Blake:

Rinsing out your old Svea 123R with fresh fuel may be enough. I'd drain it, flush it, fill it 3/4, and then let it sit a while before trying to light it.

I'd also see that the valve turns smoothly and that the gasket in the tank cap doesn't have any cracks and still has at least some pliability. If the gasket is cracked or hard as a rock, you'll need to replace the gasket.

Be really careful of course when firing up an old stove. Do it outdoors away from anything flammable and all that.

HJ