Gas trimmer won't start.

[mjncad]

I have a John Deere (Echo?) XT140SB split boom trimmer that decided not to start this year. When I try to start it, I get a jerking motion from the starter cord instead of a smooth pull. I pulled the spark plug out, and the starter cord pulls just fine like it's designed to do. Put the spark plug back in and the jerking motion comes back when trying to start it. I pulled the carb loose and the same jerking motion happens since the plug is still in the head. The piston moves properly so I know it's not a broken connecting rod.

Since it appears to be getting spark and the carb seems to be getting fuel; I'm concluding that there is something wrong in the cylinder/head assembly. A stuck or broken reed valve maybe? According to the JD Parts web site the cylinder/head assembly is replace only.

The trimmer is 9-years old.

 

[greasemonkeyok]

Jerking motion when you pull sounds like too much fluid, oil or fuel, in the cylinder. If you suspect it is worn rings, put a hairdryer on the cylinder fins to heat up the cylinder and try to start it. (Or, set it out in Oklahoma sun for an hour. Cool mountain air won't work.) If it starts, that suggests not enough compression to heat the air/fuel mixture for combustion.

 

[JD755]

Did this problem just start? Has it acted similarly before?

I have a John Deere 25S trimmer (made by Echo) I bought new twenty years ago. It has been worked hard (used it just this morning) but has never failed me. Saying that, there have been times where it was very difficult to start. I would get that same jerking starter rope where I would jerk it off the ground. Changing choke and throttle settings seemed change the jerking effect. Spark was always good. I still have no idea of what was occurring, but combinations of letting it sit a while, changing choke, etc. seemed to eventually let it start. So I have sometimes had a similar effect for many years, but the trimmer has always worked through it. Yours may have a real problem requiring parts, but mine so far has just been an occasionally difficult situation.

 

[mjncad]

Jerking motion when you pull sounds like too much fluid, oil or fuel, in the cylinder. If you suspect it is worn rings, put a hairdryer on the cylinder fins to heat up the cylinder and try to start it. (Or, set it out in Oklahoma sun for an hour. Cool mountain air won't work.) If it starts, that suggests not enough compression to heat the air/fuel mixture for combustion.

The spark plug is dry, so no flooding is occurring. It has been anything but cool here with temps in the 90's.

Did this problem just start? Has it acted similarly before?

I have a John Deere 25S trimmer (made by Echo) I bought new twenty years ago. It has been worked hard (used it just this morning) but has never failed me. Saying that, there have been times where it was very difficult to start. I would get that same jerking starter rope where I would jerk it off the ground. Changing choke and throttle settings seemed change the jerking effect. Spark was always good. I still have no idea of what was occurring, but combinations of letting it sit a while, changing choke, etc. seemed to eventually let it start. So I have sometimes had a similar effect for many years, but the trimmer has always worked through it. Yours may have a real problem requiring parts, but mine so far has just been an occasionally difficult situation.

This problem just started. I have a hunch a reed valve or some such thing went bad in the head. A new cylinder/head unit is $120 and a new piston kit is $80. I'll probably just buy a new one at $300. Changing the choke and throttle settings has no effect on the jerking motion of the starter cord.

 

[Dr Dave]

Take the mufler off and try it. I had one plug up, and caused this. Soaked it in solvent overnight and blew it out. Since then I only use synthetic oil, and have not had a problem.

Dave

 

[JD 420]

I have had a couple Stihl trimmers that the screen in the muffler has been apart completely plugged up. I would take the muffler off and see if the problem goes away.

 

[mjncad]

I pulled the muffler yesterday and the problem remains.

 

[tomd999]

Hiya,

I know it may sound strange but you may want to see if it sheared the flywheel key. I have see it before on several string trimmers, it seems to happen on shut down where it is shut down hot and just as it is coming to a stop, the engine runs in reverse for a half second and you can tell because it tightens against the recoil ratchet with that metalic chunk sound. Most of the time it will be fine but like I said, I have seen it happen.

My buddys Stihl combi did it, he didn't believe me that it was the problem, he took it in to the Stihl dealer, sheared flywheel key, the mechanic said he has only seen it once or twice before. My buddy came back with a six of Sam's and asked if I ever get tired of being right.

Tom