is it my battery? - or my alternator?

so.... my battery went flat (yep, like everyone elses) and i took it out and charged it up.
i left it on the bench a few days and it kept its charge.
fitted it.... rode with it for 30 miles or so over a few weeks.... then it lost its charge!

so... is the battery duff?

how can i check for a problem with the alternator?
do i hold a multimeter over the outputs of the alternator when its running???


any ideas?

Use your multi meter when the bikes running hold it on the battery terminals to see if your altinator is kicking out 13.5volts. i think!!

[Speedy]

Voltage output should be about 13.5VOLTS,Check across battery terminals. Get a OPTIMATE charger if your gonna leave your bike un-ridden for awhile,you can leave it connected all the time,and it 'maintains' your battery.I've got one.When I started mine after being stood for a while,it fired immediately.

As BILLY said, stick ya multimeter to DC and see what you get across the battery. Measure it with the bike off first, should be about 12.5+ volts. Start the bike and see what the voltage is then. Even with lights on it should be greater than the sitting voltage you just measured. Then rev the bike up, don’t be surprised if the voltage drops slightly as this is the regulation. A nice healthy charging system should give you between ~13 and 14.5v whatever the revs. If it goes to 15v+ something (reg/rec unit or genny itself) is foooked … if it struggles to get over 12 then something is foooooked too

Let us know the results and can advise other tests from there.

[TSM]

I thought that on tickover it would read about 13.5 and when you rev up it should go to around 14. Well thats what mine does and works fine.

i have jus noticed that my battery isnt actually charging..... ie, its full
now- this tells me that the problem may lie with the starter motor

where is the starter motor? and what are the common symptoms of a dodgy starter motor??

im a little puzzled to be honest

If your battery not charging becase it's showing as full the problem could sill be your battery! On a curvey the starter motor is located below the front cylinder behind the exhaust! It's about 5in long by 3in in diamiter with a thick cable coming out of it!!!!

If your battery is ok look at the starter celeniode its located under the riders seat at the right behind the infill pannel!!!!! ps; it's in a green box!

well, i replaced the battery last week
all seemed well, bike started fine
not really used it much.... a couple of rides maybe
out on it todays and it seemed a little unhappy starting.... then stopped for gas and im back to square 1-
it seems like the battery is dead, the starter tries, but not very hard!!!
it makes whining noises and fades out... with the occasional #clunk#

i have checked the battery with (my new) multimeter - it has 11.6V
the battery that i replaced has 12.6V !!!!! (did it need replacing?)

is the issue current? i cant seems to get an amp reading from either battery.

im kinda counting out the alternator.... unless a flat battery gives good voltage but zero Amps.... will a flat battery give 12V???

im thinking starter motor again. ???

my bike starts fine from a bump start and ticks over nicely....

HELP ME!!!!

more than likely your regulator/rectifier is fried, it is the weak point in most motorcycle charging systems, including the SV