MS250 start compression relief stopped working

[Bubster]

Yes you have to have a camshaft for an auto decomp to work. My only problems with an 025/250 not cranking over easy has always been the fuel metering valve letting too much fuel in. Many people complain about the 250 being hard to crank though.

As it turns out Partner did make a saw with an auto decomp.

 

[Chevboy0167]

Husyk 357 XP...

https://www.partstree.com/models/357-xp-epa-husqvarna-chainsaw-2007-03/piston-cylinder-10/

 

[rocketnorton]

As it turns out Partner did make a saw with an auto decomp.

+ pioneer had a few

 

[spuldup]

Not sure if you've sold the saw yet but I found a solution for this on my MS 250. After about the same # of hours as you it became hard to start. It was never an easy one from the get-go but I'd only have to drop-start it 3 times and she'd bark.

I found it was carbon buildup on the squish band. I cleaned the cylinder and started running it differently. Keep the rpms up even when limbing, and get it in some big wood whenever you can. Especially if using the Stihl oil. These like to eat. So, if you still have it check the squish. If you can't pull it through the solder it is too low and needs cleaned.

More on this saw: if running an 18" bar, use winter blend bar oil year round. That was recommended by the dealer and has dramatically helped my chain wear. Lastly is to open up that darn muffler (and often times the gasket). Very restrictive. I drilled mine straight through and made a custom deflector that secures with existing muffler bolt. If you cut in dry woods obviously get a screen in there.

 

[tommyus4]

Mine is not a tough to start issue. It's a rip your hand off problem. It's a new problem, I've had the saw for 13 or so years. A stronger person would just break the cord or rip their hand. Mine has always just started right up. Then it got a bit jerky. Now it is impossible to get it past 4 to 6 inches without ripping back. It's not the rope.
I take the spark plug out (like I read here) and it pulls smoothly. Put it back in, just to cover the hole, not even screwed in and same problem. I would think pulling the spark plug (air vent) would be a clue.
It wasn't running properly starting about 2 weeks ago. It would idle when turned to off and pulling the trigger then turned it off. But that's real recent, like the last few days. I was just testing some sharpened chains. It also starts up from the choke if you push it up. Again, real recent. Same time as it started jerking my hand a bit to pull start. Not a big believer in coincidences. Kind of mad at myself for not just adjusting it 2 weeks ago. I used it for about 3 hours with it running not as smooth as it should. On and off maybe 12 times. If that ruined it, stupid me. Live and learn. Still sucks.

 

[spuldup]

Have you checked for carbon buildout in the upper cylinder? After 13 years a saw needs a good teardown/inspection.

 

[cookies]

Try running decarbonizing engine cleaner through the saw with it running and warmed up. It takes a very small steady stream to lightly load it up with cleaner then clear it out by revving the engine some. Once most of it is cleared out reinstall the air filter then make a few cuts and repeat the process. You can also hold the saw on its side with the plug removed and using a syringe inject about 1/2 of a ounce of marvels mystery oil, reinstall the plug and store the saw upside down for a day or two. Drain the oil, wash the plug and then run it hard. The idea is to fill the top of the cylinder with the MMO with the piston all the way up so it stays coated in the MMO softening the carbon so it comes loose and blows out in use. See if this helps before throwing parts at it.

 

[tommyus4]

Spuldup: This happened two days ago and all I did was take off the cover to check the rope. Read a few things and took off the spark plug to see if it pulled smoothly and it did.
I don't know how to check for the carbon buildup. I will read and figure it out. I've fixed our pellet stove a zillion times, my splitter and replaced carbs on things. But I'm not exactly a tinkerer. It's obviously not cost effective to get this fixed unless I do it myself. I will try. Thank you.

Cookies: I can't get it to run. Ran the day before. There was a hint of a problem. On a few pulls I'd get that serious resistance but then I could get it to a place where it didn't happen and I could get it to start. Now it's impossible to pull start it. Killed my hand trying. It's not smooth and way too much resistance to get the flywheel to spin. But it's smooth as silk with the spark plug out. I should have done what you said at the first hint of the jerking issue.
Thank you BOTH for responding.

 

[cookies]

Spuldup: This happened two days ago and all I did was take off the cover to check the rope. Read a few things and took off the spark plug to see if it pulled smoothly and it did.
I don't know how to check for the carbon buildup. I will read and figure it out. I've fixed our pellet stove a zillion times, my splitter and replaced carbs on things. But I'm not exactly a tinkerer. It's obviously not cost effective to get this fixed unless I do it myself. I will try. Thank you.

Cookies: I can't get it to run. Ran the day before. There was a hint of a problem. On a few pulls I'd get that serious resistance but then I could get it to a place where it didn't happen and I could get it to start. Now it's impossible to pull start it. Killed my hand trying. It's not smooth and way too much resistance to get the flywheel to spin. But it's smooth as silk with the spark plug out. I should have done what you said at the first hint of the jerking issue.
Thank you BOTH for responding.

take the plug out and turn it so the muffler faces at the ground, pull he handle and look for excess fuel out of the muffler and or plug hole. Sounds like the carb is bleeding fuel into the cylinder.

 

[tommyus4]

I'm going to do that right now. DON'T MOVE. lol...thanks.
I also should have said that I bent out the baffles on the muffler 10 years ago. I don't remember if I messed with the screen. Tuned it with a tach. It cut WAY better but I kind of figured this might shorten it's life. The 'gas mileage' went way down. The chain oil to gas is went from 1 to 1, to about 1/4 of the oil left when I run out of gas.
I should have been doing preventive maintenance but I didn't. Quite possible carbon buildup and scored piston? Not that much to replace. Just the learning curve. I refuse to buy anything new until every option is tried, which means at least I learn something. Like keeping my 24 y/o Sears riding mower going. Been a battle and a half but it still works.

 

[tommyus4]

I pulled it 20 or so times and no leaking. I put the plug back in and it had less resistance. Then the resistance came back after 1 and a 1/2 pulls. But I could get it all the way, just very jerky.
I then pulled it about 100 times and no leaking but I could then pull it 3 times, very jerky but then back to super resistance. So pulling it with an open hole gets rid of compression?
Two other things. It smelled super gassy (open hole, normal?) and the spark plug looks old, like I'd replace it had it not been new 6 months ago.

 

[cookies]

I think the carb needs a rebuild or replacement, sounds like too much fuel is being drawn in during the choke. Try this..pull the plug and clear the fuel. No choke try to start it.

 

[2StrokeFondler]

The chain oil to gas is went from 1 to 1, to about 1/4 of the oil left when I run out of gas.

That's not a bad thing...

Have you tried emptying the tank completely before you pull it? Maybe some pulls without spark plug first. That way you can check if the fuel/carb does have anything to do with your issue. Carb can't flood the saw if it hasn't no fuel left, right?

 

[tommyus4]

I actually did that. Cleaned off the plug, connected it and tried. I couldn't get a pull through. Came close to a full pull.
------------------------------------------
Okay I wrote the above and forgot to send. What I failed to do was screw the pull cover in tight so I did it again and it started. I'm stunned. Just a quick pull. Didn't even go more than 1/2. Like quickest pull ever. I'm guessing you knew that. I sure as hell didn't think that was possible.
Did me pulling it upside down 150 times do something to make the carb work? And or get rid of compression? Or just the cleaning off the spark plug? All of the above? THANK YOU, btw.
I would really like to know what just happened. I'm thrilled, seriously thrilled, just mechanically semi clueless.
No air filter on. No bar and chain (obviously) but I did have to choke it out to shut it off.
Thank you again.

 

[cookies]

You cleared the excess fuel out of the engine, rebuild the carb or replace it Is where I wuld go next...Probably needs decarboning as well.

 

[tommyus4]

That's not a bad thing...

I missed your post, sorry: Since it jumped from being a firewood cutter to something that I could use to cut fallen trees, I agree. I got my money's worth. Still want it to work, though. I also have a 362 that is a year younger, that I use 3X as much.
I did what Cookies said. I then let it sit for 2 hours. I tried starting it and couldn't pull it. I took the plug off, super dirty again, pulled the cord 50 times with the plug out. Put the plug in and it started right up. This time I ran it for a while. So at least I know I can get it started. But I have to flood it to shut it off. I'll run the decarbon stuff through it. Take the muffler off and clean behind it. Retune it. If the pull thing is still an issue then I will replace the carb.
Anyway, nice to have people help. Really nice, actually.

 

[cookies]

I missed your post, sorry: Since it jumped from being a firewood cutter to something that I could use to cut fallen trees, I agree. I got my money's worth. Still want it to work, though. I also have a 362 that is a year younger, that I use 3X as much.
I did what Cookies said. I then let it sit for 2 hours. I tried starting it and couldn't pull it. I took the plug off, super dirty again, pulled the cord 50 times with the plug out. Put the plug in and it started right up. This time I ran it for a while. So at least I know I can get it started. But I have to flood it to shut it off. I'll run the decarbon stuff through it. Take the muffler off and clean behind it. Retune it. If the pull thing is still an issue then I will replace the carb.
Anyway, nice to have people help. Really nice, actually.

You need to look at and repair the coil ground used to shut the saw down, do not continue to use the choke to shut it off. This could be part of your issue, essentially you are flooding the engine with fuel until it shuts off. Fix the coil/wire/selector shaft problem and see if that helps

 

[tommyus4]

The detached wire with clip end might be the reason? I would think it should be attached to something. The smaller black thing flips over and a metal clip goes into the middle when turned to off. Kill switch (Coil ground?) . It seems this wire needs to be attached to that but I don't see where it slides onto anything that's obvious.

 

[tommyus4]

I did the obvious. Start it up and touch that clip to the metal that flips over when it's turned off and it shuts down. That clip slides into that plastic thing perfectly. I would have thought it slid into something metal like a clip is designed for. Nope. Fits in perfect, started again and now it turns off. That is really lazy of them. Maybe a metal piece is missing but it fits perfect and works.
THANK YOU. I never would have figured it out without being pointed in the right direction.
PS: It also started it 3 times in a row without messing around. Again, thanks.

 

[a. palmer jr.]

One solution might be to put it on the tailgate of your truck and take a nice, fast drive down a country road. BTW, I have two of them and they both do the same thing, difficult to pull.