Electrical/charging system

My bike is an '82 XJ650J (Maxim). Pretty much stock.
Changed out the fuseblock to the wirewerks 6-circuit unit
that uses the ATC fuses. Crimped, soldered, taped, and
di-electric greased the heck out of the connectors.

Took apart every connector on the bike (except inside the headlight,
since bike has a pain-to-remove fairing on it) and cleaned the
terminals with a small file, then filled the backs with silicone
and di-elec greased the connectors inside.

Checked the generator brushes, lots of material left, cut them
a bit with some fine emery cloth and cleaned the commutator
disc with some 400 grit.

When I check the resistance on the green/brown wire, it reads
7.2 ohms...way too high. Checking between three white wire
leads, it reads 0.7 ohms on each pair....again, way too high.

The battery reads 13.3V fully charged, engine off.

Measuring the voltage on the green wire with the engine running,
it reads about 0.9 at 2000 rpms (way low) and goes to a max of
8.4 volts at 5000+.

Measuring AT THE BATTERY TERMINALS, with the engine
running 2000+ rpms it reads 14.9V....which means the charging
system is working properly, correct?? And if so, why are all
my other measurements so far out of spec? Or am I missing
something?

Bike only has 11K miles on it. No other electrical issues, everything
is bright and works and it always cranks and the battery (1 year old)
reads just over 9V while cranking. Headlight (low beam) barely dims
when flasher or brake lights are applied.

On the XJ Electrical Page, it mentions that the regulator box is "generally very reliable. You can verify proper operation by measuring the regulated
voltage on the red wire with the battery fully charged and the bike running."

Question: what voltage should I see?

Also, do I measure the voltage input at the TCI while the engine is
running, or off? Last time I measured it, it was at 10.9V at the Big
Red Wire. My coils were bad, so I haven't measured the voltage
at the coils yet, but again, do I do it with engine running or not?
And if running, does it make any difference at what rpms?


Thanks everyone for your help!

 

The fastest way to do a quick test of your charging system is to measure voltage at the battery with the engine running, and low beam on. Battery must also be fully charged (or, known good) and generally the manufacturer will specify at what RPM the voltage should be read (ie, 5000 rpm in neutral)

Any bike that is putting out between 13-14 volts at the battery is healthy. meaning, the stator or generator is putting out vAC and the regulator/rectifier (if equipped) is changing the voltage to DC (or, is it DC to AC? i get mixed up!).


I don't know if Yamaha gives a voltage reading that the TCI should "see", nor am i sure why your resistance readings vary from what you think you should see... but remember that measuring equipment (type, name brand, and battery condition) can effect the numbers that you are seeing vs what the service manual states.

Worry no more, sounds like your charging system is fine.

-Matt
83 xj900

 

As above too , also i would investigate the 10 and a bit volts at the tci , try to trace where the drop from 12v is occuring [i guess the ignition switch or connector plug] , and if so a clean of contacts/plug might help.

i went throgh mine a few weeks back and noticed a drop from there , so i pulled the switch and dissasembled it , cleaned the contacts , and in removing the switch one also has to unplug the connectors to it so when reassembling the wire loom plugs spray with a good lube [not wd40] and doin all that got the 2 volt drop removed for my heep.

motor running will see a slightly higher voltage 13-14v , motor off but ignition on will see 12v or so , but leave ignition on and engine not started i think the tci shuts down untill it senses the motor is turning then switches itself on , thats all you'll have to remember...good investigating.