4 stroke block

the block houses the pistons con rods and crank. the block is wear the combustion happens there for the block is  very strong and usauly made of cast steel. inside the block are boars wich house the piston

PISTONS
 the piston slides up and down the boar buy the rotation of the crank. the rotation of the crank starts of either by a starter moter or a bump start. the piston draws air and fuel into the boar, compresses it, the park plug ignites the air and fuel pushing the piston down creating a rotating motion in the crank to help pump the other pistons up and down. with out the piston it would be impossable to create compression or power. on a 2 stroke some pistons are curved to circulate the air and fuel around the boar instaed of straight out the exhaust. on a 4 stroke standerd pistons have flat tops or small indents so the piston dosnt hit the valve. on performance engins when high revs or a higher octane fuel is used a forged piston can be uesd for exxtra strength so no holes or damge can be don to the piston head. the piston has sevral groves on the side for oil rings. these oil rings help lubricate the boar and piston as it pumps up and down and also stops oil from getting on top of the piston to wear combustion takes place. worn or broken rings creat alot of smoke as oil is being burned with the air and fuel.


GUGEN PIN
the gugen pin holds the piston to the con rod.  it act like a bearing with help of the oil for lubrication so that the piston can stay straight in the boar and the con rod can rotate with the crank. it is important that the gugen pin is strong as a weak gugen pin can cause alot of damage if it brakes.on a 2 stroke the gugen pin runs on roller bearings as the lubrication is air, fuel and oil. on a 4 stroke it ues oil to lubricate and rotate. with out oil the parts can heat up and melt togeather or sease reacking the engin.


CON ROD
the con rod or connecting rod coneect the gudgen pin and piston to the crank.  the con road connects to the crank by main journals. instead or caged roller bearings in these journals like on a 2 stroke there are oil groves and sleeves wich relei on the oil to lubricate these moving parts. when inspecing the con rods its best to check that they are straight non damged like buring or chipping and havnt been case hardend as this can effect the overall strength.



CRANK
the crank is a vital part of the engin as it truns  up and down movement into rotaing movement wich is transferd onto the fly wheel. the crank is held to the bottme of the block by main journals. these main journals have the same lubricating  system as the journals that hold the con rod to the crank.  the crank holds the kenitic energy  of the piston and  helps pump the other pistons around.  when inspecting the crank i checked the size of journals. if it was bent with a dti gaguge.  the crank was fine with the manifaciures spces.