I have a 620 like yours. You'll have a great bike when you're done. Your paint is nice. It's amazing in the sun.
My experience is similar to the other posts:
- Yours is an '84. The cantilever brakes and all your components match the Trek catalog specs. The chain stays on the '84's are longer than the '83's which is usually a better geometry for touring bikes (45. cm length vs. 44)
- The derailleurs are smooth and mostly trouble free. (I have a 620 and 720. Both shift well. However, I had another 620 that jammed the rear derailleur when the bike was rolled backwards too quickly. It was still rideable as long as you were careful when moving the bike Others have the same problem. Search the forums for more info if you have that trouble.)
- Helicomatic hubs are smooth but some had pitted cones. My front wheel was pitted, but I kept them because I couldn't find replacements.
- I eventually got another wheelset for my 720 so I could use standard thread-on freewheels. Shifting on the stock freewheel was poor compared to Suntour and Shimano freewheels. I got tired of fussing with each shift. Also the original freewheels were worn. Replacements are hard to find and expensive.
- Overhauling the pedals is easy.
- The headset uses roller bearing instead of ball bearings. I wasn't good at adjusting them, but once I got it right they work very well, and are sturdy.
- Ratcheting Suntour shifters are great. The downtube Sprints are smoother and more precise than Suntour's other models. (The Sprint 9000's are also an option. They can be set to indexed or friction).
- Vintage Trek is an incredible site about steel Treks. Serial number charts give the exact day the bike was built. Also catalogs, history and much more.