(3) ;That the shoulder nut which screws out the body, and holds the rubber sleeve and plug in position is not screwed down too tightly, only finger tight is necessary, and best, otherwise the valve rubber is injured on the valve seating.

(4) ;That the body nut that bears against the wheel rim is tight against the rim, and so prevents the valve from moving in the rim.

The rubber sleeve when in position on the small plug should pass easily into the body, if not, clean out the body with a suitable twist-drill. When tyres are partly or otherwise removed from the wheel rims, it should be carefully watched that no dirt gets into the inside of cover, and that no tools are left therein, the latter event is not by any means an unknown occurrence.

No cycle repairs of any sort should be attempted over grass grown ground, if it can be possibly avoided, as if any small part be dropt into the grass, it generally is a very lengthy operation to find it again, before now petrol has been obtained, poured on the grass, a light applied, and search made among the ashes, and not always with success.

Pneumatic tyres should be pumped up as hard as the user can permit for comfort, this lengthens the tyre life considerably, and reduces the risk of punctures, although it may not add to the comfort of the rider over rough roads. The matter is of course a compromise between life of tyres as against comfort of riding, and as an added inducement to pump tyres hard, it is a fact that tyres so pumped, require less effort to propel the machine on good or fair roads, and are less liable to skidding and side slip on greasy roads. If it be required to take out the valve plug and rubber, and it be found to have stuck in the valve body, the wheel should be turned until the valve is parallel with the ground, and a lighted match held under it, The slight heating will release the rubber from the inside of the valve body, and allow it to be withdrawn without damage. The valve plug is hollow with a closed end, but with a small hole made in it leading from the surface into the central hole, this small hole being about 1/4 inch or so from the closed end. The rubber sleeve slides over the hole up to, and over the larger coned end. The rubber over the coned surface prevents the compressed air from passing out of the tyre that way, and the sleeve permits the air from the pump being forced down the valve centre passing out through the small hole, lifting the rubber away and passing into the tyre, but when the pumping ceases, the compressed air in the tyre forces down the rubber sleeve over the small hole and so seals it up. The outside of the rubber sleeve should be rubbed with French chalk to prevent it sticking in the valve body. The nut holding the valve in position in the rim should always be screwed up very tightly to prevent movement in the rim hole, and damage to the valve body.

The freewheel being a mechanism added for the purpose of allowing the rider to cease pedalling when desired, it is necessary that no snatch takes place when pedalling stops, also that it shall never slip or give under the rider's thrust, and also that it be as nearly as possible weather proof. There are many different types of freewheels on the market, and the description of one type will illustrate the general trend of design. Fig. 55 shows the internal arrangement of a good form of freewheel. The chair or toothed wheel runs on ball-bearings, as shown, and these require oiling from time to time. An annular shoulder in this wheel is cut in such a manner that a series of rachets or pawls can engage therein, and the rider's thrust on the pedals is, by means of these pawls, transmitted to the back wheel hub. When the rider free-wheels, the driving chain is stopped and the pawls are carried round over the annular teeth, so making a slight clicking noise. Small springs cause the pawls to drop into the recesses when opportunity offers. A freewheel in good order will engage in practically any position, and will not jam or slip ; if such does occur, first try washing out well with paraffin, allow to drain well and fill up with good and thin oil. If the trouble still exists, the freewheel must be taken to pieces. All the better class make of freewheels can be taken apart though special tools may be required in the operation. If the freewheel was free both ways or slipped sometimes, then look for a defective or worn pawl or defective pawl spring. If such defects are found they must be exchanged for new pawls or springs or a substitute made. Make sure that the interior is free of all foreign matter such as grit, dust, or broken parts, before reassembling, oil thoroughly, and before closing up see that all the balls are present and in good order, change any defective balls. If any difficulty is found in getting the balls to stay in place while all are being assembled, then apply a grease such as vaseline to hold them in position. Tighten up all thoroughly before using on the machine. Should it be found that the pawls and springs are in good order, then suspect defective balls and inspect accordingly.

Fig. 55.