modded MS 170 dying

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Greymakesstuff

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Hey guys, I recently did some modifications to a MS170 (ported to 150 degrees on both sides, muffler mod and timing advance) that I got for parts from work because the spark plug hole was stripped, which I heli coiled and did all the mods I wanted to do. Anyways I got it all back together and it will start (and it just screams!) but after a few seconds it bogs down and dies even at idle. The heli coil was leaking because I did'int use any thread locker:rolleyes: but i fixed this by putting an old plug in half way and silver soldering around it. I also cleaned the carb and made sure the fly wheel was not slipping. Another thing is it does'int have a fuel filter/pickup on it because the stihl dealer (where I work) is closed for the long weekend does the saw need this? and i was very careful not to get any crap in the tank!
any ideas?
 
Hey guys, I recently did some modifications to a MS170 (ported to 150 degrees on both sides, muffler mod and timing advance) that I got for parts from work because the spark plug hole was stripped, which I heli coiled and did all the mods I wanted to do. Anyways I got it all back together and it will start (and it just screams!) but after a few seconds it bogs down and dies even at idle. The heli coil was leaking because I did'int use any thread locker:rolleyes: but i fixed this by putting an old plug in half way and silver soldering around it. I also cleaned the carb and made sure the fly wheel was not slipping. Another thing is it does'int have a fuel filter/pickup on it because the stihl dealer (where I work) is closed for the long weekend does the saw need this? and i was very careful not to get any crap in the tank!
any ideas?
Timing could be out.
Dont think the carb is adjustable, so after your mods it’s running lean,
have you looked if there are scores on the piston, take off muffler and look in.
Fuel line could be floating, wrap some copper wire or such around the end to sink it.
 
don't think the timings out I've seen other people do a timing advance more than I did but i might of gaped it wrong what distance do you like? and your right the carb is non adjustable thinking of upgrading to a wt-215 in the future. there is some scoring but very little. ill try the fuel line thing-thanks! another thing I was thinking is that i did'int re seal the crank case just left the old stuff because it looked ok do you think it could be sucking air through there and not getting enough fuel? and there is some fuel mist coming out the intake when the cover is off is this because air that's getting sucked through the crank case is in the way so the fuel/air mix is coming out the intake instead or is this normal?
 
don't think the timings out I've seen other people do a timing advance more than I did but i might of gaped it wrong what distance do you like? and your right the carb is non adjustable thinking of upgrading to a wt-215 in the future. there is some scoring but very little. ill try the fuel line thing-thanks! another thing I was thinking is that i did'int re seal the crank case just left the old stuff because it looked ok do you think it could be sucking air through there and not getting enough fuel? and there is some fuel mist coming out the intake when the cover is off is this because air that's getting sucked through the crank case is in the way so the fuel/air mix is coming out the intake instead or is this normal?
I know nothing of timing the saw, other than it can go wrong, but as you have said
you didn’t go as far as others, then timing is probably ok.

Not cleaning and re sealing the case is big trouble, vacuum and pressure test required.

Fuel coming up into the intake is usually too much fuel being supplied to the engine,
but worn piston skirt causes it too, given the carb is not adjustable its unlikely too
much fuel, but could be flooding and shutting you down.

Scoring on the piston is bad, if it is very slight then a fine sanding can fix it,
I use a large nail file and try to start on a surface that has no build up or score
and work towards the shores and buildup, carefully filing only the high parts,
then use fine paper to smooth it off.

I used a wood chizzel a time or two to slice off buildup, it has to be razor sharp
as does your eyesight, and no shakes either, not advising it unless you understand
the principle and the danger, but it worked for me.

Check your cylinder for aluminium transfer from the piston, there are ways to remove
that too.

Was the piston scored when you got the saw, if so you should have sorted it, it only
ever gets worse.
 
the cylinder was mint when i first got it but i did score it a bit when porting :angry: i re sealed it and there was some aluminium flakes in it might be wrecked
Ok, that sucks, hopefully it will clean up.
Believe it or not, I got criticised for spending too much time cleaning engines
that had cylinders bored, heads skimmed, and shafts ground, did I listen,
no, I am still meticilus in cleaning.
 
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