Thanks to info from this forum and with tips from Capt. Bike (RIP) I was able to change my 6 speed 13-23 Uniglide cassette to a 13-28 (13-15-18-21-24-28) which my Dura Ace 7400 rear derailleur works fine with.

My bike came with a set of 53-42 (130 bcd) front rings which I am changing out. I have a new 38 and I am thinking of a 48 or 50 outer ring. What would you suggest?

I have also been contemplating trying the cassette ( I have enough cogs) as a 13-15-17-19-21-28 with the 28 being a bailout gear. I am not sure how well the RD will handle a 7 tooth jump. What do you think?

Thanks

What bike are you doing up??

It is the "Murray". I figure that since it was built as a climbers bike I might as well try and climb with it

PS: Crazy action on the Vancouver Craigslist lately. A week ago a full Super Record early Eddy (old graphics, flat crown, light metallic blue) for $299 and last night a mid 80's De Rosa (SLX, full C Record) for $199. I am staying with my current stable right now but I almost bought the Eddy for you without asking you first because I know that I could pass it along if you didn't take it.

Why not buy a 7-speed Hyperglide cassette, and file or grind away the rogue wide spline on the sprockets? They're not too expensive. You could use your 13-tooth (threaded?) Uniglide sprocket, rather than the sprocket+lockring that it comes with, to finish it off. Seven gears makes it easier to have a sequence without large jumps at the bailout end.

I would have taken either of those!!!

I used the Hyperglide cogs from a SunRace 7 speed cassette so I could use those 6 and spacers and my Uniglide 13 if I want to run 7 speed but I don't have Dura Ace 7 speed shifters and I want to keep the bike as close to original as possible.

I started experimenting with custom cog sets early this year.
My initial combo was 13-14-15-16-17-19-24.
I have friction shifters, and when I "erred" between the 24-19, I had a nasty "crunch, ping" sound. Going to a 19-23 made a huge difference. I don't get the "ping", and the 'crunch" is less severe.
Maybe I'm just shifting better since I'm not shivering?

IF you only use the 28 as a bailout gear AND shift GENTLY, you should be OK. Else, your "ping" may be a "PING"!

EDIT: I just remembered- My initial set up was 19-26 that "pinged". I only ran that a couple days before dropping the 26.