Popular ScicJice Mnnt/ih/ 



125 



that of ^hc ryliiider before it is expaiKicd 

 by the rlanipiiisi-mit. It is tiinicd to 

 lia\e .1 Ner\- sniootii siirfaec. In use, 

 tlie drill-press is set in the back gears so 

 the spinclle will rotate slowly, while the 

 lap is revolving. It is also raised up and 

 down by the hand-feed lever. The lap 

 may be expanded slightly after it has 

 been turned and reciprocated for a time 

 and fresh abrasive added. Care should 

 be taken to clean all emery and oil out 

 of the cylinder when the lapping process 

 is completed. If the work is properly 

 done, all the scratches will be eliminated 

 and a smooth bore secured. Deep 

 scratches, such as caused by a loose 

 wristpin, can only be eliminated by 

 re-boring the cylinder.-ViCTOR VV. P-age. 



A Handy Hook for the Automobilist 



AH.-WDY and cheap attachment for 

 an automobile-jack is an iron hook 

 that can be made by an>' blacksmith. 

 It should be just a little shorter than the 

 jack, with one end bent to fit over the 

 top of the lifting head and the other end 

 formed into a hook large enough to hold 

 an axle, and strong enough to lift the car. 

 In this way, the machine can be easily 

 raised in places where it is impossible 

 to set up the jack in the usual manner, 

 for lack of clearance. The hook will be 

 founfl particularly \aluable when the 

 automobile gets stuck in the mud and 

 there is no pry 

 available. In this 

 situation there is 

 never sufficient 

 clearance to use the 

 jack, but with the 

 hook, the car can 

 be raised far 

 enough to get a 

 board, a box or 

 some dry dirt under 

 it. — E. F. Ayers. 



A useful hook 



Simple Cure for Misfiring at Low 

 Engine Speeds 



THE writer recenth- cured a case of 

 misfiring at low engine speeds by 

 a very simple expedient. The engine 

 was a comparatively new one, and had 

 not been run long enough to ascribe the 

 trouble to wear in the inlet valve stem- 

 guides. All manifold joints were tight, 



and there was no air leak around 

 valve-caps or petcocks. The carburetor 

 adjustment was altered without receiv- 

 ing any benefit. A good spark was 

 obtained from both battery and magneto 

 systems, anil as the misfiring was as 

 pronounced with one ignition system as 



/?eaaf Gas Poc/<ef aroi/nd SparA Points in 

 JparA P/uq f/ectrodes Comtastion Chamlxr 

 Misfiring can be eliminated by tapping out 

 the valve-chamber caps 



the other, it plainly was not the fault of 

 the ignition group. The misfiring was 

 not serious but annoying, especially 

 when running the engine slowly on the 

 direct-drive in traffic. 



In remo\ing the spark-plugs to ex- 

 periment with \arious gaps between the 

 electrodes, it was noticed that the plugs 

 did not screw into the cap very deep and 

 that there was a pocket in the valve-cap 

 beneath the spark-plug, as shown at A in 

 the accompanying illustration. As every- 

 thing else had been tried without curing 

 the trouble, the valve -chamber caps 

 were tapped out w-ith a J-2-in. pipe tap 

 so the plugs could be screwed in enough 

 to eliminate the pocket entirely as 

 shown at B, and the edges of the tapped 

 holes were chamfered to make sure the 

 plug would project into the large 

 chamber in the valv^e-cap. After the 

 parts had been replaced, and the car- 

 buretor restoried to its original condition, 

 all misfiring ceased. 



The explanation is that at low speeds, 

 owing to imperfect scavenging and low 

 rate of inlet gas flow, some dead gas 

 left from a previous explosion collected 

 in the small pocket around the plug- 

 points; when the spark took place, the 

 ignition function was erratic because of 

 the poor gaseous mixture surrounding 

 the plug-electrodes. Bringing the points 

 further into the combustion chamber 

 eliminated this condition, because the 

 electrodes were swept by the fresh gas 

 at every intake-stroke. -Victor \V. PAofi. 



