My new ms170 with problems

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kugss

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I got a new to me ms170 (Stihl MS 170 14" Chainsaw for parts not working - eBay (item 280712201791 end time Jul-26-11 15:51:45 PDT)) was told it was low on comression. When the ups guy drops it off today i tear open the box to see what awaits me. Its kinda dirty but not beat to death yet, the muffler is losse like it was removed to look at the piston. Finger tight so take a look at the piston not a scuff to be seen but lots of carbon about 20% of the exhaust port is closed off. I clean off the piston and the exhaust port with some seafoam and carb cleaner give the whole saw a good cleaning . So at this point im kinda confused. so i do a compression test and get 103# cold with about 6 pulls and the fast idle set. Is 103# enough? My comp tester is a mac pro one with every adapter and hose only used about 25 times. I cant get this thing to run or even sputter. The plug is getting wet after about 10 pulls and its got great blue spark. I guess it time for rings. Whats AS have to say?
 
that is low,, i think that one should be around 140,,, yo might bet lucky and the rings are just carboned up and stuck in the groove,, if thats the case just replace the ring
 
Your compression is low but that is enough to make it run. It will be low on power but should run. When the piston is at TDC is your magnets lines up with your coil?
 
I just got done tearing it apart and the rings are stuck so bad that they are breaking when i try to remove them. Almost like the thing whas hydrolocked and it smashed the piston down on the ring lands. So i guess its time for a rebuild.
 
Northwood Saw has the Episan piston and rings for about $30. Another $3 gets you the oil seals. Add a little shipping and you're in about $40. Might need new fuel line and filter though. Have fun. I just completed a rebuild of one of those blown up saws.
 
roostersgt said:
Northwood Saw has the Episan piston and rings for about $30. Another $3 gets you the oil seals. Add a little shipping and you're in about $40. Might need new fuel line and filter though. Have fun. I just completed a rebuild of one of those blown up saws.
Click to expand...

I have this setup in one of mine. The saw has about 10 tanks on it and still running strong. I would add seals for piece of mind. They are cheap.
 
The piston, rod and cylinder all look great crank seals are not a bad idea while im in there.
 
With all that carbon it looks like it was set too rich, too much oil in the mix, idled too much and not run hard enough. A chunk of carbon may have broke off, got on top of the piston and hammered the rings tight. Steve
 
Its a ms 170 throw it and buy a new one! they are only $299 in australia that would make them like $150 in the states! the time wasted putting a new p&c would cost you that!
 
masculator said:
Its a ms 170 throw it and buy a new one! they are only $299 in australia that would make them like $150 in the states! the time wasted putting a new p&c would cost you that!
Click to expand...

Time doesn't matter for a lot of us, more of a hobby and the satifaction of getting something running. They are $159 on sale $179 regular. Steve
 

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