346, running funny, and a vacuum test question.

[Westboastfaller]

And the truth shall set you free.

 

[Big_Wood]

a slow drop like that could be a leak in your block offs at the muffler and intake depending on what you used. it could also be a slow weep in a seal but pulling vacuum on them would rule that out as they will leak worse on vac. this saw will have the zama on it and if the carb has not been rebuilt do it. the pump diaphragm is a POS in these carbs and last 2 i had struggled to feed the metering side of the carb. a carb kit will fix it up but you'll still have that same POS diaphragm, it'll just be new lol . yer talking 1 PSI in near 30 seconds. that's not even enough to make tuning an issue and points at your block off plates being the most likely spot for that slow weep. you should also know, the impulse design on these 346's is almost as goofey as the impulse design on a 55 husky (well not quite lol) a nipple in the intake partition slips through the section of the boot and the rubber of the boot is the seal BUT it can still leak between the plastic nipple and boot. it's just a bogus design when they could just do the bullet proof external line like on the 372/390/395. i'd rebuild the carb, tune, and run the living piss out of the thing.

 

[Jules083]

a slow drop like that could be a leak in your block offs at the muffler and intake depending on what you used. it could also be a slow weep in a seal but pulling vacuum on them would rule that out as they will leak worse on vac. this saw will have the zama on it and if the carb has not been rebuilt do it. the pump diaphragm is a POS in these carbs and last 2 i had struggled to feed the metering side of the carb. a carb kit will fix it up but you'll still have that same POS diaphragm, it'll just be new lol . yer talking 1 PSI in near 30 seconds. that's not even enough to make tuning an issue and points at your block off plates being the most likely spot for that slow weep. you should also know, the impulse design on these 346's is almost as goofey as the impulse design on a 55 husky (well not quite lol) a nipple in the intake partition slips through the section of the boot and the rubber of the boot is the seal BUT it can still leak between the plastic nipple and boot. it's just a bogus design when they could just do the bullet proof external line like on the 372/390/395. i'd rebuild the carb, tune, and run the living piss out of the thing.

Thanks.

I'm using cut up motorcycle tubes to block the intake and exhaust. So they could very well be leaking.

A carb rebuild probably is in order. I've read a few other posts elsewhere talking about these carbs being problematic.


Sent from my iPhone using Tapatalk

 

[SEAM]

If it did run good the first 10 minutes I would check if the fuel tank vent is blocked... Run the saw until the problems start, stop the engine and unscrew the tank lid once. Try to start the engine after that. If it runs normal the vent is clogged.

 

[Jules083]

If it did run good the first 10 minutes I would check if the fuel tank vent is blocked... Run the saw until the problems start, stop the engine and unscrew the tank lid once. Try to start the engine after that. If it runs normal the vent is clogged.

I bet that's the problem. I remember pulling the cap and hearing a hiss. I'll check tomorrow.


Sent from my iPhone using Tapatalk

 

[Big_Wood]

If it did run good the first 10 minutes I would check if the fuel tank vent is blocked... Run the saw until the problems start, stop the engine and unscrew the tank lid once. Try to start the engine after that. If it runs normal the vent is clogged.

Good catch. I didn't even notice he said it ran good for 10 min

 

[Jules083]

Wanted to bring some closure to the thread.

I fiddled around with the vacuum tester for a long time, and got to the point where the leak was extremely slow. Like a pound every 2-3 minutes. I figure that amount was somewhere in my blockoffs rather than a seal itself, so I put the saw back together.

Paid close attention, took my time, and made sure everything went together correctly. Started it up, put a screwdriver in my pocket, and started cutting. I've now ran 6 or 8 tanks of gas through it with no problem. Best I can figure is a vent was blocked, or maybe a hose kinked? Dunno. Either way it's running fine now. Never did get around to doing a compression test, but it feels fine.


Sent from my iPhone using Tapatalk

 

[Full Chisel]

Glad you got it running good. Tank vent was my first guess from your description. Enjoy your 346!

 

[redunshee]

Glad you got it running good. Tank vent was my first guess from your description. Enjoy your 346!

That's why I Always pressure test and vac test the tank and vent lines. If fuel tank holds pressure your cap is not leaking. If it holds vacuum your vent line is clogged.

 

[Agrarian]

Was having some problems with my 372, decided I needed another chainsaw for my growing CAD and bought a 346xp off eBay. Always wanted one.

First thing out of the way. I'm vacuum / pressure testing it right now. If I pressurize the crankcase to 10psi it drops to 9 psi in 25-30 seconds. I think the leak may be in my decompression valve plug, as I had to use a bolt with a homemade tubing spacer to get it plugged. Is that an acceptable loss, or do I need to stop and buy a better bolt plug for another attempt? I don't know where the leak is for sure, or how fast a good saw will leak down. This is my first time testing.

The plugs are cheap on eBay and may even be at your local plumbing supply. I always have to put a little LocTite on the threads of the plug to get it to seal when I do vac/pressure testing.