Why am I losing power?

During the summer I was running a Staton-inc Friction drive + Robin Subaru Eh035 and I went up hills just great and went upwards of 28mph.

Recently I moved it off the Raliegh cruiser I had it on, and put it on a new Fito Modena GT and it's just not getting the power it used to have! Won't go up hills, and the speed has lowered significantly also.

I plan on doing an oil change because I've never done that on the engine (the previous owner said he hadn't done one either and he had it for 250 miles).

My thoughts of why:
1) The angle that I've mounted it. Will that reduce my power? Please see pic.
2) The tires aren't smooth enough. (See pic)
3) When I disassembled the engine to clean it, I messed something up. It does seem to sound different...here's a link to a video of me running it. Does it sound off to anybody else?
4) If anybody has ANY ideas, please let me know, it'd be appreciated.

1)

2)

Newbie to these engines, don't know what valve clearance is, and I can't really describe in words how far I stripped it down. I didn't do too much, I took off the outer shell, took the muffler off, got the staton friction drive off to reveal what I believe is the clutch, took the pull start off, and some other stuff can't remember exactly. TBH I wasn't exactly sure what I was doing.

Here's a pic of it when I was cleaning.


BTW I was using 3-in-One to scrub off the rust and it got everywhere, might that have damaged the engine?

What I've decided to do (and I wish I thought of this at the start of the weekend), if I'm going to take the engine off my Fito Modena and put it back on my old cruiser and see if I get the power back. If I do, then there's something wrong with the Fito and/or how I'm mounting. If not, then somethings wrong with the engine...

I'll post my results when I get the chance.

Update: The motor oil change, and a flusher mount of the engine gave me much better results!

Unfortunately, one of my engine mount plates is now slightly bent because I Torque'd down the middle nut too much...