S&S 89″ EVO Stroker Build Part One

S&S 89" EVO Stroker Build

(Step 1) Here’s the right half of our 1998 EVO-powered Road King’s crankcases. Note the area that the crew at S&S machined out of the inner face of the crankcase. This was done so the new stroker flywheel assembly has the room it needs.

By Chris Maida/ Photos Courtesy of S&S Cycle

Though it doesn’t say so in the headline, this two-issue engine build is part of our ongoing series on rebuilding a 1998 Road King from front to back. The reason for this series is simple: some of our readers prefer a motorcycle without all the electronics of a modern bike, which means they’re looking to buy and rebuild one of the Evo-powered Harleys of the late 1990s. To that end, we’ve been slowly rebuilding and upgrading a 1998 Road King over the last several months. In this two-part series, we’re going to rework the bike’s engine.

Though a stock or worked 80″ Evolution is a good engine, we wanted to kick it up a few notches while still keeping the engine dependable. In fact, this engine was just that: a worked but tired 80″ with a hot cam, SE heads, and a S&S billet oil pump. The bike’s owner requested more cubic inches so he would have no problem keeping up with his Twin Cam-powered buddies. Having used S&S Cycle parts in my high-performance bikes for over 40 years, S&S was my go-to company for an 89″ stroker kit with a matched set of supporting performance components. When making a major modification like a stroker kit, the engine’s other performance components need to complement the upgrade, so that you end up with a strong running and trouble-free engine. Let’s talk about those flywheels first.

S&S 89" EVO Stroker Build

(Step 5) Once the new connecting rod bearings have been fitted to the new S&S crankpin, the flywheels, connecting rods, crankpin and all the bearings and their cages are assembled.

The flywheel kit we stuffed into our stock H-D crankcases is one of S&S’s 89″ Stock Bore Stroker Kits for 1984-99 Carbureted Big Twins (#32-2230/$1,134.95). What all that means is we reused the stock H-D cylinders, but we swapped out the stock 4-1/4″ stroke flywheels for a set of S&S 4-5/8″ stroker flywheels. Increasing the engine’s stroke, which is how far the pistons move up and down in the cylinders, increases the engine’s displacement. With these 4-5/8″ stroke flywheels, the pistons move 3/16″ farther up and 3/16″ farther down the cylinder’s bore, which increases the engine’s total size by about 9 cubic inches! In any engine that will result in a nice power boost! And though this setup requires some minor crankcase and cylinder modifications (mods that can easily be done with hand tools), just swapping out the flywheels for longer stroke versions is an economical way to increase the displacement of your engine. This flywheel kit also comes with a set of S&S heavy duty connecting rods, as well as S&S sprocket and pinion shafts, all assembled, balanced, trued, and ready to be installed into a set of cases. Since the pistons will be moving deeper and higher in the cylinders, special pistons, which must be ordered separately, are required but we’ll talk about those in the next issue.

As for the cam we decided to roll with, an S&S 561 (#33-5076/$189.95) was a perfect match for what the owner wanted from his new motor. This cam fits 1984-99 Big Twins and is designed for 88″-96″ engines with a 9.5:1-10.5:1 compression ratio. We wanted the 561 because it produces strong power right in the 3000-5500 rpm range. This is a Road King, not a racing bike. With the cam kicking in at 3000 rpm, the owner can cruise all day long below 3000, which is where cruising is done, without gobbling fuel. But when he wants to pass a truck, get on a highway, etc., a simple twist of the wrist brings the cam in with the resulting boost in power. The 561 requires hydraulic tappets and valve spring spacing, which we’ll also cover in the next issue when we install them.

S&S 89" EVO Stroker Build

(Step 10) The stock left case is then positioned onto the flywheel assembly, so the outer Timken bearing can be pressed onto the shaft. The bearing endplay is then checked using a special fixture and a new shaft seal installed.

As for who would build our engine, we went right to the source: S&S Cycle! The S&S Service & Speed Center will install any product S&S sells onto your engine, as well as rebuild all S&S engines and other products (carbs, etc.). However, they’ll also rebuild 1966 and later Harley Big Twin engines, and 1948-99 H-D Big Twin and 1957-85 Sportster flywheel assemblies, and a whole lot more. We shipped the S&S Service & Speed Center the engine components they requested and what we got back was an engine ready to be bolted into the frame. The accompanying photos and captions show many of the steps S&S takes to install one of its stroker kits into a set of stock Harley-Davidson crankcases. In the next issue, we’ll show you how the top end was overhauled and assembled. – AIM

S&S 89" EVO Stroker Build

(Step 14) Both stock crankcase mating surfaces are coated with ThreeBond 1104 sealant before they’re bolted together.



S&S Cycle Inc.

Like what you see? The full article with all 22 steps, Tips & Tricks, and tools needed, is in American Iron Magazine Issue # 343! To order a back issue of this or any other issue of American Iron Magazine, visit Greaserag.com.
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S&S 89" EVO Stroker Build

(Step 20) The new S&S steel breather gear (note the slotted evacuation hole) gets coated with assembly lube. The engine is then rotated to bring the timing mark on the pinion gear into position.