Motorcycle Repair: 1982 XJ550 starting issues, regulator rectifier, brown wires

Question
When I last ran my bike in Nov. it seemed that all was good. Trying to get it going for the spring and I'm having starting issues. It is very cold blooded and it usually takes a bit to get it going. But this time with the battery fully charged (new battery in Oct.), I only get a cranks and things stop. Battery is reading full charge.

Checking the ohm reading (three white wires) on the stator, the manual says 0.5 +/- 10%. I'm getting a reading of 1.1 at all three connections. When I check the ohm reading on the alternator (green & brown wires) the manual says it should be 4.8 +/- 10%. I'm getting 5.5 on both.

Manual doesn't say what to do if the readings are out of range.

Do I need to change my stator? alternator? both?

Thanks in advance for any help you can provide.

Answer
Hi Kevin,

It could be a few different things happening here.

First thing to confirm is if your battery has load stamina.
The way this is done is to charge the battery up
and then connect a multimeter or voltmeter
to the battery. Watch how many volts the battery
is reading as you try starting the bike.

The battery should not go below about 10 volts when
starting. If it goes below that it means the battery
is not able to provide enough power under high current
load draw like when starting.

Many batteries go bad even new ones occasionally.

If it passes that test then make sure all your connections
are good and tight and clean in the starting system.

Get the bike running if possible and see what the battery
voltage reading is at idle and at 2000 RPM.

At 2000 RPM your charging system should be giving
you a battery voltage above 13 and up to 14.5 volts DC
You may only get a battery voltage reading at idle as
they don't charge much until above idle.

If it is not reading higher than the battery voltage then
you may have a bad regulator/rectifier or low
stator output.

The stators/alternators on some of these Yamahas used brushes
that could wear out so that might be worth
checking if it doesn't seem to be charging the battery.

I would not worry about some small variations on the ohms
readings as often you will not get any reading at all on a faulty
stator etc.

If the battery and charging system proves out then you
might need to clean up the starter itself and check
the brushes in that as well.

WS
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