EdStay

EdStay

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Apr 23, 2021
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Canada
So I'm a newbie. I've done a little bit of clearing for work, so I'm comfortable with saws. Planning on getting some vacant land soon and figured I'd need a saw to clear stuff on there/fire wood.
I have this condition where instead of buying a new, working machine, I'll buy an cheap broken machine and bang my head against it for months until I know how it works and its working. Problem is this time it bit me in the ass.
So I went to pick up this ms250 an hour from my place. The guy selling it says its ready to go, he's put in an aftermarket carb, new filter, spark plug and lines and its running well. He started it up and it was idling really high and none of the set screws were changing any of that. Red flag. But I figure I can get him to knock off $50, give me the saw and the oem carb and I can sort it out.
I order a rebuild kit for the oem carb (3 months and it hasnt come) and start pulling things apart while watching youtube teardowns. Both carbs appear to be fine, no diaphragm or gasket damage, except maybe the gasket in between the carb and the plastic housing/engine, which is a bit chewed up.
Spark plug is clean, I later regapped it just to make sure it was to spec.
The only thing I notice during the teardown is that someone did a hack epoxy job on the fuel vacuum line "nipple" that comes out of the gas tank.
With a smaller piece of plastic pipe going through to the tank holding everything in place, I super glue the plastic back together and reepoxy the outside so its strong enough to hold the vacuum line, and it seems to be working.
Saw wont start though.
So I tear it down again, and open up the engine block. Everything seems to be alright in there, minor scoring on the piston/cylinder, but nothing like ive seen on saws ive seen on the internet, and those fired up. Broke a piston ring trying to put the head back on, so I ordered and replaced both of those. Redid the liquid gasket and got the cylinder head back on.
Saw still won't fire. Spark plug has white spark and is wet, so i'm guessing its getting fuel. I cleaned out all the carbs with cleaner n compressed air and tried running with each one to no avail. I imagine its getting air. Compression test gives me 140psi, which doesn't seem unreasonable.
Still, Stihl wont go.
I'm loosing faith in my capacity to sort this thing out, but i figured before i bite the bullet and pay to have someone fix my saw I'd check with the community and see if they had any advice to help me try and sort it on my own.
Thanks in advance.
 
Overkill338

Overkill338

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You shouldn't have super glue or anything else on the fuel tank, as it will not hold. Just order the correct pieces off ebay, they are cheap.

Next, if you didn't use Motoseal or something similar to seal the motor parts back together, gas will just eat it up and you won't be getting compression on the bottom side.
 
cscltd

cscltd

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Do you mean the vent line nipple out of tank? Vacuum /impulse line goes from block to just behind inner carb/rubber airboot housing. That impulse hose may be split or not attached either end will give high idle
 
Wood Doctor

Wood Doctor

Edwin
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The MS250 is notorious for flooding. Pretty much 2 pulls on choke and then off choke even if you hear nothing. I had to learn this with mine after a few times with the plug out and upside down pulling on it to clear the fuel.
Same here. I just let it sit for half an hour or so. Mine is a 251C with the same "instant flood" problem.
 
tomalophicon

tomalophicon

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Carb fuel screws? After I rebuilt my carb I thought I'd seated the screws all the way in when it was off the saw. But when the carb was installed they were still 4 turns out. It wouldn't start and was getting flooded. AS soon as I adjusted the screws correctly she fired right up no worries at all.

I think most would recommend 1.25 turns out from fully seated to start with.
 
EdStay

EdStay

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Do you mean the vent line nipple out of tank? Vacuum /impulse line goes from block to just behind inner carb/rubber airboot housing. That impulse hose may be split or not attached either end will give high idle
yeah the one coming out of the tank had broke off. the line looks new. i imagine it was the bad epoxy job he did that could have been causing his high idle, but thats "fixed" now and the saw wont start...
 
EdStay

EdStay

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You shouldn't have super glue or anything else on the fuel tank, as it will not hold. Just order the correct pieces off ebay, they are cheap.

Next, if you didn't use Motoseal or something similar to seal the motor parts back together, gas will just eat it up and you won't be getting compression on the bottom side.
thankfully it was motoseal, so I think its good in that regard.
it seems to be holding up pretty well with the krazy glue joining the broken pieces and hardened around the outside, but yeah, not ideal. if it fails again or i run out of other possible issues i'll replace it, but with these models the tank is fabbed into the rest of the housing so i'd have to drop $50 to replace the entire thing, which id like to avoid...
 
EdStay

EdStay

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Carb fuel screws? After I rebuilt my carb I thought I'd seated the screws all the way in when it was off the saw. But when the carb was installed they were still 4 turns out. It wouldn't start and was getting flooded. AS soon as I adjusted the screws correctly she fired right up no worries at all.

I think most would recommend 1.25 turns out from fully seated to start with.
could be. I reset all the set screws to spec from the manual (thanks to beg for manuals thread), but I'll double check them next time I'm feeling optimistic and try to run the saw.
 
EdStay

EdStay

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The MS250 is notorious for flooding. Pretty much 2 pulls on choke and then off choke even if you hear nothing. I had to learn this with mine after a few times with the plug out and upside down pulling on it to clear the fuel.
Doubles as a portable shower eh? I'll keep this in mind when I run the saw, thanks.
 
cscltd

cscltd

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the nipple on tank issue will only cause 2 problems
1- will leak fuel out of tank-will not effect starting-but safety, or wet pant leg issue
2-will stop tank from venting-will not effect cold starting, only will cause issue like high idle, staling, or hot starting after unit is running for 5-10 min
the nipple repair is not the issue for your no start problem
 
lone wolf

lone wolf

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the nipple on tank issue will only cause 2 problems
1- will leak fuel out of tank-will not effect starting-but safety, or wet pant leg issue
2-will stop tank from venting-will not effect cold starting, only will cause issue like high idle, staling, or hot starting after unit is running for 5-10 min
the nipple repair is not the issue for your no start problem
He needs to pressure test it.
 
EdStay

EdStay

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Messages
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Canada
the nipple on tank issue will only cause 2 problems
1- will leak fuel out of tank-will not effect starting-but safety, or wet pant leg issue
2-will stop tank from venting-will not effect cold starting, only will cause issue like high idle, staling, or hot starting after unit is running for 5-10 min
the nipple repair is not the issue for your no start problem
Thanks! That’s reassuring, and confirms why it was acting funky when he ran it for me. What the hell is wrong with it now I wonder...
 
cscltd

cscltd

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you can visually check impulse line without pressure vac test, if impulse line good, then pressure vac test next step
or severely flooded-no choke full throttle lock and 30 pulls on rope to clear. can pinch fuel line is suspect carb flooding while sitting/running
 
EdStay

EdStay

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Thanks for all the advise guys. She’s up and running. In the end it came down to an janky jury rig I didn’t realize the previous owner had done. After loosing the choke rod numerous times after I noticed it wasn’t engaging the carb correctly. A closer inspection and comparison with the ipl revealed this to be a piece of wire someone had shaped into a replacement. After manually operating the valve I was able to get it started. Replacement rod on the way. $6 for an inch of wire they got me again!
Still, yesterday was a good day. Should be slicin and dicin in no time. Thanks again for the support.
 

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