When you combine our 4 1/8 bore with the stock stroke a 117 is born. We have sold a lot of this combination and it is probably as big as most street engine should go. The pistons retain a decent amount of skirt length on the intake sides so ring life is acceptable. This kit comes with a -10cc dished piston to keep compression in the 10+ range with most heads. This is a large engine and should be built by a pro with experience with these motor sizes. Tuning and good lubrication are critical for long term engine health.

S&S Big Bore Kits


 S&S 97″ and 106″ Big Bore Kit for 1999-Up Big Twins

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 powder coat 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


“WHAT’S IN THAT THING ?”   That’s a comment you might hear when you’re running an S&S® 97″ or 106″ big bore kit with new, redesigned and retooled cylinders. S&S has made a host of changes to improve the strength and cooling capabilities of their big bore cylinders, but best of all they are cosmetically difficult to tell from stock Harley-Davidson® jugs. Upgrade your ride with more displacement and power, but don’t let anybody know!




“Smokin the Competition”

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