No-Start issue stumping me!

[Bmel]

Hi all, new here, with a question. Apologize if it's been answered numerous times.
I've got a 1979 CB750F, have had it for 25 years.
My problem is, when the bike gets hot, it won't start, it just clicks and won't turn the starter over.
Like, after a ride, or, stopping at the gas station, if I try to start it after 5 minutes or so, nothing.
But, if I wait 15 minutes or so, it fires right up.
It really plays hell with stopping at the store or somewhere real quick, cause then I have to wait until it wants to start.
When I get home after a ride, I hook it up to my battery tender, and, after 15 minutes or so,
the indicator lights on the tender show that the battery is more than 80% charged.
It then takes 3 or 4 hours to reach 100% charged.
I put a Rick's starter in it last year, hoping that that would solve the prob, nope.
I then replaced the battery, the starter solenoid, the negative cable and both positive cables, and made sure the connections were nice and clean.
It seems like something is getting too hot, and not wanting to work until it cools off for 15 minutes or so.
I was thinking the starter might get too hot and "swell" up to the point where it draws too much amperage from the battery.
Then, when it cools down enough, everything works fine, and it starts right up.
I don't think it's the starter, battery, solenoid, cables or connections, and if the charging system wasn't working,
it wouldn't fire up after 15 minutes of just sitting there cooling off.
Sorry so long-winded, just wanted to provide as much detail as possible.
Ideas, anyone?

 

[brettp]

It does sound like a starter problem. When you hear the click, that tells you the relay is working. But if you want to test the connection between the relay and starter, put a screwdriver across the relay terminals. The battery is then sending juice straight to the starter. If the starter doesn't turn, your starter needs to be cleaned or replaced.

 

[NormK]

Nice filter setup you have there, getting rid of that clumsy big airbox will make it much easier to work on. Did you have to play with the jetting?

 

[Bmel]

It does sound like a starter problem. When you hear the click, that tells you the relay is working. But if you want to test the connection between the relay and starter, put a screwdriver across the relay terminals. The battery is then sending juice straight to the starter. If the starter doesn't turn, your starter needs to be cleaned or replaced.

The starter is a Rick's Motorsports with the 4 permanent magnets upgrade that I installed in March 2023.
It doesn't turn that freely when I turn it by hand.
I'll try jumping the relay next, thanks.
Something's telling me it's the rotor/stator, when I ride it for 30 minutes or so, and throw it back on the battery tender, it takes 2-3 hours to show a full charge green light.
And, I think when it fires back up after sitting for 15 mins or so, the battery's had time to build back up a bit more amperage.
At this point, the rotor/stator/brushes are the only things that I haven't replaced! lol

 

[Bmel]

Nice filter setup you have there, getting rid of that clumsy big airbox will make it much easier to work on. Did you have to play with the jetting?

Thanks, I went to high school with a guy who raced for Honda back in the day (1979).
He was a Senior and Me and my boys were Sophomores.
In 1979, we were riding 400 Super Sports, and he got the first CB750F in town, we were blown away... lol
He and a buddy opened a motorcycle performance shop in the early 80's, and Honda bought it out a few years later.
He's been working on the DOHC's forever, and he does my tuning.
I was having the typical issues with the carbs getting out of synch and creating that slight lag before the engine responded,
so, he suggested we go with a set of aftermarket Keihin CR Smoothbores.
So, we went with the K&N Air Filters, the Keihans with bigger jets, exhausting through a Vance & Hines 4 into 1 header.
It really flows well throughout the entire RPM range.
He also dropped a set of 900F Cams in it, all he needed to do was a bit of Dremel work to get enough clearance...

 

[brettp]

If the starter doesn't turn over when the bike is warm, then you have a starter or starter circuit issue for sure. If you jump the solenoid/relay and it doesn't turn over, and you're convinced the starter is good, then one of your connections somewhere in that circuit is an issue.

 

[NormK]

Nice bike you have there, lots of polishing gone on there

 

[Bmel]

Nice bike you have there, lots of polishing gone on there

Thanks, mate, it's a labor of love!
cheers