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

[PogoInTheWoods]

Agreed on compression not being the problem here. And a bad tank vent wouldn't make it run richer, it would starve it. That said, I'd like to see pics of the 'vent' location and how the vent is actually installed just for grins since there were a couple tank variations and vent orientations among these saws..., and there is the purge (primer?) bulb in the mix. And no one has mentioned the throttle linkage as a possible source of the RPM limitation, though being able to run this saw with the 'H' screw all the way in is a whole other issue to contemplate. I do believe I'd also try to find yet another coil to try for an additional comparison there.

As an aside, there's a reason these saws have a decomp, and 140psi ain't it. If my stock NE346xp was only blowing 140-ish, I'd be tearing it down to find out why (after grabbing another compression gauge to actually confirm such a reading). I'd also respectfully suggest that leaky decomp valves and plug seats are often as much to blame for lower than expected compression as carbon buildup or oil residue is for higher than 'normal' readings. It's not normally to the same extent, but can still be a factor. Not trying to be contentious here, just offering a personal observation based on a certain level of experience..., mostly gained by learning things the hard way in the first place. LOL

 

[beaglebriar]

Agreed on compression not being the problem here. And a bad tank vent wouldn't make it run richer, it would starve it. That said, I'd like to see pics of the 'vent' location and how the vent is actually installed just for grins since there were a couple tank variations and vent orientations among these saws..., and there is the purge (primer?) bulb in the mix. And no one has mentioned the throttle linkage as a possible source of the RPM limitation, though being able to run this saw with the 'H' screw all the way in is a whole other issue to contemplate. I do believe I'd also try to find yet another coil to try for an additional comparison there.

As an aside, there's a reason these saws have a decomp, and 140psi ain't it. If my stock NE346xp was only blowing 140-ish, I'd be tearing it down to find out why (after grabbing another compression gauge to actually confirm such a reading). I'd also respectfully suggest that leaky decomp valves and plug seats are often as much to blame for lower than expected compression as carbon buildup or oil residue is for higher than 'normal' readings. It's not normally to the same extent, but can still be a factor. Not trying to be contentious here, just offering a personal observation based on a certain level of experience..., mostly gained by learning things the hard way in the first place. LOL

Great post.

I'd really like to have this saw on my bench. That's the only way to give it a good diagnosis at this point. There's only so much that can be wrong with these things.

 

[decableguy2000]

And no one has mentioned the throttle linkage as a possible source of the RPM limitation

I did have an issue there, found the end of the linkage had come off and was stuck in the handle (used tank) ,resolved that problem. Thought the rod may be bent and reached in the carb box and opened all way, still no 13k. Old style tank vent with the pills. OE 42mm with no decomp.

 

[decableguy2000]

This is a parts pile build, only new parts are a ring, plug, carb kit on one carb and one new carb, partition wall, clamp, plug, top cover, starter decal. fuel line, tank vent (I think) and filter. If it will quit raining, I may get a chance to part swap some more, have one more unlimited coil and another rebuilt carburetor.

 

[beaglebriar]

This is a parts pile build, only new parts are a ring, plug, carb kit on one carb and one new carb, partition wall, clamp, plug, top cover, starter decal. fuel line, tank vent (I think) and filter. If it will quit raining, I may get a chance to part swap some more, have one more unlimited coil and another rebuilt carburetor.

Coils will do some crazy chit. Have you swapped it out before?

 

[PogoInTheWoods]

Is the fuel line OEM? I only ask because there have been issues with the Tygon LP series line which has an additional interior membrane lining the actual hose. It separates from the main hose and essentially clogs the line. It's typically found on the cheaper homeowner OPE but is also out there as bulk line in various sizes nonetheless.

 

[decableguy2000]

Coils will do some crazy chit. Have you swapped it out before?

yes with a limited one

Is the fuel line OEM?

Yes it is OEM

 

[smokey7]

The first topend was a 44mm open port. The second was a fast n nasty by the dealer somehow using a 44.3 jug with no markings and a 44mm piston. It ran but like total crap. Then i put a oem 346 ne topend on it.

 

[andyshine77]

Agreed on compression not being the problem here. And a bad tank vent wouldn't make it run richer, it would starve it. That said, I'd like to see pics of the 'vent' location and how the vent is actually installed just for grins since there were a couple tank variations and vent orientations among these saws..., and there is the purge (primer?) bulb in the mix. And no one has mentioned the throttle linkage as a possible source of the RPM limitation, though being able to run this saw with the 'H' screw all the way in is a whole other issue to contemplate. I do believe I'd also try to find yet another coil to try for an additional comparison there.

As an aside, there's a reason these saws have a decomp, and 140psi ain't it. If my stock NE346xp was only blowing 140-ish, I'd be tearing it down to find out why (after grabbing another compression gauge to actually confirm such a reading). I'd also respectfully suggest that leaky decomp valves and plug seats are often as much to blame for lower than expected compression as carbon buildup or oil residue is for higher than 'normal' readings. It's not normally to the same extent, but can still be a factor. Not trying to be contentious here, just offering a personal observation based on a certain level of experience..., mostly gained by learning things the hard way in the first place. LOL

I don't think you're being contentious in any way, you're just sharing your experience. My experience has just been slightly different with this series of saws. Like I said before I've seen all the way down to 135psi on a 353, they tend to have a bit less compression than the 346's I've been in. I personally have never seen the need for a decomp valve in a 50cc saw, even with above stock compression, I suppose it does put sless stress on the starter assembly.

As for this saw I'm at a loss. I'll throw a few things out for you to check. Could the engine have something restricting flow? like the base gasket blocking off part of a transfer tunnel. Double check to make sure the carb is opening all the way, seen this happen at a gtg, saw wouldn't rev past 11,00 rpm. Also make sure the spring in the spark plug boot is making good contact with the wire and plug itself.

 

[decableguy2000]

Could the engine have something restricting flow?

You may on to something there. I don't like reusing gaskets, but I may still have an OEM base gasket and ring from when I sourced these parts. Suppose to rain again this evening so its a maybe if get to it.

 

[Chainsaw Jim]

I've been told there's at least one black limited coil out there and it wouldn't surprise me if it came on the 365. I'm wondering if both coils you tried are limited at the same rpm.

 

[decableguy2000]

Blue one from a NE 346 14100 limit

 

[XP_Slinger]

I've been told there's at least one black limited coil out there and it wouldn't surprise me if it came on the 365. I'm wondering if both coils you tried are limited at the same rpm.

Didn’t the 375K have a black limited coil?? I may be recalling it wrong

 

[decableguy2000]

Didn’t the 375K have a black limited coil?? I may be recalling it wrong

I thought they were green.

 

[Termitebuffet]

Dumb question, you did remove the limiters from the carb ....right ?

Sawhawgz, ruining the internet since 2012...

 

[andyshine77]

I thought they were green.

I believe they were in fact green. Pretty sure all the black coils were unlimited, and if they were limited the max rpm should be marked on the coil.

 

[XP_Slinger]

I thought they were green.

That’s what it was, thank you. Sorry to distract with a brain fart

 

[huskyboy]

Coils will do some crazy chit. Have you swapped it out before?

I had a 390xp run backwards from a really “retarded” coil.

 

[PA Dan]

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

Ok what is this and where does one get some?

 

[beaglebriar]

eBay... echo tank vent [emoji106]