My saw is broke....

[xyz123]

I guess I can start there....???? Any input anyone??

What does the piston and rings look like right now with muffler off? Not last time it was off.
What does cylinder look like through spark plug hole with plug out? What does the intake side of piston look like with carb off looking through intake?

or you just need to disassemble and check.

Min (worst case) clean up piston if need be, clean up cyl if any aluminum transferred, re-ring , base gasket.

Find out WHY it did this? air leak? carb tune wrong (to lean) ?

Last like new 5000 I bought not running, that I had to fix was killed due to a dull chain being run in the cut for long periods and being pushed would be my guess. The ring had turned blue in the front and stuck in groove with a hair of scoring visible. Cleaned up and running.

 

[Nitro-Fish]

I would take it back to the dealer that fixed it for you and make them do right by you; make them show you how well it runs (and make sure you let it get hot) before you accept it. The compression check can vary depending on the guage you use; where is the schrader valve in the guage? A saw with 120 psi should start & run fine, just be down a bit on power, I've seen some run with as little as 90.

I would check your fuel lines (& impulse lines if applicable) before going too crazy, the 10% E fuel really takes its toll on the the fuel lines, especially if you leave fuel in them for long periods of time. Another thing I have seen is the diaphram getting stiff & not allowing the carb to pump properly from people draining all of the fuel out (running completely out of fuel) before putting the saws away for long periods of storage. I have found the best way to keep things working is to drag everything out every couple of months & run them a bit just to keep them exercised, of course this can become a bit like work when you have too many.

Make sure your air filter is clean, make sure you use good 2 cycle mix (Stihl, Husqvarna or the like, not off brands), & make sure your ratio is mixed right. Don't be afraid to dump fuel out if it has been sitting in the saw for more than 4-6 weeks, better safe than sorry, P&C's get expensive quick.

 

[xyz123]

Mentioning fuel line.

Fixed another MS250 that wouldnt stay running. Had good PSI and visible fuel line cracks.
Filled tank and watched fuel seep making line look wet. Put in new line ran great again.

No dealers open to get stihl oem molded fuel line and mail order would have took to long. Guy needed saw that evening to cut. So I figured out a way to not have to use that expensive stihl molded fuel line. Works like a charm and still going. :thumbsup:

 

[Gobblin Tom]

I would take it back to the dealer that fixed it for you and make them do right by you; make them show you how well it runs (and make sure you let it get hot) before you accept it. The compression check can vary depending on the guage you use; where is the schrader valve in the guage? A saw with 120 psi should start & run fine, just be down a bit on power, I've seen some run with as little as 90.

I would check your fuel lines (& impulse lines if applicable) before going too crazy, the 10% E fuel really takes its toll on the the fuel lines, especially if you leave fuel in them for long periods of time. Another thing I have seen is the diaphram getting stiff & not allowing the carb to pump properly from people draining all of the fuel out (running completely out of fuel) before putting the saws away for long periods of storage. I have found the best way to keep things working is to drag everything out every couple of months & run them a bit just to keep them exercised, of course this can become a bit like work when you have too many.

Make sure your air filter is clean, make sure you use good 2 cycle mix (Stihl, Husqvarna or the like, not off brands), & make sure your ratio is mixed right. Don't be afraid to dump fuel out if it has been sitting in the saw for more than 4-6 weeks, better safe than sorry, P&C's get expensive quick.

I did order a plug to replace the decompression valve. I also went and bought a compression guage of my own. I figured I would start with the cheap small stuff and go from there... A guy I work with said it might be another piece of dirt in the carb?? I'm just going to try the plug 1st and see what happens. I don't know anything about the fuel lines and impulse lines??

 

[Gobblin Tom]

Mentioning fuel line.

Fixed another MS250 that wouldnt stay running. Had good PSI and visible fuel line cracks.
Filled tank and watched fuel seep making line look wet. Put in new line ran great again.

No dealers open to get stihl oem molded fuel line and mail order would have took to long. Guy needed saw that evening to cut. So I figured out a way to not have to use that expensive stihl molded fuel line. Works like a charm and still going. :thumbsup:

Yeah ok I'm jealous!!! I would be happy if mine ran!!!!

 

[RobertN]

The fuel lines in small equipment do not hold up well to the oxygenated gas. They turn to mush, and will collapse, cutting off gas.

The impulse line is how you pump the gas. The impulse line connects to the crankcase. As your engine cranks over, there will be a rise, and then fall in the crankcase pressure; it is part of how a 2-stroke operates. The other end of the line goes to the Carb. The rise and fall of pressure on that line, moves the diaphragm in the carb, which acts as the "fuel pump".

If that impulse line is cracked or broken, you will not get gas to the carb.

I, would still take it back to the dealer. They charged you for work, that did not fix the problem... Make them warranty their service. And, you start and use the saw in front of them so they can see the problem first hand.

I don't know anything about the fuel lines and impulse lines??

 

[grsthegreat]

I just rebuilt my mantis tiller carburetor and replaced the fuel lines in it. Still wouldn't run worth cra*/... I blew out all ports and tried my best to make sure all fuel paths are clear, but that ethanol just ate up the fuel lines and gaskets and plugged it up somewhere i cannot locate.

I ordered a new carburetor off of ebay, $58.00. Not too bad considering. The part arrived today. Took 1 minute to install....fired up and runs like it was new.

No matter how hard i tried i couldn't get all the ports cleaned on the old one i guess.

From about 1 month ago on to forever, i will be only using ethereal free fuel on all my small engines. I have 2 local suppliers, and there doing booming business they tell me. It costs about $1.00 per gallon more, but i guess i really dont burn too much per season.

Over the past 6 months ive had to rebuild one manual snow-blower carb, and 2 chain saw carbs. NO MORE. This ethanol cra* has to stop. I really cant believe that our $%#&^%$ government is forcing this down our collective throats.

 

[Gobblin Tom]

I removed the decompression plug today but before I did I checked it with the new gauge, it was reading around 160-170psi and I checked it after the plug was installed and it was the same... I then tried to start the saw and couldn't get it to fire, I checked for spark and had none. My buddy checked it before and said it had spark, I tried multiple times and couldn't get a spark. I am going to try and find a coil local tomorrow but I don't think I am going to have any luck... Also I need to know how to readjust the carb so I don't lean it out and cause more problems provided I get it running again???

 

[RobertN]

How does the switch and the wiring ohm out?Sounds like you may have a short or an open, or the switch isn't operating right. Just curious how you isolated it to the coil?

I then tried to start the saw and couldn't get it to fire, I checked for spark and had none. My buddy checked it before and said it had spark, I tried multiple times and couldn't get a spark. I am going to try and find a coil local tomorrow but I don't think I am going to have any luck... Also I need to know how to readjust the carb so I don't lean it out and cause more problems provided I get it running again???

 

[Gobblin Tom]

How does the switch and the wiring ohm out?Sounds like you may have a short or an open, or the switch isn't operating right. Just curious how you isolated it to the coil?

I am going to check that wire also, the saw sits on my damp gravel garage floor and it wont start or acts funny. I left it on my porch over night and just tried to start it and it did try to fire. Have no idea how to ohm out the wire to check it? Also wouldn't the saw have to be able to run to check that?