gt550 charging quits above 6500 rpm

[r3tro74]

So the gt550 seemed to not run as strong as I remembered last year. It pulls good from 3500 but tapers off about 6500. 6500 to 8000 is OK, but I thought it used to have more.
I’ve been leaving about 4:30 am to go to work and don’t normally spin it up like that in the dark hours. The past few mornings I’ve had raccoons, fox, and deer in my path on the back roads, so I took the expressway. I wound it up pretty good on the on-ramp and starting about 6500 (the same time as the engine power tapers off) the headlight dims quite noticeably and stays dim until the RPMs come back down. I never noticed this before due to generally just putting around when it’s dark out.
I’m going to tear into it tomorrow. I cleaned and greased all the connections a few years ago when I had the whole bike apart. It still has the mechanical regulator.
Any tips or advice are appreciated!
Thanks

[jabcb]

Check the voltage vs. RPM with a multimeter. Check with & without the lights on.

[r3tro74]

OK. Voltage is above 13 @ 2000 rpm with light on or off. Up to 15.8v head light off/ 14.5v head light on. I need to wire a meter where I can see it when riding to actually duplicate the condition. The battery is only 11.2v w/ engine off. Ive been through a couple of batteries now. Ill get another battery, wire up a meter and try again. Recomend a different type of battery? This one is the old style lead acid.
Thanks

[Alan H]

Motobatt are excellent - can't leak and more cranking power for better starting.
Not much more expensive than lead acid.
There's one on the GT550K and one will be on the GT550A in a couple of weeks when it's ready to be started.

[jabcb]

15.8V is too high for modern AGM batteries. You should not be getting a reading that high on one of the triples. The 14.5V reading is OK.

So the voltage regulator is suspect. Its mechanical so you may be able to clean & adjust it.
The rectifier might also have an intermittent problem when its hot.

Since you ride the bike to work, if the cost isn't an issue I would replace both the rectifier & voltage regulator with modern parts from Oregon Motorcycle Parts:
http://www.oregonmotorcycleparts.com

How long are your batteries lasting?

[r3tro74]

Ill order the new rectifier and regulator. Ive been wanting to upgrade the ignition sytem too (this winter) so Ill be set to do that.
The battery is done after a riding season. I top off the acid level once or twice and bring it inside for the winter. It just dosent last. I've been kickstarting it.
Thanks

[r3tro74]

The new regulator and rectifier from Oregon Cycle are installed along with a new battery. I adjusted the regulator to 14.5v at the rectifier output @2000 rpm per the instructions that came with it. All seems OK now. The parts fit in place like the originals. A new harness connector body came with the regulator that your to swap over to the bike harness but the new body dosent fit the bracket on the frame without some modifications. I ended up swapping the regulator side connector body from the original to the new regulator as the termanals fit either body. I did replace all the terminals that were supplied with the regulator, just used the original bodies.
Thanks.