What's going on with this trimmer engine?


LawnSite Fanatic
I tried to pull start a 5 years or more old Redmax trimmer today and it kicked over once. Then when I tried pulling the cord it would not budge. So I looked at youtube and on here. And saw ed2hess said to take the pull cord off and try turning it by hand, remove the spark plug and put a little oil in there, turn it by hand a few times, then run it lightly with extra 2 cycle oil and seafoam in mix. What type of oil? I put about a half of teaspoon of 2 cycle in the spark plug hole?

I did that, without adding the Seafoam, since I have Star Tron already in the mix, and it runs. But I wanted to know what is causing this technically. I imagine old age has a lot to do with it.

What I noticed after removing the plug is, it is pretty dark/black in there. When I turned it by hand, it would start to make a scratching noise, when the ( piston? ) would get closer to area where the spark plug was. A couple of times, I could not get it to complete its action, and had to turn it in reverse.

I have some Seafoam, but did not put it in the gas. The gas mix I've been using for 10+ years was the red max bottles with 89 octane, and I have been putting Star Tron in the mix for the last two years. The gas is E10. I don't know if I should put the Seafoam in the mix that has Star Tron in it.

But again I was curious to what is causing the scratching? Dirt? Ethanol? And technically what is occurring?


LawnSite Fanatic
Memphis TN
Take the head apart. Pretty easy on these and get a look at the rings and the cylinder wall. If you've got an hour or two to spare. Probably preaching to the proverbial choir but take the muffler off and look at the exhaust port. If no build up look in it and you can see some of the cylinder wall and inspect without taking it completely apart.

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