bandsaw spring

[Ben Kann]

I'm a new member with an old bandsaw (Power King 912) with a 1/2 hp "Power Kraft" motor and a tired bandsaw spring. I tried to replace the spring with a 2-1/2" Iturra(sp?) but the post it's on is also 2-1/2" and I can't compress it enough to put the tensioning knob back on. Is there some technique for this or am I using a wrong part? And if it's the wrong part, where can I find the right one?
Also, I'd like to upgrade the motor to something larger. What's the max I can safely hook up to this machine?
Nice to be here. I hope to learn a lot from you guys.
Ben