What he said, Skirk.
And Chainsawgang (can I call you "gang"?) -- the capacitors you need to install are disc ceramics, which aren't polarized at all, meaning that you can connect either lead to either the positive or negative terminal and the other lead to the other one. You want to get right at the terminals at the motor.
Start with a 0.05 microfarad capacitor to see if it helps. Then add another one, OR add a 0.1 uf. Each installation is different, and you pretty much have to run it by ear, literally. I have a capacitor substitution box that I use quite a bit. Problem with that is the lead length. You need to keep the lead lengths as short as possible. When adding more capacitance doesn't change things any more, you can either leave things as they are OR you can total things up and install just ONE capacitor somewhere near that total value.
Use capacitors rated at least 35 volts DC. Most disc ceramics are rated around 200 volts, so you're good to go there; just check the package.