Troubleshooting Charging System

[coffee_brake]

My first thread seems to have bogged down, so here goes:

My '02 is very hard to start when the engine is hot. Let is sit in the parking lot for 10 minutes or more and it's fine. But try to start it at, say, a long traffic light where you would normally turn the motor off and then the starter motor groans, can barely turn the motor over. Sometimes it just won't start when hot.

The battery is checking out OK and holding a charge. When I hit the start button it drops to 11 volts. Then it takes a full minute at idle for the charge to reach 13.5 volts. It does not go above this, no matter how high I rev the motor.

The manual says it should reach 14 volts at 5k RPMs, but it doesn't. It won't budge from 13.5.
The manual also says the resistance at the wires from the stator should be 3-4.5. Mine are both 6.

I'm trying to understand why the motor doesn't want to start when hot but is just fine when cooled off.

Any ideas?

 

[eatatjoz]

Your battery shouldn't drop to 11 volts.
It could be...
bad ground on the rectifier
bad battery
the splice under the seat. http://vmax.lvlhead.com/tips/splice.htm
or in my case the rectifier itself plus a dirty starter.

 

[coffee_brake]

Dirty starter?

It's got 40k miles, what kind of dirty happens to the starter?


Thanks...

 

[KosRider]

Coffee_Brake, a similar thing was happening with my new 06. What I found the key contributor to be was the ground strap that attaches / bolts to the engine (right next to the oil plug cover where you add oil to the engine) When I remove this grounding strap / wire and cut away the covering where the wire attaches to the connector, I found that the connector was ONLY crimped onto the copper ground wire. When the engine gets hot, this heat transfers to the connector end, and expands the mechanical crimp and thus creates a POOR ground connection which prevents the starter from getting the full voltage needed to properly turn over. Once I soldered this copper ground wire to the connector and retaped the end - never had this hot starting problem occur again !

 

[MaxMidnight]

Also note that the starter brushes earth through the body of the starter.

If all else has failed it might be worthwhile stripping it and have a good ol' Spring Clean?

 

[coffee_brake]

Excellent advice, thank you both. It just doesn't make sense for it be a hard start when hot so I would guess that both the engine ground and a dirty starter are worth looking into.
Thanks!
If anybody has any idea why a cold bike won't charge over 13.5 volts, I'd sure like to hear it....

 

[dannymax]

Wouldn't bad or marginal grounding affect the charging rate too? Try cleaning the grounds and see if there's a difference.

 

[coffee_brake]

I sure hope so. I like cheap and simple fixes very much!