Vintage Suntour Rear Derailleur

I finally came across a bike with a Suntour rear derailleur. These are a bit strange looking, but they really do shift nice. I took this one apart to clean and lubricate the moving parts, and I'll show you how to do the same. This particular derailleur is a Suntour 7 GT.

You can remove the tension pulley for cleaning with a 9mm wrench:

In order to remove the guide pulley you first have to unscrew the cage stop. It's a little cylinder that keeps the cage from springing too far back:

Next there is a large philips head screw holding the plastic cover over the tension spring. It might be on tight, so make sure you use a big philips screwdriver to avoid stripping it (#3 size):

With the cover off you can see the spring that puts tension on the chain. There are several grooves that the spring can attach to, so you have lots of choices for setting the spring tension. There is also a washer inside that you don't want to lose:

 

  

With the stop unscrewed you can let the cage unwind until there is no more tension on the spring. The spring should now slide right off. You'll want to keep track of where the spring originally clipped onto the pivot so that you can get the correct tension later. The next step is to unscrew this piece:

 

You'll want to use your biggest flat bladed screwdriver for it. This one was really tight though, so I ended up using a small vise grip. The last step is to remove the guide pulley bolt with an 8mm wrench:

That one is pretty tight as well, so make sure your wrench is a good fit on the 2 flat sides. Here is the derailleur disassembled:

Now you can clean everything, oil the pulley bushings, and grease anything else that rotates or slides. Reassembly is the opposite of removal, so keep track of where all the little pieces go. The trickiest part is screwing in the cage stop barrel with the cage under tension from the spring. Rotate the cage back far enough to reinstall the cage stop. You need to hold the cage back with one hand while screwing the stop in with your other.

There's no spring around the mounting bolt to worry about (just like a modern Sram derailleur). Another nice feature is the split pulley cage design because you don't need to break the chain to install the derailleur on your bike.