Stihl 4 MIX Troubleshooting and Repair Guide

Stihl 4 MIX Troubleshooting

Stihl 4 MIX Troubleshooting

Before any Stihl 4 MIX Troubleshooting repair work is performed on a machine, a thorough evaluation should be made to determine what parts are actually in need of replacement or maintenance. The service manuals for STIHL 4-MIX engines outline testing procedures as well as special tools that are needed to repair the equipment. The STIHL troubleshooting guide is an ideal check list to use when performing repairs and will assist the repair process in performing a step by step analysis of the machine.

Repair Procedures of Stihl 4-MIX Engine Quick Check List

  1. The fastest way to find any major fault is to quickly check for compression, ignition, spark,and fuel delivery.Use a spark tester to verify that spark is present
  2. If the engine has no spark, the spark plug, the ignition module or stop switch system is at fault.
  3. If the fuel system is completely restricted, the engine may not fire at all when trying to start it. Squirt some choke spray in the carburetor and try to start the engine.
  4. Does the engine have any compression?
  5. Is fuel getting to the combustion chamber?
  6. Does the engine have a spark?

On Stihl 4 MIX engines, if compression feels low, or if the spark is okay and fuel is getting to the engine, then do a leak down test.
This only takes a few minutes. If the leak down is below 10%, then the combustion chamber is okay and the running problems are due to something else.
If the leak down is greater than 10%, the problem needs to be repaired, as well as making sure that there are no other faults present.

Stihl 4 MIX Troubleshooting Help

The STIHL 4-MIX Engine Check Worksheet is a simple guide to verify any faults found in a logical and efficient manner.
Worksheets are available for both 2-cycle and4-MIX® engines.
An accurate repair cost estimate can then be prepared.
Throttle Operation
Verify that the throttle works smoothly, and that the throttle interlock is working correctly.
The throttle cable should be adjusted so that the throttle is opening all the way to the stop on the carburetor without causing excessive tension on the cable.
Be sure that the throttle returns to idle easily and smoothly.
On a shaft mounted 4-MIX product, inspect the cable for fraying where it slides over the plastic cam on the carburetor flange.

Stihl 4180 Engine Series – Throttle Adjustment Procedure

To adjust the throttle correctly on a shaft mounted product, set the screw on the adjuster cam that is located on the carburetor flange so the same amount of threads show on either side of the cam.
Next, using a small screwdriver, push down on the tab located in the top of the throttle assembly and slide the tab towards the engine.
Now squeeze the throttle to the wide open position. The tab will slide forward and automatically adjust the throttle cable. Release the throttle trigger and verify the attached throttle lever comes back fully to idle. The throttle cable should always be checked for proper adjustment when a new machine is set up for delivery and anytime a machine is in for service.

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Stihl 4 MIX Troubleshooting Diagrams

The Stihl 4-Mix engine has 2 valves and two pushrods. The exhaust valve has a brass sleeve the pushrod rides on. If you run the 4-mix in heavy grass or for extended periods of time in high ambient temps the brass sleeve will fail under high heat of the 4-mix engine; causing the push rod to drop onto the piston head seizing the engine.