TOPIC:

Turns over pretty well when cold but not when it's hot. voltage goes up with throttle on a voltmeter, so I assumed it was the battery.
Just spent $160 on a new glass mat batter, charged it up for 1/2 a day and went for a long ride.
Got home and tried to start it....NO GO. have to sit for 20 mins till it barely has the poop to start.

Could it be too far advanced? Or how do I check that it's really charging?

It's an 81 GPZ1100 motor with a 1136 kit.

I really should get a service manual if I can find one. Frustrating.

Hi Steve
A manual is a MUST !!!
Meanwhile , other things that could be the problem is a starter that is going. Or as likely your battery cables can go bad too. Heat makes all the electrical components act up. ( More internal resistance ) You may have read other electrical post where a hot ignition coil fails to work m even though once cool it works again. So get that manual and start checking .. Remembering how old the wiring system is
Good Hunting
Dave

Coast Steve wrote: . . . how do I check that it's really charging? . . . .

With voltage meter connected to the battery posts, would look for 14+ voltage D.C. at 4000 rpm.

Would also assure integrity of the ground connection where the cable from the negative battery post attaches to the engine.

Good Fortune!

Patton wrote: Would also assure integrity of the ground connection where the cable from the negative battery post attaches to the engine.

Yep. Sounds like a ground issue.

Any chance that it's overheating and partially seizing? Does it crank faster when it's stone cold (without charging the battery)?

Much faster when it's cold yes.
Not sure but after a long ride it sounds like it's too far advanced and just can't quite fire up. after a bit of time it's good again.

i'll look into it today I hope. Will check all wires.

The bushings in the motor could be worn out.
Steve

Have you recently stripped the motor, the timing may be out?

300 miles since a rebuild. I got it like that.

I'm really thinking it's the timing too.

Need to wait for a manual to check other stuff but I may be able to Goggle timing on an 81 gpz 1100 to check it.

I'm with SWEST on this one, been there, done that, bought the T shirt.

Is it a bitch to change them?

That's too bad if that's the issue. The shop back in Ontario put in a new starter clutch and bearing for the starter for me before I had the bike shipped. It was making a horrible starter noise before they tell me.
They could have done the brushes too. Damn.

Tell me it's an easy job. I don't need any big expensive jobs right now. The wife still hasn't forgiven me getting the bike to begin with.

What engine is it? On the big fours the starter motor is easy to get out. I had three of them. I took the best parts and made one good one. Just switched the two ends, cleaned up the aperture and put the best brushes in. The bushings are in the two ends. I'll be buying a spare starter to have on hand. Fairly cheap and they fit a wide range of models.
Steve