stihl ms261c with no spark

[plotthound]

as the title says,this saw from work suddenly quit working.i checked the plug and coil with known working plug and coil but still no spark.gapped the coil wth a buisness card when i checked it.this saw has the mtronic unit on it and i have no idea what else to check.not sure if a plugged spark arrestor would case no spark so im gonna check that next. a saw at work lasts about 2 years,so theres a pile of them here we use for parts.thanks

[plotthound]

pulled the spark arrestor out and of course it was plugged solid.cleaned it and put it back in.checked the compression and its in the 110-115 psi range.put fresh gas in it and got it to start,sputter and die,could not make it run or idle properly.checked the piston and its not scored so unless the comp is on the low side im at a standstill. thanks.

[RoyM]

You will likely have to take it to a competent dealer who can plug it into a computer.

[KE4AVB]

You will likely have to take it to a competent dealer who can plug it into a computer.

Yes it is probably a M-Tronic version.

And Roy you hit the nail on the head when you say "take it to a competent dealer". The two dealers that I buy parts cant even find a bad spark plug, let alone work on a M-tronic system.

[plotthound]

thanks for the replies. i never took it to a dealer yet but am sure its a compression problem and i would like to throw a cylinder kit in it for shiz and giggles.what brand would you recomend that i buy for this saw? thanks

[RoyM]

Go ahead if it makes you feel better but at 115psi it should run. Pistons and cylinders don't normally fail suddenly unless straight gassed and that would be readily apparent. OEM is the best for reliable service but of course is the most expensive. Meteor is alright as long as the saw is not being run hard, good for the weekend warrior. A lot of the others are pretty sketchy.

[KE4AVB]

So far in 11 yrs I have only seen one 2 cycle with great compression readings to have a bad PNC as the damage was right at the top of the stroke where engine had inhaled something. Otherwise most 2 cycle will start and run with over 100 psi compression.

115 PIS does show signs of wear but as Roy said it should run good.

[plotthound]

so i pulled the cylinder off and it is not scored or marked up,piston also has no scuff marks on it.only thing i found odd was that i could easily put the piston back in the cylinder by just compressing the rings with my fingers.so i ordered oem rings and a base gasket.will see if that does the trick.thanks

[plotthound]

so i finally received the new set of rings and base gasket.put the sucker back together and it fired right up.did the old m-tronic calibration procedure and now it runs great.thanks guys