Too Old or Compression Too High

[wolfram]

Newer Stihl MS 260, which I've had for a year and it's been fine. Lately, it's near impossible to pull. No decomp valve and never needed it before.

Measured comp at 150 psi cold and it's tough to pull. Removed plug, turns over free and easy.

Muffler and exhaust port are clean. Pulled the cylinder and found some carbon, but not bad. Cleaned up easily. Piston, cylinder, rings look fine. Case interior is clean and not full of fuel or anything else. Top of piston was not wet.

Reassembled, put in a new plug, and no improvement on pull. And that is without adding any fuel to the tank...

What else should I look at? Any vacuum issues to look for on the intake side? What else?? Thanks for your help.

 

[67L36Driver]

Pull rope getting worn/soft and pinching in the pulley?

 

[BloodOnTheIce]

Take off the rewind, see if the it works properly, try turning over the saw with the flywheel. Between those two things you should be able to find your issue. Where in Western Ny do you live?

 

[Roanoker494]

I would also agree that the starter unit needs inspection and\or replacement. Could be a bad rope, bad pulley or rewind spring.

 

[Motorsen]

Your saw have seasoned!

Your saw have now matured! I think what you now feel is that the saw have been broke in. The piston rings have been broken in and are sealing against the bore much better that new. So the saw feels harder on the pull to overcome the raised compression. The saw now have a higher internal resistance the good way. Have you changed your brand of mix oil lately? If you are running a thicker mix oil you will also experience higher compression an higher internal resistance when cold.
I think and most certainly hope that this is the case for you.
Otherwise you are feeling a binding chainbrake or a beginnig seizure.
Which I ofcourse do not hope or think. Unless you have cut down on cutting expenses an sawed a fortune and now run witout oil in the fuel.

Motorsen

 

[timberwolf]

Work on narrowing it down, pull the rewind and see if it frees up, then pull the clutch side and make sure the clutch and drum is not packed full of guck, then if the motor is still not turning over freely pull the cylinder to see what is going on before it self destructs.

 

[rms61moparman]

Is it flooding by any chance?


Mike

 

[Dan_IN_MN]

Newer Stihl MS 260, which I've had for a year and it's been fine. Lately, it's near impossible to pull. No decomp valve and never needed it before.

Measured comp at 150 psi cold and it's tough to pull. Removed plug, turns over free and easy.

Muffler and exhaust port are clean. Pulled the cylinder and found some carbon, but not bad. Cleaned up easily. Piston, cylinder, rings look fine. Case interior is clean and not full of fuel or anything else. Top of piston was not wet.

Reassembled, put in a new plug, and no improvement on pull. And that is without adding any fuel to the tank...

What else should I look at? Any vacuum issues to look for on the intake side? What else?? Thanks for your help.

I'm sure your dealer wouldn't mind taking a peek at it. He'd know right away if there was a problem.

 

[bcsizemo]

My Echo CS-440 does this, or seems to do something very similar.

If it sits for a while, more than a couple of days, it is fairly hard to pull over. Usually I pull it in short pulls (just 1 turn over) 4-6 times, until the mix gets in the cylinder. Once it does it gets a lot easier. Usually fires on the 2nd pull after it starts to spin free...

Don't know why or how to fix it, just something I live with...

 

[wolfram]

Problem Solved?

I checked the starter unit and all seems fine with engagement, rewind etc.

I then decided to get some exercise. When I reassembled the cylinder on the piston the other night, I used some 2-cycle oil. Maybe too much. After dozens of pulls, things got smoother. I hate it when there is no clear answer....

Maybe the carbon was the initial problem and too heavy and causing an increase in compression. I cleaned off the carbon and used an ample supply of oil in the cylinder during reassembly. After reassembly and a few pulls, it still seemed tight and compression too high.

Now, after many more pulls, it freed up.

Could it be that I used too much oil and it took several pulls for the rings to wipe it and eject it? Who knows...but it seems ok right now.

Thank you very much for the suggestions. Seems to be working, at least for now....

 

[maico490]

Only a very small amount of oil is needed when assembling a saw. Or none at all but that's a whole other story. :hmm3grin2orange:

 

[DSS]

You don't have to put much oil in them before they get hard to pull.

Did it smoke like crazy when it started?

 

[67L36Driver]

I checked the starter unit and all seems fine with engagement, rewind etc.

I then decided to get some exercise. When I reassembled the cylinder on the piston the other night, I used some 2-cycle oil. Maybe too much. After dozens of pulls, things got smoother. I hate it when there is no clear answer....

Maybe the carbon was the initial problem and too heavy and causing an increase in compression. I cleaned off the carbon and used an ample supply of oil in the cylinder during reassembly. After reassembly and a few pulls, it still seemed tight and compression too high.

Now, after many more pulls, it freed up.

Could it be that I used too much oil and it took several pulls for the rings to wipe it and eject it? Who knows...but it seems ok right now.

Thank you very much for the suggestions. Seems to be working, at least for now....

Yes.

When I reassembled my Craftsman/Roper 3.7" I slobbered 2-stroke oil over everything and dumped a couple teaspoons full down the intake. With the new rings and the Roper's undersize starter pulley I couldn't turn it over at all. Had to remove the plug and crank it some twenty or more times to clear it out. It's still near impossible to turn it over more than one at a time.

I need a 'Pull Rope Boy'.

 

[maico490]

I slobbered 2-stroke oil over everything and dumped a couple teaspoons full down the intake.

One drop on the big and small end bearings and just a smear on the rings is plenty. With that much oil you were lucky you didn't break something when you pulled it over. A two stroke has to live it's life on the tiniest amount of oil which is delivered in each fuel charge so doesn't need spoonfuls of oil. The downside to excessive amounts is that it gets behind the rings where it carbonizes and prevents proper sealing. This area behind the rings is crucial to building good compression which is why many two stroke tuners build engines dry.

 

[cbfarmall]

I checked the starter unit and all seems fine with engagement, rewind etc.

I then decided to get some exercise. When I reassembled the cylinder on the piston the other night, I used some 2-cycle oil. Maybe too much. After dozens of pulls, things got smoother. I hate it when there is no clear answer....

Maybe the carbon was the initial problem and too heavy and causing an increase in compression. I cleaned off the carbon and used an ample supply of oil in the cylinder during reassembly. After reassembly and a few pulls, it still seemed tight and compression too high.

Now, after many more pulls, it freed up.

Could it be that I used too much oil and it took several pulls for the rings to wipe it and eject it? Who knows...but it seems ok right now.

Thank you very much for the suggestions. Seems to be working, at least for now....

Not unlike an 076 when the oiler seal lets loose and fills the crankcase. Talk about high compression.

Chris B.