Wii Unable to read Disc repair help

Hi. I recently bought a 'broken' wii off ebay and my plan is either to to repair it and sell it or repair it and sell my original. Which I do depends on just how repairable the problem is.
The wii gives "unable to read disc" error on the disc channel for all wii games that I've tested (Wii play and Wii sports.) When starting up there is an unusual sound from the disc drive, kind of high pitch screech/squeak though quite quiet. The same noise is heard when a disc is placed just inside the disc drive so that it starts the motor inside the wii to pull in the disc but the disc is not in far enough to be caught by it.
Interestingly, I have tested several gamecube games and although most won't work, I managed to get Resident Evil 3 and Resident Evil 1 disc 2 (took several tries) to load. I didn't bother going past the new/load game screen so I suppose it's possible that they might crash if I attempted to play them any further. I have plenty of Wii and Gamecube games so if it would help with a diagnosis of the problem I can test them all and post back which ones worked and which ones didn't.

Judging from the strange sound I can hear I think something inside the disc drive has been moved slightly out of place and is scratching against something else. Though I'll point out that this noise is only heard when a disc is being taken in so I'm not sure how it would prevent the wii from reading a disc that is already in. If that is the problem, then taking it apart and examining the disc drive for out of place components and giving them a jiggle would probably be a good start. Cleaning the lens wouldn't hurt either I'd bet. If those solutions don't work, my next thought was to simply replace the dvd drive as the wii appears to be fully functional otherwise. I was thinking about getting the sundriver dvd replacement that reads isos off a hard drive and installing it in the 'broken wii' and selling my original, fully functional one in that case.

Does anyone have any thoughts or suggestions as to what might be causing the 'unable to read disc' error and how to repair it? Everything I've said is complete guess work, I've never taken apart a wii before so I'm really just going on what I've managed to find out on google. If anyone agrees with my thoughts that taking it apart and giving it a jiggle would be a good plan some advice on what component most commonly goes out of place and what to look out for would be nice.
If it makes a difference the wii is on firmware 4.1E.

 

I've taken the wii apart and had a little play about with it whilst open. It seems that when the wii gives the unable to read error it's because the wii hasn't even attempted to spin the disc. When it does spin the disc it is able to read just fine. Is this the cog problem you guys suggested? I'm going to have a google about and see if I can find any similar problems or methods to fix.

 

So I've fiddled about and no luck so far. I took the top casing off the dvd drive and gave the insides a hoover to see if it made any difference but no luck. A google search didn't prove very helpful either. So I'm all out of ideas now. I'll recap what the problem is and if anyone has an idea for a solution let me know please:

Disc is able to be inserted
Wii makes usual click noises for inserting disc.
Wii WILL NOT spin any wii disc and a few seconds later "unable to read disc" error appears.
Wii WILL spin certain gamecube games after several attempts, but not all.
Upright and flat positions have been tested and no difference found.
Disc has been manually rotated, so there is nothing physically preventing the spinning.
Wii is system menu 4.1E

Considering that the wii will accept, spin and run gamecube games I don't think it's the lens that's the problem. Also, as the disc can be manually rotated it's not the spinning mechanism that's the problem. My only thought is that whatever method the wii uses to check if the disc is a wii or gamecube disc is faulty and failing to provide a meaningful result for all wii games and a tempermental result for gamecube games. I've no idea how the wii checks what kind of disc it is, before today I'd always thought it would spin the disc first before checking. Whatever it is I seriously doubt it's a physical check, most likely some kind of circuitry is involved in which case the easiest repair would be to replace this circuitry. If that's the case then I'll have a look about ebay or whatever to see how much this replacement costs (though I'll have to find out what circuitry piece it is) but most likely I'll give up on it and get the sundriver replacement instead.