How to Troubleshoot Stihl Chainsaw Model MS 170

When a Stihl model MS 170 chainsaw breaks down and stops working properly, the issue comes most often from one of three areas in the chainsaw engine. To troubleshoot and locate the problem, isolate the issue in an area of engine operation, such as spark, air or gas. When you locate the missing element --- whether of fuel, spark or air --- you can often find the source of the increase or decrease of that element in the carburetor or engine.

Combination bar tool
Replacement spark plug
Work gloves
Approved fuel container
Metal hook
Fuel filter
Brush
Rag
Replacement air filter (if necessary)

Instructions

- 1
  Unhook the rubber boot on top of the spark plug, which is located on top of the MS 170's engine. Loosen and remove the spark plug with the spark plug socket side of the combination bar tool. Take out the spark plug and insert the replacement plug, metal tip out, into the rubber boot.
- 2
  Wear leather gloves, and put the chainsaw on the ground. Hold the lead wire just below the boot so the spark plug's tip sits approximately ½ inch from a grounded metal point on the engine block.
- 3
  Put your foot in the rear handle and pull on the starter cord. Take the Stihl MS 170 to a mechanic to service the ignition system if the chainsaw doesn't produce a clean, blue spark during the ignition test.
- 4
  Unscrew the fuel cap and drain the tank into an approved fuel container. Reach in and pull out the fuel filter and fuel line, using the metal hook. Pull off the fuel filter. Check the fuel hose, and replace the fuel line if it looks cracked, yellow or brittle in any way. Insert the nozzle of the new fuel filter into the fuel hose.
- 5
  Brush out the tank, using a rag wrapped around the brush's head. Check the tank for any damage. Unscrew the air filter cover and take the air filter off the chainsaw. Brush off the area around the filter's mount, the choke plate, the air filter and the air filter cover. Replace the air filter if it's too dirty to be brushed clean.
- 6
  Try restarting the Stihl MS 170. If the chainsaw runs but runs poorly or idles roughly, take it to a mechanic to adjust the carburetor.

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