nighthawk 550 electrical problem

Krusty,

Your caution is why I asked before making the decision on thi
one. Yes my alternator has a fan and yes the bike does have a cdi bo
under the seat. The clymer manual says there is not test for that box
It is either good or bad. Mine is good because the bike fires properl
when the pickup is working correctly. The rotor does turn as
suspected. The test of that black wire and white wire is straight ou
of the clymer manual and it fails the resistance test clearly on
cheap multimeter and an expensive one. What I am not sure of is wha
the significance of the resistance between these two leads that make
the stator bad.

Jef

 

My concern is to help you avoid spending money needlessly on parts that
may
not need replacement. The charging system, consisting of alternator,
rectifier regulator, and battery is the system most often misunderstood
and all the parts very often get replaced one at a time until the
problem is found and the owner gets stuck with perfectly good extra
parts.

Good. Now that we are clear on those points, the only other possible
reasons why the stator wouldn't put out the required open circuit
voltage are that the magnets on the rotor have lost their permanent
magnetism and the distinctly odd ball possibility that the stator or
rotor is the wrong one for the motorcycle. (1)

It's certain easy enough to find out if the permanent magnet rotor is
still magnetized, just hold a piece of iron next to it and it will grab
the iron and hold it.

Permanent magnets can lose their magnetism from being heated, being
struck hard blows with a hammer, or from being exposed to an
electromagnetic field.

The indication of low resistance is that some of the windings of the
stator's CDI charging coils are shorted out.

When you run the open circuit voltage test on the yellow wires, are the
black and white wires also disconnected? If the black and white wires
are disconnected and the engine runs, that indicates to me that the CDI
system will start the engine on battery voltage too.

The indication from the 1 volt you got from the open circuit test (if
you checked from yellow to yellow to yellow with the engine running at
around 5000 RPM) is that the stator battery charging coils are also
shorted out.

The decision to spend $100 on having your stator rewound, is, of course
entirely up to you, and I hope that my explanations have helped you
make the correct decision.

(1)We read about the strange case a few years ago where the owner of a
Suzuki GS750 had mismatched the rotor from one motorbike to the stator
from another motorbike and the number of magnetic poles was incorrect
so the required north and south magnetic poles were not aligned with
the stator poles at the correct time and there was no voltage output.
As I recall, that fellow had one 12-pole part and one 18-pole part, and
that's why the north poles and south poles were never aligned to
produce voltage in the stator. That one was a real headscratcher.