Any single lead-acid cell will read 2.1 volts, so a fully-charged 6 volt should read 6.3 volts. It's also a good idea to check the acid strength with a hydrometer (the glass tube with a rubber squeeze bulb and a weighted float inside). Full-charge specific gravity should be somewhere between 1.2675 and 1.300. A battery with specific gravity below 1.250 is too discharged to load test. A totally discharged battery will have a gravity reading below 1.100.

With the load of a normal starter cranking the engine, not a draggy or shoirted one, a 6 volt battery's terminal voltage should not drop below 4.5 volts. If it does, you've probably got internal problems in the starter. A starter running with no engine cranking load should not drop battery voltage below 5 volts.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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