346 OE intermittent bog, won't reach 13k RPM, Revisited FIXED!!!

[decableguy2000]

I assembled this saw from new and used OE parts a few weeks ago. Was cutting some dead yellow pine and I could make 3 cuts than it would bog, make a cut bog, 3 more than bog. Pressure and vacuum tested good when I reassembled, new Zama EL18, new intake, vacuum line, New Caber ring, and aftermarket base gasket. New plug, tank vent, and fuel line (I think, have 4 saws on bench). I have a few extra parts to try and swap if need be. I'm thinking fuel related but, I can not confirm or deny.

 

[Keith Gandy]

Tank vent isnt venting it sounds like. That would be my first stop

 

[RIDE-RED 350r]

Just for the sake of redundancy, try running it without the fuel filter. I had a head-slapping moment with my 242 awhile back regarding a fuel filter that looked descent enough but didn't flow enough.

 

[decableguy2000]

A little more diagnostics, not carburetor, swapped the one from my 351, same symptom. Can't get saw above 12.8k rpm even with the high all the way in. Put the new carb on the 351 and turning 13000 3/4 turns out. Time to dig through my miscellaneous spare parts. I may have got some stuff mixed up. I have some farmertec fuel filters that came in the other day but I have not ran them yet in any thing.

 

[decableguy2000]

Same symptoms, with new OEM fuel line and after market filter. Pulled the tank vent pills and hosed them off with some carb cleaner and reinstalled ( thought I had and extras but can't find them). Still no 13k rpm.

 

[RIDE-RED 350r]

Wtf.....sure sounds like a fuel delivery issue to me. Head scratcher

 

[andyshine77]

Some of the tanks didn't have the hole for the vent properly drilled out, so I'd vac test the tank. Just make sure the tank is empty before you hook up the vac to the fuel line.[emoji4] been there done that lol.

 

[decableguy2000]

Tried the coil for giggles, still no change. Waiting on tank to dry out now.

 

[beaglebriar]

I'd check all the impulse stuff just for chit's and giggles.

 

[cus_deluxe]

A little more diagnostics, not carburetor, swapped the one from my 351, same symptom. Can't get saw above 12.8k rpm even with the high all the way in. Put the new carb on the 351 and turning 13000 3/4 turns out. Time to dig through my miscellaneous spare parts. I may have got some stuff mixed up. I have some farmertec fuel filters that came in the other day but I have not ran them yet in any thing.

Im cornfused, is this a lean bog? From the part in the middle of this post, it would seem like you think its getting too much fuel since u turned the H all the way in?

 

[cus_deluxe]

Pressure and vacuum tested good when I reassembled

Have you done this again since it started acting up?

 

[decableguy2000]

Im cornfused, is this a lean bog? From the part in the middle of this post, it would seem like you think its getting too much fuel since u turned the H all the way in?

Me too. While cutting it would bog down, pull it out of the cut and it would pick back up and was able to make 3 bucking cuts and do it again, I was thinking it was maybe flooding out, but I tried 3 different carbs, 1 new and 2 rebuilt, the carb works fine on my 351.

Have you done this again since it started acting up?

Not yet, was planning on doing it some time today or tomorrow, after I verify tank vent is working properly.

 

[Keith Gandy]

Me too. While cutting it would bog down, pull it out of the cut and it would pick back up and was able to make 3 bucking cuts and do it again, I was thinking it was maybe flooding out, but I tried 3 different carbs, 1 new and 2 rebuilt, the carb works fine on my 351.



Not yet, was planning on doing it some time today or tomorrow, after I verify tank vent is working properly.

Im putting money on the tank vent. I had a 390 do the exact same and it was a partially plugged vent that was starving the saw after a few cuts

 

[Chainsaw Jim]

Is the muffler screen clean?

 

[decableguy2000]

Tank wont hold pressure or vacuum???!!! O vacuum, can build some pressure but not like the manual says.

 

[decableguy2000]

Is the muffler screen clean?

yes

Have you done this again since it started acting up?

90% that is good, my plug adapter is leaking per the bubbles, need to make a new one. However these are numbers I have for now Pressure 10psi to 9 in 2.5 minutes, vacuum 10hg down to 7.5 in 2 minute range.

Replaced the impulse hose today, pulled the cylinder and verified the impulse route. Managed break the intake where choke rod runs through it. I'm going to ordera ne carburetor flange, due the fact I'm wearing out pulling and swapping the carburetor

 

[beaglebriar]

It does have the metal clamp on the intake correct?

 

[andyshine77]

Tank wont hold pressure or vacuum???!!! O vacuum, can build some pressure but not like the manual says.

View attachment 121705

The tank should not hold any vacuum if the vent is working properly.

 

[decableguy2000]

It does have the metal clamp on the intake correct?

Yes

 

[beaglebriar]

Drill the vent out and put on of these in it. Then you'll know it's working properly.