Originally Posted by graemejones

I just found a 1987 Miyata Omnium bike in my attic. The bike has low mileage because it was used as a stationary bike for all its life. It looks good but the gearing shifts into the next gear when ride in a certain gear. Its only on one of the speeds but I was wondering if there is a simple way to fix my that without having to pay money for a tune up at the bike shop? It's a shimano 600 gearing system just in case that helps .I am short on funds hence why i am riding the bike in the first place.