If you’re the proud owner of a Harley-Davidson Milwaukee Eight big twin, but you’ve been waiting for S&S to come out with just the thing to boost your power, the wait is over. S&S Cycle just introduced its new 131 cubic inch stroker kit, suitable for all your M8 power-enhancing needs. 

As you’d expect, the displacement increase also amps up both horsepower and torque. How much difference does it make? According to S&S, swapping in this kit along with its 4.625-inch stroker crank (sold separately but required for installation of this kit) on the stock 114CI unit in a Street Glide resulted in significant gains. Stock, it produced 81.07 horsepower and 111.71 ft-lbs of torque. By contrast, the S&S kit unleashed 146.62 horsepower and 145.45 ft-lbs of torque.  

What’s in the kit? New design forged pistons are paired up with S&S’s 4.25-inch cylinders, along with piston rings and .045-inch multi-layered steel head gaskets. You also get a 131 cam cover badge if you want to show your work—or you can leave it off to keep it stealth. “We build our big bore kits and cranks to much tighter tolerances and with higher quality materials than the factory parts,” project manager Grant Hilligass said. 

S&S 131 Big Bore Stroke Kit Components
S&S 131 Big Bore Stroke Kit Chart

S&S also prides itself on offering your choice of looks to match your particular aesthetic, with powder coats to match the factory finish. This kit works with the stock crankcases, and also retains stock engine height. It’s available in your choice of Wrinkle Black with or without highlighted fins, or Black Granite with highlighted fins.  

MSRP for all three variations on this kit is $1,299.95. Installation also requires the 4 5/8-inch stroker crank, sold separately at an MSRP of $1,529.95. If you’re looking for a winter project to help take the sting out of months of hibernation, this could be it.  

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