No Machining! Easy Installation! Stock Looking!

Despite what some say, bigger is better, and if making something bigger is easy, that’s the best!  A big bore kit is an easy way to achieve more displacement, and if you can install it without rebalancing flywheels or boring the crankcases, that’s about as easy as it gets.  That’s the idea behind the new S&S® 97" big bore kits for 1999-’06 big twins and the 106" big bore kits for 2007-up big twins.  No need to bore or even split the cases, just do the cylinder and piston swap. In addition to the ease of installation, they look great because the cylinders are available with the same silver or wrinkle black powdercoat as stock, so they match the stock finish of your engine.

At 3.927" bore, these cylinders have the largest bore that we feel can safely be used in a cylinder with stock spigot diameter.  In fact, this kit is only offered with S&S cylinders because, even though stock cylinders can physically be bored to fit the 3.927" pistons, we are not confident that the material used to make the stock cylinder liner and spigot is strong enough.  The cylinder liner material in S&S cylinders is much stronger, and has proven its ability to stand up to the added power in numerous dyno pulls, street miles, and a lot of quarter mile drag strip runs.  There is a trade-off for the ease of installation, which is that only one piston oversize is available for this kit.  This really is as big as we are willing to go with a stock diameter cylinder spigot.

Go Fast, Look Stock

"Pretty fast for a stock bike, brother!" That’s a comment you might hear when you’re running an S&S® 97" or 106" big  bore kit with our new, redesigned and retooled cylinders. We’ve made a host of changes to improve the strength and cooling capabilities of our big bore cylinders, but best of all we’ve made them cosmetically difficult to tell from stock Harley-Davidson® jugs. Upgrade your ride with more displacement and power, but don’t let anybody know!

This design change carries over for all S&S cylinders for 1999-2012 Harley-Davidson big twins. S&S also offers cylinders with 3 7/8" (for 95" and 103" engines), 4", and 4 1/8" bore sizes. Cylinders for S&S 4 1/8" bore V-series engines also share this new design.
This dyno chart compares a stock 96" 2009 FLHT on the same bike with an S&S 106" Big Bore Top End Kit with CNC ported heads, S&S slip-on mufflers, performance intake, and two different cams. The middle curves represent the 106 with S&S 551 touring cams and S&S teardrop air cleaner on the stock 50mm throttle body. Great torque for performance touring applications. The top curves show the S&S 585 cams with a 58mm throttle body. The increased duration of the 585 reduces low and midrange torque, but the combination of more aggressive valve timing, higher lift and a larger throttle body significantly increases usable rpm and top end horsepower. A good choice for lighter bikes and racing applications. Both engines were tuned with Dynojet® Power Vision® Tuner.

97'' Big Bore Kits For 1999-06 Bt

Silver Powdercoat Finish       910-0201
Black Powdercoat Finish       910-0205

106'' Big Bore Kits For 2007-up Bt

Silver Powdercoat Finish       910-0202
Black Powdercoat Finish       910-0206

Performance Recommendations

These big bore kits yield excellent results with stock cylinder heads, but a performance cam is recommended to get the best performance.  To make the engine easier to turn over at start-up, we recommend the S&S Easy Start cams with built-in compression releases.  For the absolute best performance, we recommend S&S cylinder heads with increased head flow and resulting power increase.

S&S 97" and 106" Big Bore Kit Specifications
Bore Model YearStroke
DisplacementCompression Ratio
Stock HeadsS&S 89cc HeadsS&S 79cc Heads

2007-up4 3/8"106"10.2:19.8:110.8:1


  • For most applications, we recommend the S&S single bore EFI throttle body with a teardrop air cleaner or tuned induction. 2008-up touring models will need to use the stock intake or Screamin’ Eagle® 58mm throttle body and Race tuner orPro EFI Super Tuner.
  • New design cylinders have new part numbers. However, for the convenience of our customers, old part numbers will automatically supersede to the correct part numbers for the newer style
    cylinders when placing an order.
  • If replacing one original design cylinder, replace both cylinders, so they cosmetically match.

Not legal for sale or use on EPA or CA pollution controlled vehicles.