I've recently acquired a Schwinn Mesa Runner MTB. My dad purchased it new in the late 1980s, I think. I'm setting it up as an around-town utility bike, possibly a single speed. I'm interested in replacing the cranks for two reasons:
1. I wanted to replace the nylon pedals with some NOS metal pedals I found at a junk shop. However, one of the pedals is rusted to the crank arm. The other one came off fairly easily, but I cannot exert enough force to remove the other one.
2. I would like the ability to experiment with different sized chain rings. The current chain rings are riveted on, making replacement impossible.
1. I presume that this bike has a square spindle bottom bracket that will accept modern cranks. Is this correct?
2. Could anyone recommend a low cost replacement crankset? I'd like something basic, but durable. And, again, I'd like to be able to change chain rings.
You're probably better positioned than we to know whether the BB has a square shaft. You should be able to see it without even removing the cranks.
As for a replacement if it does, you might consider the older Shimano Deore LX cranks. I'm not sure whether the newer version has removable rings. There are several older sets on ebay as this is written.
P.S. You do know that left pedals are reverse-threaded, I assume? If that's the one that is giving you problems, are you turning it the right direction?