It's not the size of the crank, it is the number of teeth on the chain ring that is going to help you with this problem. You could change the crank to something lighter but Sugino make good cranks. You need to find out the BCD of the ring, which is the bolt circle diameter diameter. Google it and there are ways to measure it or take it to a bike shop and ask. Then find the same size BCD ring with the number of teeth that you think might work. Without making this overly complicated by using a gear chart, my guess is a chain ring between the sizes of 40 and 45 would give you the range you need. I would say closer to 40 than 45. There might be issues of fit but I will let others chime in about that.