Stihl 045 dies mid cut

[popopboat]

My friend gave me his 045 to "take a look".

Starts fine, idles perfectly, and abot 2 seconds in the cut it just bogs down, if throttle released, it will idle and after few seconds can cut for 2 seconds again. (doesnt just die, but booooogs)

Tipical bad impulse line symptoms, right? Nope.

Idles perfectly no matter the orientation,
Impulse line is not leaking,
fuel line is not cracked nor leaking,
membrane/diaphragms are like new,
intake boot is not leaking,
same thing with fuel cap removed,
oil seals are fine...

Im running out of ideas, am i missing something ?
Its a b-word to dissasemble to go part by part diagnostics.

 

[BlackCoffin]

Have not diagnosed, but my 064 just started doing the same thing so following for ideas.

 

[drf256]

Tank vent? I know, but are you really running with tank open?

Also, coils do weird stuff under load. Change spark plug, a heated chamber has much more resistance in a plug. I’ve been burned by this before.

Fuel line not cracked, but they can soften an suck closed. Is the fuel filter ok? Screen in carb clean?

 

[Pincher]

I have been burnt by carb diaphragms that seem to be ok to reuse but weren't. This was on a MS250 that had similar symptoms. Even though the diaphragm was pliable, it was deformed enough to affect the metering lever and valve.

 

[popopboat]

Fuel line not cracked, but they can soften an suck closed.

Damn! This is it! Thank you.
Tried running it without fuel filter and the problem is solved! Starts even easier and actually runs.

I mean, that thing came across my mind, but fuel filter was clean very clean, so i doubted it was that simple.