My old 100 has a 3-3/8" OD motor pulley & 2 V belts. The new one is 3-15/16" & 3 V belts. Both work fine, but I came very close to putting a smaller pulley on the new 100. It was acting up at first and was more difficult to tune than the older one, but after we got it running right, I really liked the faster speed and harder blows. Forgot about having that large a pulley on the new hammer until just now...
I've seen long V belts on other hammers that track just fine.
Just follow Dave's instruction and you will get it going, especially the sticky ram part and making sure you have the right spring... He knows how to make a LG run right.