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Mac 250 Question

Started by martyinmi, January 01, 2013, 02:30:07 PM

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martyinmi

What will cause the carburetor to spray a fine mist of fuel rearward at WOT? After I make a couple cuts through an 18" Ash there will be about 2 tablespoons of fuel in the carburetor/air cleaner box. I can pull the air cleaner off and stick a finger between the carb and the housing and the fuel will actually start running down my finger after about 5 seconds at WOT.

Keep in mind that this is not a great running saw. It makes less than 100 lbs of compression according to my local Stihl dealers tester. Mine says about 75 lbs.

I've got a 200 (just the power head) that I bought just for parts that doesn't do it.

What say you experts? :P

And I'll need your input also Al! ;) :D
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Al_Smith

Might be the reeds not fully seating .

AdkStihl

Low compression will cause spit-back.
So will a worn piston skirt on the intake side of things.
J.Miller Photography

mad murdock

Quote from: martyinmi on January 01, 2013, 02:30:07 PM
What will cause the carburetor to spray a fine mist of fuel rearward at WOT? After I make a couple cuts through an 18" Ash there will be about 2 tablespoons of fuel in the carburetor/air cleaner box. I can pull the air cleaner off and stick a finger between the carb and the housing and the fuel will actually start running down my finger after about 5 seconds at WOT.

Keep in mind that this is not a great running saw. It makes less than 100 lbs of compression according to my local Stihl dealers tester. Mine says about 75 lbs.

I've got a 200 (just the power head) that I bought just for parts that doesn't do it.

What say you experts? :P

And I'll need your input also Al! ;) :D
I thought that was the winter kit, hand warmer option ;D you are supposed to run it long enough to get a little pool of fuel in there, then if the thing is working right,  a little sparky and you get heat :D, seriously, though, pull the muff, if the piston looks good, (skirt), no scuffing, etc, then check the reeds like Al says. I hope you get it figgured out before it really does warm your hands up :)
Turbosawmill M6 (now M8) Warrior Ultra liteweight, Granberg Alaskan III, lots of saws-gas powered and human powered :D

Al_Smith

That old 250 could be a lot of things ,bad rings ,stuck rings ,funky reed valve .I doubt seriously if the piston is toast .

FWIW a sloppy piston skirt really doesn't factor into a reeder spitting back because the reed seals off any back spray or is suppossed to .You can get gunk and crude under the reed also which will cause you problems .

You can get rings for that old thing for less than 15 bucks a set ,flea bay .I looked them up today .

You get to fiddling with something made about 1962-64 you can run into a lot of things .The reeds can get warped .Simple reverse them .If that doesn't work replace them .They can be found with a little research .

AdkStihl

Yeah......reeds.
I guess I spend too much time with newer saws to even consider that.
Like Al said....check the reed petals
J.Miller Photography

Al_Smith

I guess I failed to include a fact about a 250 Mac . At 14 years of age I ran one of those things the first year they were on the market and I have 3 of the old duffers in my shed . ;)We're talking 50 years ago now .

Although they do a fairly decent job of cutting and have plenty of power it seems in my old age I have became aclimatized to lighter faster saws so they don't get much run time .Fact I have one with an 8 tooth running 3/8" 50 thou chain on a new old stock Oregon bar which is the one on Mike Acres Site .

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