When the Engine is Cold always allow a few minutes to elapse after starting for the oil to circulate before running it up to high speed. A fairly fast tick-over is about right. The circulation of the oil can be checked by taking off the cap from the oil tank, when oil will be observed running back into the tank from the pipe inside the neck of the tank. See also page 13.
Starting Away.
Having got the engine running, push up the prop stand on the left side of the machine. If folds backwards and upwards below the frame tube. This is very important. If left down it can be very dangerous.
Free the clutch by gripping the clutch lever and pulling it back into contact with the handlebar grip. Raise the gear pedal to engage first speed (see note page 4) The dogs should be felt or heard to engage. Release the pedal. If the dogs do not engage do not force the pedal but move the machine slightly backwards or forwards to alter the position of the dogs and try again. Alternatively, momentarily release the clutch lever with the gears in neutral and then make another attempt. Never in any circumstances move the gear pedal unless the clutch is freed first if the engine is running. Note specially that no amount of force will engage the dogs unless they are in such a position that they can interlock or mesh with one another. Having engaged first speed (low gear) by the upward movement of the control pedal release the clutch lever very gradually and at the same time open the throttle slightly when the drive will gradually be taken up and the machine will begin to move forward. When this occurs do not be in a hurry to release the clutch lever suddenly or the engine may stall. Continue to let it out slowly and at the same time increase the amount of throttle opening. Conversely, do not " race " the engine up to high speed without releasing the clutch lever. It cannot drive the machine at all until the clutch commences to grip. A good driver can always be picked out by his clutch work as he always gets away with the minimum amount of fuss and noise and does not race the engine excessively.
When well under way and at about 15 m.p.h. on the level free the clutch again and slightly close the throttle, pause about a second and then press down the gear pedal firmly until it stops, release the clutch again as this is done and open the throttle gradually. Take the foot off the gear pedal allowing it to return to mid position. Change up to third speed at about 25 m.p.h. by repeating the process, and when a speed of 35 m.p.h. is reached, change into top.
To change to a lower gear the procedure is similar except that the throttle should be left open and the pedal moved upwards as far as it will go. Three upward movements in succession from top will bring the gears back to first speed.
Bear in mind that a little practice is required in order to become proficient. Remember that the throttle should be closed when changing to a higher gear and the change made slowly, whilst a change to a lower gear should be made quickly with the throttle open. Never look down when changing gear. Keep looking at the road ahead. Never change gear with the heel.
The road speeds quoted are for a fully run in engine and are right for all general riding. Special conditions, as when starting on a gradient, may make it necessary to reach a higher road speed before changing up as of necessity some speed is lost as a change is made and if made too early the machine may be running too slowly for the engine to pull away properly by the time the higher gear is engaged.
To stop, close the throttle, and as the machine slows to about 15 m.p.h. free the clutch. Raise the gear pedal fully and release it twice in succession, and then raise it half way slowly until the pawl is felt to click into the neutral notch. Apply the brakes and release the clutch lever gradually. Never release it suddenly before it is certain that neutral has been found. When the machine is stationary close the fuel tap if the machine is not to be driven away at once, and raise the exhaust lifter lever to stop the engine.
Running in a New Engine.
A new machine requires to be driven with restraint until all working parts become thoroughly free or " bedded down " and will not give of its best until this has occurred and it is, as it is termed, " run in." It is a mistake to drive a new machine hard and give it too much " collar work " to do. Hard pulling (" slogging ") on a large throttle opening uphill must be avoided, and liberal use should be made of the gearbox so as to ease the load on the engine and allow it to run as lightly loaded as possible. A high road speed is not injurious and can in fact be beneficial if the speed is reached without opening the throttle wide and as this condition will often arise going down hill, we do not necessarily advise that the speed in top gear should be limited to any set speed. It has been found by experience that to run in a new engine at a fixed and regular speed is sometimes very unsatisfactory. Vary the speed as much as possible, but always run the engine lightly loaded, indulging in short, sharp bursts of speed occasionally. The speed and duration of these may be increased as the mileage reaches the 500 figure and after about 1,000 miles the engine should be properly run in.