On the rear axle there are tire alignment bolts that you can move the tire forward and backward at small marked sections. all you need are and couple of small wrenches maybe 8mm or 10mm
Just make sure that you move both sides of the rear tire the same amount, so your rear tire stays true with the front.
you should get a shop manual but here goes, first the back tire needs to be off the ground so the tension is off the chain. next with some nail polish mark both adjustment nuts so you know when they have turned half or full turn.ther are two nuts because one locks the other,so release the locking nut so you can begin turning the actual adjusting nut,go a half turn on each on at a time untill you reach the desired chain tension then relock the nuts and your done.
On the rear axle there are tire alignment bolts that you can move the tire forward and backward at small marked sections. all you need are and couple of small wrenches maybe 8mm or 10mm
Just make sure that you move both sides of the rear tire the same amount, so your rear tire stays true with the front.
If it was me, I would just get a new set of chains for something that old.
First thing would be a Haynes (or similar) manual. It will show you how to do the job and what tools you need.
you should get a shop manual but here goes, first the back tire needs to be off the ground so the tension is off the chain. next with some nail polish mark both adjustment nuts so you know when they have turned half or full turn.ther are two nuts because one locks the other,so release the locking nut so you can begin turning the actual adjusting nut,go a half turn on each on at a time untill you reach the desired chain tension then relock the nuts and your done.