Stage Tuning the Polaris AXYS 800 with Starting Line Products

In just two short years, the new Polaris 800 H.O. 2-stroke twin (only found in the Polaris AXYS models) has quickly gained a reputation as being an extremely potent powerpack with wicked-fast throttle response, making it really fun to ride. The crankshaft alone is 2.5 lbs. lighter for quicker acceleration and less inertia. It is 3.5 pounds lighter than the previous 800 Liberty twin and has three-stage electronic power valves with an electronic oil pump. It not only produces excellent power with greater durability, it is also far more responsive with improved fuel economy and reduced noise levels.

The Polaris 800 AXYS engine is entering its third year of production and has proven to be very durable and is truly living up to its H.O. (high output) designation. We have put thousands of miles on these engines without issue. For the performance minded (which would include all of us), this is a great engine to modify. It responds well to modifications and delivers performance increases only dreamed of in years past, along with great reliability. Here are the performance boosting Stage Kits now available from Starting Line Products (SLP) with some extra insight behind each one.

Each of these performance stages will work with any of the 2015-2017 Polaris AXYS 800 models, including RUSH, Switchback, Assault & RMK. The pricing shown here for each of the kits depends on the exact model and operating elevation. Contact an SLP technical expert for exact details of your application.

Stage 1:
SLP Lightweight Silencer – $446 +2 horsepower, -11.5 pounds
The purpose of Stage 1 is primarily to shed weight and give the sled a more robust sound (the silencer is close to stock sound levels with a slightly deeper, throatier sound). As an added bonus, an additional 2 horsepower peak is also delivered. This stage is a popular starting point with many riders as a pipe can be added at a later date that is fully compatible with this silencer. In the field, it shows 2 lengths faster in a 3/10s mile drag race and 3 lengths faster up to 95 mph. On the Pro RMK 155 model, this brings the dry weight to under 400 pounds (395.5 pounds based on Polaris’ published dry weight).

Stage 1.5:
SLP Lightweight Silencer & Power Dome Billet Heads – $881 to $906
+6.2 horsepower, -11.5 pounds
SLP had a lot of call for heads to be used with the stock pipe, so during product development, SLP decided to test this direction. What they found was the heads used in conjunction with the stock pipe showed great throttle response with better acceleration and top speed. Its throttle response is slightly better than the Stage 2 kit, but top end speed and power is not quite as good. Those operating more at partial throttle – trail riders running tight, twisty trails or mountain riders who spend the majority of their time in the trees – really like this kit. The throttle response is great and the sled becomes more agile from the weight savings of the silencer. Performance wise in the field, this kit shows an additional 4 lengths faster in a 3/10s mile drag race.

Stage 2:
SLP Single Pipe Set – $866 to $891 +9 horsepower, -14.5 pounds
The Stage 2 kit is the core of performance value on the AXYS 800. Most riders either start here or work up to this stage from Stage 1 as their budget allows. It consists of an SLP single pipe kit and clutching. The pipe kit was designed to work in conjunction with the stock ECU. A resistor is placed in-line with the EGT sensor that adds approximately 4% more fuel at engine rpms above 7700. This is the only area where additional fuel is needed, so it makes a very simple, cost effective means of delivering it. And oh my, it really delivers some great performance gains. In the field it shows an additional 6.5 lengths faster in a 3/10s mile drag race with an added 5 mph top speed. The top speed comes from the higher running rpm (8300-8400 with a pipe verses 8250 stock). AXYS owners who have this pipe comment that it provides dramatically different performance than stock and transforms it into a whole new sled. They also question the 9 horse gain as in the field it feels like much more than that, the performance is really that good. It snaps right to attention and pulls much harder than the stock pipe from engagement on up.

The clutching that is recommended is one of the keys to performance. Specifically the SLP MTX weight with its heavy heel design pinches the belt harder in the low to mid speed ranges to load the engine and bring the internal pipe temperature up quickly. This provides better acceleration and more consistent power each time you touch the throttle with the SLP pipe installed.

Other items that are highly recommended, but not necessarily included in the Stage 2 kit are the SLP torque arm ($110) and the SLP High Flow intake ($65). The torque arm is mounted between the electric start mounting location and the bulkhead (and yes, SLP has one for electric start models). It uses a special rubber dampened heim joint to eliminate vibration transferred into the bulkhead, yet keeps the engine in place when under a heavy load or hard acceleration. SLP has found a gain of 1.5 lengths in acceleration simply by installing the torque arm – seriously.

The SLP High Flow intake is recommended when running in deep snow. It adds 57% more intake surface area and really helps with air flow when snow starts blocking some of the stock intake vents. This is primarily used for consistency purposes on this stage, especially in light powder snow conditions that typically restrict stock intakes.

Stage 3:
SLP Single Pipe Set & Power Dome Billet Heads – $1301 to $1826
+12.4 horsepower, -14.5 pounds
The performance that the Stage 3 gives is pretty awesome. It combines the SLP single pipe kit with an SLP Power Dome billet head set and clutching (at elevations below 5000’, a Bully Dog GT is used to re-map the ECU for fueling purposes). These products are bolt-on with no internal engine modifications. The performance that is realized from this kit for the dollar spent is quite incredible.

The SLP Power Dome billet head set combined with the pipe is the key to its excellent throttle response and feel. This is due to the unique dome design (which in and of itself adds performance) and compression ratio of the Power Dome heads. SLP offers three different head compression ratios depending on the lowest elevation that the sled will be used at. This allows you to maximize the compression for pump fuel at that elevation (essentially, you are able to utilize higher compression ratios at the higher elevations due to the reduced air pressure at elevation).

This Stage 3 kit is an extremely popular combination for mountain riders as it snaps to attention at the touch of the throttle and delivers a peak horsepower level that is considerably higher than stock. As with the Stage 2 kit, SLP recommends the use of the SLP High Flow intake kit in deep snow conditions and the SLP engine torque arm. These two parts are not included in the kit, but are very beneficial.

Stage 4:
Performance Edition Kit – Typical total $2,605
+15.7 horsepower, -14.5 pounds
New for this season from SLP, the Stage 4 kit maximizes the horsepower output available on pump fuel for the AXYS 800. It combines internal cylinder porting, exhaust valve modifications and y-pipe match porting with the SLP single pipe kit, SLP High Flow intake kit, SLP clutch kit SLP engine torque arm and Bully Dog GT.

The cylinder porting increases the airflow efficiency inside the cylinder and the port timing is modified as well to specifically provide more upper midrange and top end power. Uniquely designed head domes (specific to the Stage 4 kit) compliment the cylinder porting and provide throttle response similar to that of our Stage 3 kit while allowing the additional power on top. These domes utilize a special ceramic coating on the combustion side. The inside of the exhaust y-manifold is also ceramic coated to bring the internal temperature of the exhaust to operating temperature quickly. These additions provide consistent power each and every time you whack the throttle.

The SLP engine torque arm is considered to be a mandatory component for this combination as it keeps the clutches in alignment during heavy load or acceleration.

The Bully Dog GT module is used to modify the stock ECU programming in order to provide the proper fuel and ignition for this combination. Once modified, the Bully Dog GT can be removed or if you’d like to keep it on as a monitor, it can be programmed to watch any of the stock sensor inputs to the ECU.

In the field, the actual performance is pretty astonishing for a naturally aspirated engine running on pump fuel. The power peak is very broad which makes this combination very resistant to rpm loss as elevation or conditions change. Even though it is in a very high state of tune, it is also the most consistent combination of all the stages. AXYS owners running this combination will find themselves unable to wipe the smile off of their faces from how responsive and powerful this actually is. Having this much power in a sub-400 pound sled delivers an incredible power to weight ratio, making it super responsive and extremely fun to ride. You will be able to quickly pop up out of the snow and pull hard through the entire powerband.

Currently this kit is only available for elevations of 4000 feet and higher. SLP plans to release it for lower elevations once validation testing is completed – contact SLP for the latest on availability.

Conclusion
The Polaris 800 AXYS is a wonderful sled and makes a great platform for modifications. Each of these stages were designed and tested using 91 octane pump fuel. And, each provides a solid gain with reliability and consistency in mind. They are essentially a series of steps of performance that can be done as one’s budget allows while utilizing most or all of the parts from the previous stage. Call Starting Line Products with any questions you may have (208-529-0244) and speak with one of their knowledgeable technicians, who are also avid snowmobilers just like you.