Honda HRX217K6HYAA knocking noise, and carbon build up on first season of use.

I bought a used hrx 217yha from a professional yard man last year. He said he only used it 3 times. I checked it really good. It had no scratches anywhere, the blades still had most of the paint on the cutting edge, still had all the stickers on outside. Even the oil looked fresh so I'm sure it only had a couple hrs on it. I ran it last summer and towards the end of the summer I noticed an internal knocking like a lifter which got worse after warming up. It may have been there already but since I had earphones and ear muffs on I may have not hears it. But this last winter I did some maintenance, when adjusting the valve lash to .08 on both valves as is recommended in the manual for this gcv200 engine they where off quite a bit. Also there was excessive carbon build up on plug and inside engine, and oil was pretty dirty. I forgot to mention that I changed the oil after the second time I used it estimating that it had 5 hrs. Also checking rpm's there at 3250, when the manual says 2950-3100 ÷/-100 so its really only 50 over the plus 100. Does anyone know what could be causing this on such a new engine, maybe timing off or something. Ps I will try to send a short clip of the sound.

I will try to post it to YouTube, but I have never used it before. I have a 10 second clip from my phone but I can't attatch it to this post. 
 

I don't really hear anything unusual...
 
Can you manually (or with throttle control) record the engine at a slower RPM?

https://youtu.be/SUYW9xoammk
https://youtu.be/F4xiBSYlBsM
Here's 2 recent videos from today I have the cover off because I'm still working on it. I have mowed once with it this year, and I blocked the crankcase hose and outlet from block with filter media. I don't know if it needs the crank case venting into the intake to run properly. But the knocking is the same either way.

Ok thanks. I remember last year lightly hitting a small stump that I cut low, but I can't remember if it was with the battery powered mower I had before I got this. But I did go over a pile of twigs but I don't believe that is enough to bend a shaft. I haven't really checked the mower deck or clutch area. I checked the oil after using g it this one time and it is clean. Maybe I knocked the timing off. Do you know how to check that. Also when I check the rpm with a plug coiling rpm gauge its 3250
So maybe I need to adjust the governor. Thanks for your help!

The engine can run up to 3,600 RPMs but some federal laws lowered the RPMs (I think for blade tip speed), to lower the RPMs.    Sooo, your RPMS are fine...
 
Again, check the enigne bolts for tightness.  I would pull the entire clutch assembly underneath and then run the engine checking for knocking..  Just to rule that in or out.   Pay attention to how the pressure plate is installed.  
 
With the clutch off, spark plug wire off, machine on it's side (air filter up), slowly spin the engine over checking the end of the crankshaft to see if it's damaged..

<p>Thanks I had this forum open in my tablet and the page wasn't updating, so I just saw your response. I will check everything. I did see that manual from Hondas website.</p>

What's BBC an abbreviation for?

Yep, I replaced one (pressure plate too) awhile ago...

Might want to drain the oil and inspect closely for any "shiny stuff".