Clutch slippage at heavy throttle [Solved]

[Iarn]

First of all, hello!

Apologies in advance for a likely lengthy post.

I'm new to forums and the world of motorcycle ownership. I've recently purchased my first motorcycle; a 2004 GS500F with roughly 5,000 miles on it from its second owner. I bought the bike with the intention of a dual hobby. Learning how to ride and also being able to perform mods to the bike and get my hands dirty on it, as I love machines and mechanics. Sadly (or not, as working on it has been sort of fun) there have been a laundry list of issues with it that I feel should not be happening with such low miles, and while I love the bike, it's been quite a task getting this it to nominal.

I'm going to give a bit of back-story to the bike, if that might help give possible insights towards a diagnosis of the particular issue I'm having.

I know little about the first owner. It was told to me that it was a young-ish male who rode it for approximately 2,500 miles, got bored of it, then sat it up in a garage for some years. Second owner was a mid 20-something who kept the bike outside his apartment, no covering. He also put 2,500 miles on it. Then sold it to me. I have put about 400 miles on it since owning it and I have a sneaking suspicion this bike has not been well maintained and also ridden very hard/abused, as the mechanical state of the bike is poor.

So far problems include, but are not limited to, in order of appearance.

• Knocking/ticking sound while running below 3k rpm(loose rear valves and bad adjuster assembly) Re-shimmed valves and replaced assembly.
• Bolts in starter clutch completely stripped and shredded by god-knows-what. Metal shavings all inside the engine, luckily the oil filter caught all of them and they caused no serious damage.
• From the interiors of the engine, looks like the oil was scarcely if ever changed. Baked brown in there, now.

And many other, much more minor issues.

I was able to repair all of these myself mostly, but now I'm having issues with the clutch slipping under heavy throttle and I lack much experience with motorcycles to pinpoint a proper diagnosis. Here is what I'm experiencing:

• Under a normal amount of load, the clutch seems to work reasonably well. Shifting in traffic isn't terrible, though you can tell there is a very small uptick in RPM before it catches, versus the expected,immediate, downtick.
• Under heavy acceleration and/or throttle, the tach needle sits on nine yet you feel like you're going no where. If I shift from any gear at 9k RPM, I expect it would downtick to 6.5-7k, yet it hops to 9k and stays there for quite some time until it finally catches and falls back to 5-6k RPM.
• When I'm in top gear, at about 60mph-5k RPM, if I open up the throttle to 100% the tach jumps to 9k and again... i feel like im going no where. It will some time later catch at a reasonable RPM and gain some traction. This, to me, seems to be the easiest to reproduce and most apparent red flag.

Thoughts? I talked to a mechanic friend of mine about this for ideas. I replaced the bad oil that was in it with 4-stroke synthetic for wet clutch. Non-energy conserving. He seems to think that's the cause... I personally feel like that's a superstition of his that I lack.
Short of replacing the oil to dino, what am I needing to replace? Do I need to replace anything? Could the clutch possibly be bad at such a low mileage? I have no idea where to begin with this particular problem.

TL;DR Clutch is slipping at heavy throttle on low mileage bike. Possible causes; fixes?

[Suzuki Stevo]

Sounds like you need to adjust the rough clutch adjustment, #6 could be too tight (no free play)

[Iarn]

If that simple adjustment is all it is, I'll be blown away. I'll fiddle with it tomorrow. Thanks 

[bmf]

I'd be amazed if the clutch is bad , they last for over 100k  if not abused.

[Iarn]

Okay, just finished the adjustment, unfortunately it's raining.  As giddy as I am to take it for a spin and see if that's done anything I'll be waiting until it's dried up a bit I'll report back with the results.

[Iarn]

Stevo, you were absolutely right. That screw was way too tight. I adjusted it to the proper settings and rode it for 10 miles. She runs like a beaut now! I really am amazed at it being a little screw...  Thanks a ton and good call.