I pulled a 1085 Team Fuji out of the pile at the Bike Exchange to work on a couple weeks ago. I decided to get rid of the drop bars and put 2" riser bars on instead. I also put on some sexy black wheels and a 11/32 Sunrace cassette with a Sunrace trigger shifter and a Deore lx rear derailleur. I removed the front derailleur and 53 tooth chain ring keeping the 42 tooth inner ring. When I went to install the chain I wrapped it around the 32 tooth cog and 42 tooth ring. When I laced the chain around the rear derailleur it was way too short. I wound up adding 6 links to the chain to get it to look and work right.

Can someone tell me where I screwed up?

Sounds like when sizing the chain the first time you forgot to accommodate the amount needed to weave through the der. Or is this too simple an answer? IIRC the bike came with SunTour ders stock. If so then the der likely doesn't have a sprung upper pivot (the B pivot) and the pulley sits as far below the cogs as is needed to have the upper pulley clear the 32T cog and won't pivot up unless the B screw is employed. What we also don't really know is what the der's cage length is. A longer cage will require more chain. Andy

I use this method, always seemed to work fine for me: Derailer Adjustment

When sizing a chain I use the big/big method: Wrap the chain around the two biggest sprockets, figure the shortest place you could join the chain and add 1 inch (2 links) of chain to that. That yields the shortest chain that you can safely use with that gearing combination. Surprisingly, the length of the derailleur cage doesn't seem to matter because, when you're in the big/big, the derailleur cage is pulled nearly horizontal so the lower chain run is almost straight.

It sounds to me like you initially forgot to add the two additional links and then adjusted by adding more links than you really needed to add. I doubt it will matter because, with only one chainring, your chain wrap needs are relatively modest. I'm thinking you're good if you ever decide to switch to a 36 tooth rear cog.

I guess i'm only familiar with Shimano and Campy rear derailleurs where bypassing the rear derailleur and wrapping only big-big+1" sizes the chain properly. If older Sun Tour derailleurs are different, I'm not aware of it.