http://www.pbresource.com/springkit.html

On my Cowpoke (and Diamond Jack), the Roto would spin, then not spring back
a bit, as it should, when it stopped, thus mis-aligning the wiper blades with the
wiper board's rivets. So as I did when I first went through the machine, I removed
the spring loaded wiper, cleaned the wiper board, and applied a film of light weight
grease. I myself then like to apply a thin film of Remington Gun Oil over
the grease to thin it out a bit. This will make the wiper spin more freely, and
when stopped, notch back just a bit and place itself squarely on the wiper board's
rivets..
While the wiper is off, I also like to put a couple drops of Remington Gun Oil in the
spring loaded wiper holes to make certain that the spring loaded wipers has no
stickiness and are able to move freely..

Also people like to set the disk low on the spindle to ensure good contact and will cause too much drag. Ensure the disk mounting is not too close, you'll want the wipers mostly extended. As the previous post mentioned cleaned and lightly lubed to get it spinning freely is a must.

The long spring does help to return the roto to the rest position. On many games I'll see this shortened putting a lot more tension on the return but this cuts down the spin...

I have also replaced 2-3 spindles on these games, for 1 reason or another these can get bent which also causes a bad return. If I suspect a spindle I'll remove it from the roto and put it in my power drill. You can see very quickly if this is out of alignment. PBR also sells these.

You may just need to adjust the disc if it’s just off on alignment. Also, if you want to get a spring kit I might have one but have to look.

http://www.papinball.com/tips/GTB_roto_adjustment.jpg

Check it out.