044 Lean Seize

[rxe]

A friend asked me to look at his 044. The symptoms were failure to start (or even cough) from cold. Compression felt weak, and this was confirmed with a test: 110 psi. Looking at the piston though the exhaust port, it didn't seem that bad, but given the pressure readings, the cylinder had to come off. Sparks and fuel are fine.

So off comes the cylinder, and what do we see:

View attachment 174139

Loads of scoring, the piston's rings are smashed into the piston and the bore is toast. Ho hum.

Now to the question: I would expect a lean seize to take out the section of the piston directly facing the exhaust port. Instead this seems have taken out the sections either side of the port. Any significance to this? Or is this normal for a "modern saw" (I'm more used to 070s and 090s)?

If it helps, the full story is as follows:

- The fuel tank was filled with bar oil in the morning.
- The operator realised immediately, tipped the bar oil out, flushed the tank with mix, threw that out, then refilled with mix.
- The saw worked fine for about a tank.
- It wouldn't start again after refueling.

I'm guessing that the saw was close to the limit anyway, and a bit of remaining bar oil clogged the filter/carb just enough to push it over the edge. There were no reports of high/erratic idles that would suggest an air leak, but yes, I will check!

 

[Beaver eager]

What does the carb look like? Like you said it may be the bar oil got in the carb and messed up the whole thing. Gas should have dissolved it but I'm not sure if it would also dissolve the tackifiers in the bar oil. I would suspect that would lean things out on you. Crank seals would be guess #2.

 

[RiverRat2]

only the exhaust side of the piston toasted????

 

[mtngun]

- The fuel tank was filled with bar oil in the morning.
- The operator realised immediately, tipped the bar oil out, flushed the tank with mix, threw that out, then refilled with mix.
- The saw worked fine for about a tank.
- It wouldn't start again after refueling.

Weird. I dunno what to tell you, but I hope you find a smoking gun.

Hard to believe residual bar oil would hurt anything. It should dissolve in the gas, 'specially since he rinsed the tank with mix -- unless he actually ran the saw after filling with bar oil, in which case the carb could be a mess.

 

[rxe]

Intake side of the cylinder is fine, looks like it has done a fair mileage, but fine.

View attachment 174143

The carb is clean, filters all clear. The only thing worth noting is that the H screw was half a turn out. I would expect it to be at least a turn - I reckon this has been on the edge for a while.

 

[RiverRat2]

Intake side of the cylinder is fine, looks like it has done a fair mileage, but fine.

View attachment 174143

The carb is clean, filters all clear. The only thing worth noting is that the H screw was half a turn out. I would expect it to be at least a turn - I reckon this has been on the edge for a while.

Uhhh yeah 1/2 turn on the H is lean,,, I would flow check the carb if it flows mix well with both covers off, filling up the inlet cavity it prolly was the lean setting on H,,,, Pressure and vac test to be sure and if all good make your repairs, rebasline the carb,,, and youll be good to go!!!

 

[pioneerguy600]

Been run lean for quite some time, the piston heated and swelled at the skirt edges causing scoring at the highest pressure points.
Pioneerguy600

 

[RiverRat2]

Yep them dumb rednecks with a little screwdriver will do it everytime!!!

 

[homelitejim]

I have run into the bar oil in the gas tank with a Stihl 017. I rinsed out the tank and refilled with mix, must have been some in the line because when it fired up the smoke was impressive. The owner must have put bar oil in from the get go because the P&C looked brand new. I would not think bar oil would cause your lean condition but a rich condition.