Ok, I'm on a 2001 LX. I just put in an Airsal head and piston and wearing an old Bi-Turbo. I just put on 2 new sprockets and a chain. I also just changed the tranny oil. All in the last couple days.
Ok -- the new sound: it sounds like it is coming from the cylinder area (it runs in time with the engine, not the tranny). It sounds like the noise you get when you put a baseball card on a bicycle, a bit lower in tone, but the same flippy metallic type sound. Again, as the throttle revs, it increases in time.
I'm already paranoid the oil pump isn't working so I put in more oil into the tank (that's why the Airsal went in, I burnt my last cylinder/piston on a no oil condition). I pulled the head and it doesn't appear like anything is scratched.
What could it be and how can I diagnose it properly? Can the reed valve make that much noise? The intake came loose during the time (and I heard it and correctly guessed a loose intake) -- can the reed become damaged getting loose?
Is it something externally rattling (it is fairly noisy at low RPM, can't hear it at speed, exhaust too loud). Tell me what I sound pull and how to inspect and I'll give it a whirl.
If you correctly guess this sound -- I'll send you the wrist-pin from my damaged piston/cylinder combo! Good luck!