039 issues

[zryder25]

My 039 starts and runs perfect, but only when it wants to. I thought coil because when it does run, it will just die suddenly after running a while. Then i checked and it still has spark even though it won't start again. I wouldn't think its a fuel problem because it runs perfect when it decides to run at all. And filter is new so I know its getting air. Any thoughts would be appreciated

 

[Fish]

For starters, remove the muffler and look at the piston, tell us what you see.

 

[zryder25]

i'll check that first thing in the morning, what are you thinking low compression or something

 

[Hedgerow]

i'll check that first thing in the morning, what are you thinking low compression or something

Gotta rule out running lean...
Fish knows...

 

[njforestfire]

Gotta rule out running lean...
Fish knows...

Remove the plug and look at the color it is...that'll tell you better about if it's running too lean or too rich. Does it smoke when running? What is your fuel mix ratio?

Also might want to check to see if the gas tank filter is clogged or if there is any crap in the carb.

 

[zryder25]

plug is tan, doesn't really smoke, and 50:1 mix with stihl oil

 

[fidiro]

Could it be a small crack in the fuel line that opens up more when saw heats it up some?

 

[zryder25]

Took off muffler and looked at cylinder and piston this morning, and they look factory perfect. Looked at impulse and fuel lines and they seem a bit spongy, so I'm gonna go ahead and replace them and fuel filter as well.

 

[fidiro]

Hope it works out. Keep us posted.

 

[wse8562]

The fuel line could collapsing when warm. Also check the fuel tank vent. One last thing? Did you try a new plug. Have seen plugs fail under compression but spark when tested otherwise.

 

[RiverRat2]

Took off muffler and looked at cylinder and piston this morning, and they look factory perfect. Looked at impulse and fuel lines and they seem a bit spongy, so I'm gonna go ahead and replace them and fuel filter as well.

If you have a Crankcase pressure tester you can pull the fuel filter and check the fuel line and the needle and seat valve really easy it should hold about 4-5 bar or 12-15 psi indefinitley,,, look for signs of fuel leakage between the airbox amd tghe top of the fuel tank,,, could be just a pinhole leak,,, the tester will fnd it,,,

 

[zryder25]

Finally got around to checking compression and only hit 100 psi, looks like time for a rebuild. Figure i might as well clean up the intake and exhaust a little while i got her torn down.