I pulled my MS661 apart for cleaning and inspection last weekend. I found some light scratches on the exhaust side of my piston and decided to go ahead and replace the piston. I put in a hyway pop-up piston with hyway rings. I cleaned the cylinder with a flex-hone and reassembled the saw. I tried to start it up and it coughed a couple times on the 3rd pull. That is all I've got it to do. Any idea's of what might be wrong with it?
MS661 Won't Start
- Thread starter JCCB89
- Start date
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You generally shouldn’t hone chainsaw cylinders because they have a very thin nickasil plating. What’s the compression after rebuilding it? Also, did you identify why the piston was damaged in the first place? If you have a pressure vac tester you can check for an air leak which might be giving you trouble.
Compression is reading about 145. I dont have a vac tester. The saw was running fine when I pulled it apart. I take my 3 most used saws apart and clean them and inspect for any damage or potential problems once a year. This 661 is about 5 years old and I assumed the piston was just starting to scratch from wear. I just wanted to go ahead and replace it before it caused any damage to the cylinder.
How about a pic of the original piston?
I agree with Isaw...piston scoring = pressure and vac test.
Have you tried 1/2 teaspoon of mixed gas down the plug hole...reassemble...attempt to start?
Roy
I agree with Isaw...piston scoring = pressure and vac test.
Have you tried 1/2 teaspoon of mixed gas down the plug hole...reassemble...attempt to start?
Roy
I found the problem today. When putting the carb back on the saw, I had split the fuel line and most of the fuel was going into the carb box instead of into the cylinder. Put a new fuel line on and it started on the second pull. I bucked about 12' of maple into firewood before it got too dark to see, and it ran perfectly.
