Expanded charging system guide (In progress)

yep brushes are easy cheap and sometimes that's all it is. Check all your wire connections especially the ground strap from the battery to the frame, wiggle,, tug remove the bolts, clean connections with sand paper grease reassemble. On the 80 up bikes fuse boxes tend to fall apart. The little clips that hold the fuses get weak and break off or just don't make good contact. After those basics then start testing deeper.
 
hey guys, i did the slap test and it seemed to work great, so i removed the brushes and they look worn down to me. I know it should be replaced if 7mm or less but how do you measure that? there is a line on the brushes , do i meausre from there to the end?? thanks alot!!
 
Overall length from the end that contacts the rotor to the end where the spring sets. If you can see the line then they are Yamaha brushes, probably from the factory.
The factory put the line on there as a wear limit.
If not much past the line get new ones. Get new ones anyway, don't cost much.
Leo
 
ok guys i need a bit of help. i put the new brushes in and then tightened everything down and when i tried to start it , it was acting like the batterie was dead. well after putting my harley batterie on it i soon realized i had to loosen the stator so that the bike would turn over like sapose to. ok so i got it started and while checking if it was charging i tried to tighten the stator screws but it killed the bike. i loosened them and tried to restart it.. now it wont start. i checked to see if i was getting a spark in the spark plugs and i dont see one..... is my voltage regulator bad???? thanks guys.. getting frustrated :(
 
ok guys i need a bit of help. i put the new brushes in and then tightened everything down and when i tried to start it , it was acting like the batterie was dead. well after putting my harley batterie on it i soon realized i had to loosen the stator so that the bike would turn over like sapose to. ok so i got it started and while checking if it was charging i tried to tighten the stator screws but it killed the bike. i loosened them and tried to restart it.. now it wont start. i checked to see if i was getting a spark in the spark plugs and i dont see one..... is my voltage regulator bad???? thanks guys.. getting frustrated .. im getting full power to the stator also.
 
There are short screws and long screws that hold the brush holder and the wire brackets to the face of the stator. If you mix them up a long screw will hit the rotor, it sounds like that's what happened.
 
i didnt get the screws mixed up. is there a chance that the stator can be shorted out causing it to magnetize to the rotor? also while showing my wife what it was doing i seen the stator throwing sparks , is this normal?
 
Is the rotor on all the way? I might pull the stator off and look inside. Look to see if the rotor and stator show places where they touched.
Leo
 
after ohming out the voltage regulator and stator i found that the start had a dead short on all three white wires. i installed a new stator and now the bike is running and charging.... :) thanks gary and all!!!
 
Does the "slap test" work with the older systems...specifically a 1977 XS650D...I have bike that runs beautifully, but does not seem to charge the battery.....I replaced the battery...have done the test for the regulator and rectifier, looked at the brushes (should one be shorter than the other by the way-one seems to be wearing and the other looks brand new) fixed a bunch of connection and still can not get the battery to charge...HELP!!!!!!!!:banghead:
 
Yes all XS650 use the same electro-magnetic rotor system. The slap test works for your 77.
 
Also the brushes do wear at different rates, the inner travels a shorter distance per revolution than the outer.
They start out the same length but end up different.
Is the short one less than 3/8 inch? If so you need a new set.
Leo
 
Hi I'd just like to clarify: when doing the “slap test” are you supposed to have the bike running or just the ignition switch on?
 
second question: I put a voltage meter on the two bolts/wires holding the brushes; when the bike is running I should see a current right? If so what should I be looking for?
BTW: I pulled the brushes and they looked like new.

Thanks!
 
second question: I put a voltage meter on the two bolts/wires holding the brushes; when the bike is running I should see a current right? If so what should I be looking for?
BTW: I pulled the brushes and they looked like new.

Thanks!

You should see a voltage of 10 to 13 volts with engine idling. When you rev the engine to 2500 to 3000 rpm you should see the voltage on the brushes reduce to 5.5 to 7 volts. The regulator reduces the voltage to the brushes/rotor as the alternator output increases due to higher rpm.
 
You should see a voltage of 10 to 13 volts with engine idling. When you rev the engine to 2500 to 3000 rpm you should see the voltage on the brushes reduce to 5.5 to 7 volts. The regulator reduces the voltage to the brushes/rotor as the alternator output increases due to higher rpm.


Just to clarify; this is measuring the voltage directly from the bolts/wire holding the brushes right? The reason I'm asking is you mentioned the regulator reducing the voltage - wouldn't that happen after the 10-13 goes through the regulator?

BTW: I tried the slap test again (only ignition switch on) and nothing. now onto step 3?

Even though I bought a 79 bike it seems like it came with an 80 or later motor because it has a TCI pickup. Also, I think I have a solid sate regulator??? Can you confirm?
see images...
 

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