I get asked about the Fostex R8 almost on a daily basis , so will put this here as it will solve about 80% of peoples problems
The R8 uses two reel motors on which both have pressed on them a black plastic pulley, it relies on being pressed on there is no locking pin etc.
Many people have been using sticky old Ampex tape or just using their machines a lot.
In the end the pulley starts to slip, it may work half way through the reel and then slip or it will not work at all forward or backwards.
The main solution to this is get a new pulley (some man in Italy was making a 3D printed version), or to reglue it.
Take the pulley off, get a bit of plastercine whatever and make a slight depression in it say with a marble, then put the plastic pulley on top and pour the hardest liquid cement/plastic in the central hole, leave over night, then drill a hole a bit less than the spindle on the motor, push the pulley back on. some people add a dab more cement when its on to flow over the shaft.
There should be a nice round bump on the end as it went into the depression of the marble
That normally solves the problem but it will appear again later if you continue to use old tape.
It might be worth me maching up some ali ones but there probably is not the demand now.
Let me know how you all get on
At great expense I have ordered from an old watch and gear factory some new metal pulleys to be made they will be all metal and have a bush at one end, they are due in Mid December 2017
I have seen the ones made by 3d printing and they work but not for long, these new pulleys will solve this problem once and for all, though now you may burn the motor out :-) dont use old tape is the moral here