50 Hours: Arctic Cat ZR 858 R-XC

When Arctic Cat released its new 858 C-TEC2* engine with an updated crankcase, air intake system, exhaust valve, and increased displacement and power, we immediately tested one to make sure AMSOIL INTERCEPTOR Synthetic 2-Stroke Oil performs the way it should.

We ran AMSOIL INTERCEPTOR in an Arctic Cat ZR 858 R-XC on our dyno for 50 hours, or the equivalent of 1,000 miles. We measured parameters like jackshaft speeds, throttle position and exhaust gas and coolant temperatures. Then we disassembled the engine and looked at pistons, power valves, cylinder head and cylinders.

Piston Cleanliness

Carbon buildup is expected in a two-stroke engine because oil is consumed as part of the combustion process. Therefore, piston cleanliness is extremely important and the first thing we look for. Piston rings that move freely and have minimal carbon deposits and a clean piston crown indicate that the oil has good detergency and is doing its job.

Exhaust Power Valves

The power valve helps optimize two-stroke power delivery by varying the size of the exhaust port to maximize throttle response and torque at low rpm while delivering high-revving horsepower at the top end. However, the power valve is in the exhaust stream and also subjected to fuel and oil combustion byproducts, so oil detergency is critical to keeping power valves clean and moving freely.

Cylinder Wear

You want to see the crosshatch pattern from the machining process when looking at a cylinder. When an oil is not doing its job, the crosshatch is worn away by the piston rings and disappears. Any deposits on the cylinder heads should be able to be wiped away with a rag, with no hard carbon deposits. We also look for discoloration and other indicators of heat buildup, including on the smaller connecting parts like rods, roller cages and wrist pins.

As seen in the pictures above, AMSOIL INTERCEPTOR performed exceptionally well in all the tests. We saw minimal carbon deposits and the exhaust power valve continued to move freely and work correctly. Cylinder crosshatches were visible with no abnormal deposits, and the engine made good compression and power. There was no sign of heat-related galling, sticking or discoloration in the wrist pins and roller cages. All the critical areas were protected and kept clean, which is exactly what you want out of your two-stroke oil.

Watch the video below for a deeper dive into the test results and grab some AMSOIL INTERCEPTOR to maximize performance in your two-stroke sled.