Pictures help. Typically when deciding how much money to sink into a machined hole, I look at a few things.
1) top cylinder ridge: Where the top sompression ring stops at TDC in the pistons travel is a heavily worn are for a number of reasons we won't go into. If you see a noticeable ridge above this area, one you can catch your fingernail on especially, it "needs it" (a new bore and oversized piston). This ridge is usually most prominent at the 12 and 6 o clock positions of the piston, in relation to the centerline of the crankshaft/rod
2) scoring/pitting: Thouh caused by two (or more) different things, scoring, pitting or chipping (typically nikasil and not usually here) of the cylinder wall is a sure sin you need some professional help. A vertical groove in the pistons up and down travel prevents the ring from seating correctly and is a sure site for loss of compression and oil consumption. Pits or chips will do the same, and I've even seen in extreme cases (typically 2 stroke) issues where the ring can become hung up on such and area and damage the ring land, rings, and cylinder all at the same time. This is a sure fire way to send a cylinder to the scrap yard and will possibly even lock the rear tire as you practice your unicycle skills. Needs it for sure.
3) cross hatch: even with light rust staining, assuming the top two factors ARE NOT present, look for the original cross hatch in the cylinders. The hatch is only about a half thousandth (.0005") deep, maybe less, and if they're present on all surfaces, you might just be able to rebuild on the cheap (i.e. A finish hone and a set of rings). Maybe a piston if the other is less than perfect. The ,achinist can usually determine this for you. Even on cars with 100k+ miles, I've seen these marks present. If they're missing in easily distinguishable areas, the cylinder is likely oblong or out of round, and then, needs it.
Hope that helps. Buen suerte!
