Would you say its the alternator?

[Guest]

Ok, the battery was sitting at 12 volts, the bike started, then after about 5 min, the voltage started to drop, I reved the engine to about 5000, and there was no voltage increase at the battery.
I think its the alternator, what do you think?
Are they expensive?

[md86]

AT 12 volts , or slightly above 12 volts ? SHOULD be like 12.5 or better fully charged . And if the voltage doesn't go up any while it's running , then yeah , it's PROBABLY an alt. issue . But your battery very well could be done , too . Dunno about cost , but you should be able to pick up a working used one for a fraction of the price of a new one . You could try our resident parts guy Special K (PM him) , or hit e-bay .

[Black_peter]

Alternator, voltage regulator (built in)
For sure.. Even if the battery was toast the voltage should go up..

Unless the battery is fooling the regulator into
not charging the battery... Did you chec the voltage at the alternator?

[duff daddy]

yea its prob like the other 2 said but id check to make sure your not drawing any extra current off that battery to give it a big strain

[zleviticus]

check your wires as well... an old car i had it was a short in a wire... i argued and argued with a mechanic that is was NOT the alternator and then he foudn the short where i told him it was.. (since i had changed the alternator in a parking lot the night before i knew it was not that) On crimp and $20 later i was set and pissed at the same time.

[Guest]

I checked all the wires and everything looks good, I think the batt is ok, because it held its charge of 12 volts all night, like I said I reved the engine to 5000 rpm, and there was no voltage increase, they only other possibility is like someone said, the battery could be telling the regulator that it does not need anymore charge.

But I think thats very unlikely.

[md86]

But your battery should be at MORE than 12 volts fully charged , and even a crappy battery will hold a charge of 12v overnight , trust me I've seen it . But yeah , you probably need to contact Special K for another alt assembly (the regulator/rectifier is built into the alt. ) .

[Guest]

Thanks, It must be the alternator, I just had my battery checked at walmart and crappy tire, they say its good.

Now if it needs a new alternator, or regulator, should I just get the alternator, or regulator whatever one is no good. Or should I not waste my time and just get the whole assembly, because they are separet parts within the alternator?

[Süsser Tod]

Definitely alternator/regulator issue. Even if the battery is fully charged, you should get a reading of ~13V on the battery terminals.

The voltage won't change if the battery is charged, just the current going into the battery.

In this case, the alternator or the regulator aren't sending any juice to the battery, and that is because they aren't generating it or letting it go through.

[DreKat]

with the bike off the battery would be around 12V and with the bike oo the battery should rise to 14V or 15V.