Of course! Its part of cycling. Help others, others help you. Its a beautiful thing.
Doesnt have to be a mechanical to help out either. A few years ago I greeted a cyclist as I passed him. I had just started my ride and was fresh. He, I could tell was struggling. We had a brief conversation. He was in over 60 miles for the day and was another 10 miles from home. I said I was going that way and would be glad to pace him for the distance. He sat on my wheel drafting as I set a steady easy pace. If he drifted back I slowed down. He was very appreciative of the support. I was happy to assist.