Worn Stator or Charging System?

[sartoriusrock]

Hi all,

I was recently having charging system problems with my 1982 Special. After consulting Curly's charging system guide, I found out that the rotor was shorted (low resistance) and thus replaced it. When I put the new rotor in, I did a bad job putting the stator back on, which was pretty obvious when the starting motor wouldn't turn it over. I inspected the stator, made sure it wasn't damaged, and re-installed it, making sure it was square.

Obviously, I didn't do a good job; after about 15 minutes of running time (with, finally, a good voltage to the battery), I noticed the engine was not running well at all; from idle, I had a hard time getting the engine above 2000rpm, and when it did, it would surge for 10-15 seconds before it would run smoothly. Now, even after a carb clean, the bike won't run well at all.

So began the work. We opened the left engine cover and discovered a worn through stator (it was about 1/3 of the circumference, and each coil had a strip about 1/8" worn through). While this may seem like a smoking gun, we did electrical tests and found that the stator was putting out decent AC voltage and resistance. Also, when we ran the bike, with the throttle wide-open, it would eventually gurgle its way up to 4000rpm, but was killed when we pulled the brake; this seems to indicate a charging system problem.

My question: what is wrong with my bike, and what do I need to do to fix it????

 

[retiredgentleman]

Hi all,

I was recently having charging system problems with my 1982 Special. After consulting Curly's charging system guide, I found out that the rotor was shorted (low resistance) and thus replaced it. When I put the new rotor in, I did a bad job putting the stator back on, which was pretty obvious when the starting motor wouldn't turn it over. I inspected the stator, made sure it wasn't damaged, and re-installed it, making sure it was square.

Obviously, I didn't do a good job; after about 15 minutes of running time (with, finally, a good voltage to the battery), I noticed the engine was not running well at all; from idle, I had a hard time getting the engine above 2000rpm, and when it did, it would surge for 10-15 seconds before it would run smoothly. Now, even after a carb clean, the bike won't run well at all.

So began the work. We opened the left engine cover and discovered a worn through stator (it was about 1/3 of the circumference, and each coil had a strip about 1/8" worn through). While this may seem like a smoking gun, we did electrical tests and found that the stator was putting out decent AC voltage and resistance. Also, when we ran the bike, with the throttle wide-open, it would eventually gurgle its way up to 4000rpm, but was killed when we pulled the brake; this seems to indicate a charging system problem.

My question: what is wrong with my bike, and what do I need to do to fix it????

You replaced the rotor. On the TCI bikes, the rotor has a small magnet that triggers the pick-up coil. I don't know what rotor you bought but, some re-built rotors have come back with very weak magnets. The magnetic field of the alternator rotor may be over whelming the weak pick-up magnet. You could unplug the rec/reg unit and run the engine to see if the engine will run normally when there is no alternator magnetic field present. If that cured the problem, then there are tiny very strong magnets available that riders have glued onto the rotor.

The TCI does not like low voltage. You say your voltage is normal. What battery voltage do you have at idle and at 3000 rpm?

 

[sartoriusrock]

I actually tried unplugging the rec/reg unit and it helped. Upon replacing the rotor, as the replacement had a warranty (and plugging back in the rec/reg), the bike started up and ran well for about 10 miles. However, it soon began the exact same problems it was having before. I will try the magnet trick, but where can I find them?

 

[Dennis]

radio shack
2 for just over a buck I think it cost me

 

[sartoriusrock]

Thank you! I will let you know when I have them installed. Can you give me suggestions on installation techniques? Where on the rotor should the magnets go? Pictures would be appreciated if possible!

 

[weekendrider]

The additional magnet goes directly over the old one.

 

[XSLeo]

Radio Shack item#64-1895 is the magnets you need. they are 3/16, 4.5 mm. A two pack is $2.19.
JB Weld is a good "glue" to use, just get everything very clean.
Leo

 

[Dennis]

Just watch for clearance issues when screwing the pick up back on
There is a thread somewhere with very good pics of the magnet on the rotor

I found the thread
http://www.xs650.com/forum/showthread.php?t=10561

 

[sartoriusrock]

@XSLeo thanks for the item # and the glue! @Dennis, I have seen that feed but couldn't find it, thanks for the link. I will order these magnets and hopefully it'll work. Wish me luck!

 

[sartoriusrock]

well, i put in the magnet, and nothing happened. it ran just like it did before. since it runs better when the reg/rec is unplugged, could that be the problem?

 

[retiredgentleman]

well, i put in the magnet, and nothing happened. it ran just like it did before. since it runs better when the reg/rec is unplugged, could that be the problem?

OK back to basics:
What voltage does your battery measure with the engine off?
What voltage does the battery measure with the engine idling (wait a few minutes after starting) at 1200 rpm?
What voltage does the battery measure with engine at 3000 rpm?

 

[sartoriusrock]

off: 11.9-12.2

idle: 12.2-12.4

3,000rpm: 13.5-13.8 (in case you're wondering, it won't climb higher than 13.9 so it would seem that the regulator is working)

 

[retiredgentleman]

off: 11.9-12.2

idle: 12.2-12.4

3,000rpm: 13.5-13.8 (in case you're wondering, it won't climb higher than 13.9 so it would seem that the regulator is working)

You are only getting partial charging.

A fully charged battery (engine off) should read about 12.4 to 12.5 volts.

At idle battery should read about 13.0 to 13.5 volts.

At 3000 rpm you should read about 14.1 to 14.5 volts.

These bikes run much better if your charging system is putting out the voltages I mentioned. However, if everything else was normal, those voltages might be considered acceptable.

Maybe you can refresh everyone with what exactly the engine is doing badly now.

 

[sartoriusrock]

Well, the engine basically won't run above idle. When I twist the throttle it gurgles and pops, as if there were a carburetor problem, but when I unplug the reg/rec unit, it runs fine (which you said earlier might indicate a weak pickup magnet), but I tried putting in the stronger one from radioshack and there was no improvement.

 

[retiredgentleman]

Well, the engine basically won't run above idle. When I twist the throttle it gurgles and pops, as if there were a carburetor problem, but when I unplug the reg/rec unit, it runs fine (which you said earlier might indicate a weak pickup magnet), but I tried putting in the stronger one from radioshack and there was no improvement.

When an engine will not respond to the throttle (cannot increase rpm) it would point to a blocked pilot circuit/pilot jet.

It appears that the TCI is failing whenever there is normal alternator output/rotor magnetic field is present. Replacing the TCI with a known working TCI is the only way to confirm that.