Harley-Davidson Evolution Sportster Performance upgrades

Harley-Davidson Evolution Sportster overview

Introduced in 1986 as an 883 and an 1100, the Evolution Sportster is a great improvement on the Ironhead that it replaced. The 1100 was quickly superceded by the 1200 as it rapidly became apparent how strong and tuneable these engines are. The introduction of the 5 speed transmission in 1991, which also involved relocating the alternator from the clutch basket to the end of the crank (like the Big Twins), all but cured any transmission problems. The 5 speed also saw the introduction of head breathers, lifters that run directly in the crankcase, and eventually an upgraded oil pump.

The 2000 models had further significant changes, including a redesigned crankcase that allowed the use of the Twin Cam lifters, and a press fit crank assembly.

2004 saw the introduction of the rubbermount frame, redesigned crankcases and better cylinder heads. For 2007 we waved goodbye to carburettors in favour of fuel injection.

We are great fans of the Evo Sportsters , and we definitely do not consider them to be just a cheap way of acquiring a Harley. Having owned two 4 speeds, two 5 speeds, a Buell Thunderbolt, and an XR1200, we are well aware of their great tuning potential, as well as the many performance upgrades suitable for commuting, touring, or even racing.

Since we have a machine shop, a dyno, and substantial experience with these motors, we can offer everything from an 883-1200 conversion to a complete engine rebuild. We also supply, and fit, (including any machining required) a number of very fast performance upgrades, including big bore and stroker conversions, as well as camshafts and cylinder heads. Tuning, as always, is important, which is why we have our Superflow dyno. The fuel injection models equally benefit from these performance upgrades, and we can, of course, correctly tune these.

Harley-Davidson Evolution Sportster engine rebuilds

With the exception of the 1986 models (which used the pinion bearing from the Ironhead) all Evolution Sportsters require the pinion bearing race to be lapped to size. The current models still use this bearing

86-99 Evolution Sportsters use the traditional taper shaft cranks which can be totally rebuilt. This one, from a 91 1200 has been rebuilt, balanced, and trued

All Evolution Sportster cranks, prior to the introduction of the rubbermount in 2004, use the durable dual Timken bearing set up on the sprocket shaft. This requires the crank to be installed with a service tool

Andrews Evolution Sportster cam gear set, installed in a '91 1200. Installation also requires careful checking to ensure that none of the gears are binding

Totally rebuilt Harley-Davidson Evolution Sportster engine for a customer's Bobber project

Powerglides rebuilt 1200 Sportster engine, installed in a customer's very competently, home built, '91 XL1200 Bobber

Harley-Davidson Evolution Sportster 883-1200 Conversion

Whilst a fine motorcycle in it's own right, the 883 Evolution Sportster is noticeably underpowered, and requires a lot of throttle twisting and gear changing to make swift progress. Converting these to 1200cc by boring out the existing cylinders to suit the 883-1200 conversion pistons that we supply, yields a substantial increase in horsepower, and more importantly, torque. In fact, this popular, basic, conversion gives the most "bang for the buck" of any Harley performance upgrade.

What this translates to in the real world, is far better throttle response, less gear changing, and an excellent "roll on" for safer overtaking.

Many of our customers use their Sportsters for the daily commute to work through heavy traffic, and this conversion is highly recommended for this type of riding.

Carburetted models that already have an acceptable "stage 1" kit only require minor tuning adjustments (we strongly recommend retaining the CV carb), but the 2007 and later, fuel injected models MUST be remapped on the dyno, which we can do here.

We offer this as a ride in, ride out service, and because the machining is done here, we can do this with a short turnaround by prior arrangement. For those customers who prefer to do the work themselves, we can machine your cylinders to our supplied pistons and gasket kit.

And for those that want more, we also offer a number of higher performance upgrades. These use different pistons though, so to save duplicating the costs involved at a later date, we recommend viewing these other options first.

Please note that Harley-Davidson changed the construction of the 883 cylinders in 2009 and these cannot be bored out to 1200. New (or earlier) cylinders will be required.

These are the parts used in our 1200 conversion kit for the Harley-Davidson Sportster 883.

The Wiseco forged pistons are dished to give the correct compression ratio with the small 883 combustion chambers. Their weights are close to that of the original 883 pistons, so crank balance is unaffected. A James top end gasket kit for the appropriate year group (91-03 shown), completes the parts list for most applications. We then bore and hone the original 883 cylinders to suit the Wiseco 1200 conversion pistons. This popular and reliable capacity increase still gives the best "bang for the buck" of any of the Harley performance upgrades.

Performance Cylinder Heads for Harley-Davidson Evolution Sportster

Whilst the regular Evolution Sportster 883-1200 conversion remains the best "bang for the buck" of any Harley-Davidson performance upgrade, there is a lot of additional power to be had by porting the existing 883 cylinder heads. The head castings and existing valve seats have sufficient material in them to allow both the installation of the larger valves from the earlier ('88-'03) 1200 heads, as well as a thorough and well developed reshaping of the ports. The small diameter 883 "hemi" combustion chamber is also used to good effect, as when coupled with the larger cylinder bore size of the 1200 (3 1/2" instead of 3"), a substantial quench area is created. These reworked 883 castings give a far better result than trying to rework the older XL1200 heads, as there is already too much material removed from the wrong places with these.

The next stage on from the basic 883-1200 conversion, is to use Head Quarters ported 883 heads. Whilst the combustion chamber diameters remain unchanged in order to create a useful quench area, they are deeper as a result of machining and blending the valve seats to accept the larger valves. This means that we use Wiseco forged flat top pistons in this application, not the dished pistons used in the basic 883-1200 conversion.

Because the valve stem protrusions remain as stock, and the heads are only decked sufficient to clean them up and balance the chamber volumes, the stock pushrods and tubes can also be retained. Compression can be set between 10.25 and 10.5, and the stock camshafts can also be used. The Sportsters are not under cammed in the same way that the Big Twins are. We recommend the existing 40mm CV carb with a Head Quarters jet kit for the 1986-2006 models, and the stock throttle body and injectors for the 2007 up EFI models. Carb models benefit from one of our programable ignition modules, and the fuel injected models require dyno tuning.

With the introduction of the rubbermount Sportster in 2004, Harley redesigned the 1200 cylinder heads. These are the best XL heads yet, superior even than the older Buell Thunderstorm heads. The valves, combustion chamber, and port design are the same as the Buell XB12 and the XR1200, and they are excellent raw material for porting. Our Head Quarters reworked heads utilise 1.900 intake valves and 1.625 exhaust valves, the same as used with our Harley-Davidson Twin Cam and Evolution Big Twin performance cylinder head upgrades. By using various readily available Wiseco forged pistons and/or decking the heads, we can set compression ratios anywhere between 8 and 12 to 1 with the 1200 engine! This covers any racing or turbo charged application, although typically we will use 10.5 and the stock cams for street use.

These late model Head Quarters ported 1200 Sportster heads can be used with a variety of pistons to achieve the desired compression ratio. Normally, in order to avoid using adjustable pushrods and new tubes, we use these Wiseco forged pistons that a have a dome machined to suit the combustion chamber shape. The late model heads will also retrofit the earlier Evolution Sportster engines, and we most strongly recommend this route to accompany our big bore and stroker performance upgrades.

Stroker and Big Bore Conversions for Harley-Davidson Evolution Sportster

As with all Harley-Davidson performance engine building, we get to the stage where there is, quite simply, "no replacement for displacement". Whilst we can get a substantial power increase from the standard 74" capacity, enlarging the engine by using bigger bore cylinders and even a longer stroke crankshaft, opens up a whole new world of serious performance. The relatively light weight (by H-D standards) of a Sportster, coupled with the massive torque increase that these conversions can produce, give a scarily fast motorcycle.

Sportsters have always been excellent, and relatively cheap, (again, by H-D standards) raw material for those with serious aspirations for reliable high performance. These are not "bolt on" upgrades, and also require reworked cylinder heads, camshafts, crankcase machining, and competent engine building techniques, as well as a decent exhaust and intake system.

Since we have always specialised in this type of work, we can tailor the package to suit any riding style. And with our "in house" machine shop and dyno tuning facility, we can offer any of these higher performance upgrades as turn key packages, including the fuel injection models.

Component parts of an S&S 89" big bore stroker kit for the Harley-Davidson Evolution Sportster. Reworked cylinder heads, camshafts, ignition system, and an appropriate intake and exhaust system also determine how the power is produced.