motore usato: cosa controllare?

[Scarabocchio]

fate bene a prendermi in giro ma vorrei dire qualcosa a mia discolpa.
avvicinando l'orecchio al coperchio valvole, oltre ad ustionarselo, si sentono i tic tic dei bilanceri e anche un po' di fuf-fuf di aspirazione (o di scarico). il mio problema, non avendo auscultato molti motori, è capire il livello entro cui questi rumori sono normali e quando invece sono eccessivi. se leggo la tabella qui sotto li sento quasi tutti, però il motore non da (risgrat) per il momento problemi. quindi?


Knocking

Sounds Like: Hammer hitting engine block. Hard mechanical sound with frequency proportional to engine RPM.
Mechanical Causes: Connecting rod bolt loose [4] - Piston hitting valve [4] - Worn connecting rod bearing [4] - Flywheel loose [5]
Fuel Causes: Defective injector [2] - Excessive fuel [3] - Injection timing too far advanced [4]

Rumbling

Sounds Like: Slow speed dull sound like assorted rocks being turned in a large drum.
Causes: Propeller shaft out of balance [2] - Propeller out of balance [2] - Cutless bearing worn [2] - Gearbox bearings worn [4] - Drive plate worn or loose [4]

Rattling

Sounds Like: One or a handful of nuts being shaken in an empty metal can.
Causes: Excessive valve clearances [2] - Loose accessories [2]

Squealing

Sounds Like: Sound of car tires during a racing start.
Causes: Fan belt slipping [1] - Lack of lubrication on piston [3] - Gasoline in fuel tank [5]

Hissing Air

Sounds Like: Escaping gas. Occurs intermittently as a piston approaches the top of its compression stroke.
Causes: Leaking injector seating washer [2] - Leaking cylinder head gasket [3] - Leaking inlet valve seat [4]

Clicking

Sounds Like: Light metallic sound that can occur once or continuously.
Causes: Starter solenoid engaging - once is normal [2] - Excessive valve clearances [3]

High Pitched Whir

Sounds Like:Very high speed zing that rapidly increases in frequency.
Causes: Starter still energized or engaged [3]
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How Likely: [1] - Very Common. [2] - Common. [3] - Possible. [4] - Rare. [5] - Very Rare