Well...first thing is you should have bought proper belts from Martin Olsen (Dillen here on the forum).  At the age of a Beocord 8000 it would need both belts and rubber wheels. The cassette mechanical assembly needs to be cleaned and lubricated. That can all be done while replacing the rubber wheels. There is a clutch arm part that one rubber wheel fits to that is typically cracked. 

Depending on the environment the Beocord was stored all of these years it could probably benefit with replacing its electrolytic capacitors. The fact that it does still try to play is a good sign of course.  Keep in mind that many of these vintage audio components will still work even when parts are way out of tolerance. If a proper restoration isn't performed you won't really be experiencing the full capability of the component.

I'm not trying to be negative here but I think a lot of buyers set the expectation way too high regarding the ease of getting vintage audio components working properly again. Most items sold on Ebay are units that are not restored and require quite a bit of work. 

-sonavor

I bought the belts off ebay UK which were specifically for this model - the seller had a high rating so I'm confident the belts are not the issue.

So I opened it up and with a tape inside fiddled a bit - I figured that if you push both rods up into the left and right solenoid thingy at the same time that is play and the tape starts to play.  From looking under the mech, if you pull the right solenoid rod down (thus the left goes up), that is high speed reverse which is does.  Thus if you push the right solenoid rod up (and thus the left rod down) that should be high speed forward though when I do that nothing happens.  So my question - what specific item would prevent this high speed forward when I push that right rod up?  Is there a separate motor for each reverse and forward?  Is there some relay or fuse for each?   Is there a unique belt for each?   Thanks

There is only one motor. The functions are selected using solenoids and rubber idlers.

I suggest you replace the idler wheel rubber parts, clean and lubricate.
New correct belts and idler rubber parts will see most of these drives back in perfect operation again.

Correct parts can be found here: