S&S CYCLE Super Stock Engine Case for Evolution Big Twin - 3.500" Bore, Part 31-0000 Hardware Group the main springs feature a

the main springs feature a progressive rate tailored for the demands of long-distance riding

EXP bases (two halves) for reliable operation

especially for bikes operated at or near maximum load ratings more than 50% of the time

providing significant power gains

allowing each to compress independently

S&S CYCLE Super Stock Engine Case for Evolution Big Twin - 3.500" Bore, Part 31-0000 Hardware Group the main springs feature aEngine Case Super Stock 3. 500" Evolution Big Twin The S&S CYCLE Super Stock engine case (Part 31 0000) is designed for high performance Evolution Big Twin motorcycles with a 3. 5 inch bore. Crafted in the USA, this engine case is engineered to accommodate any stroke up to 5 inches and most stock length connecting rods, providing versatile customization for your build. The case features precision machining to accept an oil filter assembly that mounts