Article And Photos By: S&S Cycles
Originally Published In The April 2014 Issue Of Cycle Source Magazine
Last month, we took Ryan’s 2009 Harley-Davidson® 883 Sportster® from the stock 45 horsepower to 56 horsepower just by installing S&S slip-on performance mufflers and an S&S Stealth air cleaner with an Airstream cover. We also loaded an S&S EFI tune file into the ECU with a Dynojet® Power Vision Tuner. The tuner wasn’t an absolute necessity for an exhaust and intake installation, but we knew we’d sure ’nuff need it for what we’re doing this month. The message here is that if you are starting with the usual slip-ons and air cleaner, but plan on doing more, you might as well buck up and get a tuner now. That way you can get the most from your initial performance investment, and you will absolutely need it when you increase displacement or change Article & Photos: Compliments of S&S Cycle cams. This month, we’re going to throw the cubes to her and install an S&S 883cc to 1200cc conversion kit. Bigger is always better! Right?
The installation of the cylinder and piston kit is pretty straightforward. It’s like doing a top end job on a stock engine only you don’t have any machine work to do because the pistons come already fit to the cylinders in the S&S 883cc to 1200cc conversion kit. So essentially it’s a cylinder swap. Any competent mechanic can handle it with ease. We didn’t absolutely need to do it at this point, but we installed a set of S&S Quickee pushrods. That’s because we plan on installing a set of cams later, and we don’t want to have to take the rocker covers off again. Not lazy, just efficient!
The pistons in the S&S 883cc to 1200cc conversion kit are designed to be installed without rebalancing. In fact, it’s interesting to note that a quick check of the parts’ books reveals that current 883cc and 1200cc engines use the same flywheel assembly, so there is no difference in the balancing. That makes it easy.
“Now wait a minute! Aren’t you going to change the cams?” you may ask. Not today. We’ll talk about that in a future article. The parts’ book also reveals that the cams in current 883cc engines are the same as in the 1200cc, and they’re really pretty good cams. So we’ll keep the stock cams for now.
One thing that we did do was to upgrade the clutch. We’re not talking about a mega-bucks full replacement. We just installed a stiffer Barnett clutch spring. We also performed one other preemptive maneuver. We pulled half the plates out of the clutch, while we had it apart to change the spring, and removed the jutter spring from the middle of the clutch pack. The jutter spring is a couple of steel plates riveted together with some bent steel wave springs sandwiched between them. It’s there to cushion the clutch pack and make the clutch engage more smoothly, but with additional torque and horsepower, the jutter can come apart and cause no end of aggravation. We replaced the jutter spring with two stock steel plates and one fiber disc. That makes up for the thickness of the jutter spring and adds some friction surface to the clutch pack. Bonus!
We are still using the stock 883 heads on this engine, and they are different from 1200 heads. The combustion chamber is smaller and the valves are smaller. That’s why the pistons have a slight dish in the domes, to keep the compression ratio down to a reasonable 9.4:1. The smaller valves tend to limit high rpm horsepower somewhat, but they also tend to improve low and midrange torque. We loaded a special Power Vision calibration file for 1200cc engines with 883 heads. It’s available for free on the S&S website (www.sscycle.com/tunefiles/ power-vision).
So what did Ryan think when he took it for a test ride? It was pretty obvious that something was up as soon as he hit the starter. The engine had a different sound, a bit more bark…but what about the bite?
Ryan took the bike out on the back roads around Viola, WI, where S&S is located, and as soon as he was out of the driveway he grabbed a handful of throttle. The result must have been pretty satisfying because he kept it up for quite a while. Sound travels quite well in these hills, and we could hear him winding through the gears on these curvy, hilly roads. It was pretty obvious that he was having a great time. When he got back, he again said he was amazed at the difference in power from the last time he’d ridden the bike. He’d been amazed that time too. We had to caution him that the first two steps are where we get the really big performance increases. In this step, we raised the bar from 56 to 69 horsepower, but keep in mind that the stock engine only made 45. After this, the gains will not be as dramatic. They’re there, but we have to work a little harder for them. Ryan’s reaction, “I can’t wait!”
Next month, we make better use of our increased displacement with a set of S&S bolt-in cams!
This photo shows the difference between the stock 883 piston and the S&S 883cc to 1200cc conversion piston. The stroke for all Harley- Davidson® Sportster® models is the same, 3-13/16”, but 883cc engines have 3” bore cylinders compared to the 1200cc engine’s 3-1/2” bore cylinders. Since this is a conversion piston, meant to be run with stock 883 heads, there is a dish in the top of the piston to keep compression in a reasonable range.
S&S pistons are installed on the stock connecting rods. This engine only had about 1200 miles on it, so the rod bushings are perfect. In spite of the larger bore size, no rebalancing is required.
Once the pistons and rings are in place, the cylinders are installed with a ring compressor. This is all standard engine assembly procedure. Note that the black wrinkle powder coat finish matches the finish on the crankcases perfectly.
We upgraded the clutch with a heavier spring, and while we had the clutch apart, we removed this jutter spring from the clutch pack. Under increased torque and horsepower, jutter springs can come apart and cause problems. We’d rather have some extra friction surface anyway.
To make up for the thickness of the jutter spring that we removed, and to gain some additional friction surfaces, two steel plates and a fiber friction disc were added to the clutch pack.
The Dynojet® 250i tells the tale. The lower curves of this dyno chart show the output of the stock 883cc engine. The upper curves show the results from the same engine with the S&S 883cc to 1200cc conversion kit installed. The upgraded engine also was equipped with the S&S slip-on performance mufflers and S&S Stealth air cleaner that we installed last month.