A fouled spark Plug will not start the engine and a dirty plug on the outside will sometimes cause engine to miss, and be hard to start, especially if the weather is damp. The engine is fitted with high grade babbitt, in main crank bearings, and the connecting rod crank end, which, with proper care, should last a long time. These babbitted bearings are poured and not cast separately. The bearing caps are provided with thin paper shims for proper adjustment. A loose bearing soon pounds out, and is the main cause of broken crank shafts.
Loose bearings allow deflection enough to crystallize and break a shaft if neglected too long.
Keep bearings adjusted so that the nuts are down tight on the cap, and shaft is not loose in bearing. Remove some of the paper shims when necessary. To locate looseness in main bearings, lift up under fly-wheel rims, with a bar, and see if shaft lifts in bearings. To locate looseness in crank pin connecting-rod bearing, turn engine backward and forward, placing thumb on connecting rod bearing at crank cheek. Looseness can be detected.