ATV Repair

Polaris Scrambler 500 Runs But Will Not Idle

Polaris Scrambler 500 Runs But Will Not Idle

The Polaris Scrambler 500 is a popular all-terrain vehicle known for its powerful engine and exceptional performance on rugged terrains. However, like any complex machinery, it is susceptible to mechanical issues. One common problem faced by Polaris Scrambler 500 owners is when the engine runs but will not idle. This perplexing issue refers to a situation where the engine functions when in operation but struggles to maintain a steady, low RPM at idle speed. In this article, we will explore the symptoms of this problem and delve into five potential causes that could lead to this frustrating issue.

Symptoms of the Problem

When a Polaris Scrambler 500 engine runs but will not idle, several symptoms become apparent to the rider. Firstly, the engine may start and run normally while disconnected from a load or out of gear, but as soon as the vehicle comes to a stop or the throttle is released, the engine may stall or struggle to maintain a consistent idle speed. Additionally, the engine may exhibit a slow tick-over or a rough and erratic idle. These symptoms can cause inconvenience during riding and must be addressed promptly to ensure the vehicle’s proper functioning.


Restricted Carburetor Pilot Screw

The carburetor pilot screw plays a vital role in regulating the air-fuel mixture at low engine speeds, such as during idle. If this screw becomes restricted or clogged, it can disrupt the fuel flow, resulting in an unstable idle. Cleaning or adjusting the pilot screw may help restore the engine’s ability to idle properly.

Carburetor Misadjusted

A misadjusted carburetor can cause an incorrect air-fuel ratio, affecting the engine’s ability to idle smoothly. An improper adjustment may lead to either a too lean or too rich mixture, both of which can cause the engine to stall or struggle to maintain an idle speed. Properly calibrating the carburetor can resolve this issue. For a comprehensive and swift solution to troubleshoot and fix the Polaris Scrambler 500 engine issue, download the complete factory repair manual in seconds!

Choke Not Adjusted Properly

The choke enriches the air-fuel mixture during cold starts, and if it is not adjusted properly, it may continue to influence the mixture even when the engine has warmed up. This can lead to a rich mixture, causing poor idle performance. Ensuring the choke is adjusted correctly can alleviate this problem.

Low Compression

Low engine compression can result from various factors, such as worn-out piston rings or cylinder walls. Insufficient compression can lead to reduced power and difficulty in maintaining a stable idle. Addressing the root cause of low compression, such as engine wear, is essential for restoring normal operation.

Crankcase Breather Restricted

The crankcase breather allows gases to escape from the engine, and if it becomes restricted or blocked, it can create excessive pressure in the crankcase, affecting the engine’s performance at idle. Cleaning or replacing the breather can resolve this issue.


In summary, encountering a situation where the Polaris Scrambler 500 engine runs but will not idle can be frustrating for any rider. The symptoms of this problem, such as a rough tick-over or stalling at idle, indicate underlying issues that require immediate attention. By understanding the potential causes, such as a restricted carburetor pilot screw, carburetor misadjustment, improper choke setting, low compression, and a restricted crankcase breather, riders can troubleshoot and rectify the problem effectively. Proper maintenance, timely inspections, and addressing issues promptly will ensure the engine operates smoothly, allowing riders to fully enjoy the Polaris Scrambler 500’s capabilities on any terrain.

Works cited:

The information provided regarding the engine’s inability to idle is based on the factory service manual troubleshooting guide, listing possible causes. Polaris Scrambler Service Manual P/N 9920769