Stihl 026 super high compression after sitting

[BobbyC]

I have a Stihl 026 (1989) which gets used quite infrequently. After sitting for a few months the compression is unbelievably high. So much so that I can barely get one revolution out of it pulling as hard as I can. With sparkplug out it spins as easy as you'd imagine. Put the plug back in and it it is still extremely hard. So I gave it a shot of starting fluid. On the first pull it was still very hard and did not fire at all. BUT it seemed to free up and after than it pulled normally and started after a few pulls.

I'm assuming the difficulty in cranking it is compression. This is always the way it is - after it sits for an extended time it is a bear to turn over. After it starts it then turns over very easily until I put it away for an extended period.

Ideas? Thanks!

Bob

 

[trooney]

The piston was probably dry. Putting starting fluid in there was not lubricating it. When it got mix in there it started loosenibg up due to the mix lubricating the cylinder. Next time if it sits, shoot a little mix down the spark plug hole.

 

[trooney]

I should say the cylinder was dry also

 

[legdelimber]

Just me spitballing a random thought here, so take it as such.

Have you looked at the spark plug after pulling the recoil a few times after the saw has been siting? Oily or wet?
Any extra smoke or "blubbering" when it fires for the first time after sitting?
I'm wondering if it's building pressure in the fuel tank, when sitting for extended times.
Possibly pushing fuel into the engine.
Given enough time, fuel could evaporate and leave the mix oil behind.
Might be enough to make engine hard to pull over?

Maybe dump the fuel before next time the saw gets parked and leave the fuel cap a little loose?
See if it makes any difference. Cheap to try at least.

Another thing would be remove spark plug and turn saw upside down and thne pull the rope a few times (fast pulls) and see if anything blows or dribbles from plug hole?
Just like clearing a badly flooded saw.

 

[drf256]

Make sure your carb is holding pressure. Probably floods on sitting from tank pressure exceeding needle/seat pressure. Mix gets up to the cylinder With first few pulls.

Same thing happens with saws when freshly built and too much assembly oil used. It doesn’t take much oil in the cylinder to make a saw hard to pull over, and then if it fires before TDC without enough speed, you get bitten.

As said above, id check the plug and turn it upside down and pull it over without the plug. See if mix/oil drips out the plug hole.

 

[BobbyC]

All good tips - thank you very much! The plug looked pretty dry when I pulled it (if I recall correctly). It rev'd pretty high when it did start (no excess smoke) but with some of the covers off I lost track of where the STOP/RUN/WARM/COLD lever was. This is an impressive forum!

 

[trooney]

Like I said, it orobably took a little while for the impulse to pull the mix to your cylinder. It didnt help it that you were pulling half strokes. If you emptied out the fuel tank before you let it sit, spray some mix down the hole to make it easier to pull fuel through the hose to the carb.

 

[hacskaroly]

So I gave it a shot of starting fluid.

If you need to put something in the cylinder other than mix fuel to try to loosen it up, I have used WD-40. It will lubricate and burn off, starting fluid just burns (much like straight gas - no lubrication).

 

[Arcticmiller]

Along similar lines, I had a snowmobile I was working on that had sat for 10 years or more. It would barely pull over. I pulled the head to see if it was a bad bore. It was fogging oil, someone had pickled it for storage and the oil basically dried out and gummed up the bore/piston interface. It was sticky. A little wipe with some gas on a rag and it fired right up. It was the best stored machine I’ve ever worked on. They emptied the gas tank, cab bowl, etc and fogged absolutely everything. Someone cared about it.

I wonder if it’s mix gas deposits and mix oil getting deposited in the bore and being sticky.

 

[drf256]

The saw rotates over fine if plug is out. A dry cylinder would still be stiff.

 

[Arcticmiller]

It would be interesting to see the compression numbers then….

 

[drf256]

Along similar lines, I had a snowmobile I was working on that had sat for 10 years or more. It would barely pull over. I pulled the head to see if it was a bad bore. It was fogging oil, someone had pickled it for storage and the oil basically dried out and gummed up the bore/piston interface. It was sticky. A little wipe with some gas on a rag and it fired right up. It was the best stored machine I’ve ever worked on. They emptied the gas tank, cab bowl, etc and fogged absolutely everything. Someone cared about it.

I wonder if it’s mix gas deposits and mix oil getting deposited in the bore and being sticky.

I wonder. This makes sense too. Could be your mix.