Husqvarna 359 Won't Run Rich Enough

[ndlawrence]

Hi All,

At the end of last summer, my 359 was starting to get a little bit hard to start, not idling as smoothly as it should. I figured it was time to rebuild the carb. I ended up replacing the piston, crank bearings & seals, fuel hose, air filter, & installed carb kit. Back altogether and the saw starts and idles well, but I can not get the saw to run rich enough @ WOT. I can back the high speed screw out all the way with no effect. It is running way lean.

Things I have checked:

• Pressure & vacuum tested for air leaks. No leaks.
• Pressure tested carb. No leaks @ 7psi.
• Checked metering arm height.
• Checked diaphragm placement.
• Checked impulse line for obstructions. It seams to be clear. It will cause about a +/- 1psi on the Mity Vac when turning the saw over.

It seems to me to be an issue with the high speed circuit?... I've been through the carb twice. Not sure what to check next.... Any input is appreciated.

 

[Wood Doctor]

I never seem to have much luck rebuilding carbs. You've replaced about everything else. Might as well replace the carb with a new one and see if that solves it. I think it's a worthwile $14 gamble to see if an aftermarket carb works. Dimes to donuts it will.

 

[Jasent]

Definitely sounds like a problem with that high jet

 

[cookies]

this past year i have experienced many problems with aftermarket carb kits, mostly in the diaphragms producing too low of a fuel volume and the wrong spring/lever and needle. if you used a non zama/walbro kit I would start there then pressure/vac test everyting.

 

[farmguywithasaw]

Fuel line? Filter? Did you check them. Make sure it’s not pinched somewhere

 

[Old2stroke]

When you rebuilt the carb, which fuel pump diaphragm did you use? The stiff plastic (acetate) one is the worst for fuel delivery, the rubbery one is the best and the tan (teflon) one is a best compromise for longevity and fuel delivery. I've had a lot of grief with the plastic ones just not delivering enough fuel for full power.

 

[hotshot]

+1
No mention of a new OEM fuel filter or what material the OEM carb’s pump side diaphragm was made of. Nitrile, acetate, or teflon weaves?

Most manufacturers state to renew the gas filter annually.

 

[ndlawrence]

Fuel line? Filter? Did you check them. Make sure it’s not pinched somewhere

Yes. I replaced fuel line and filter, albeit not with oem.

When you rebuilt the carb, which fuel pump diaphragm did you use? The stiff plastic (acetate) one is the worst for fuel delivery, the rubbery one is the best and the tan (teflon) one is a best compromise for longevity and fuel delivery. I've had a lot of grief with the plastic ones just not delivering enough fuel for full power.

It is the tan one. It was a walbro kit.

 

[rmh3481]

Raise the lever.

 

[J D]

If the metering diaphragm vents back to the air filter a blockage there could cause it to run lean. You can tell by the spacer & the cover having no vent hole. Those carbs have a diaphragm/gasket with a small hole near the edge for venting (your new ones may just be missing the hole). That system was never the best & converting it to vent to atmosphere can be the cure for several issues including some of your original problems

 

[ndlawrence]

If the metering diaphragm vents back to the air filter a blockage there could cause it to run lean. You can tell by the spacer & the cover having no vent hole. Those carbs have a diaphragm/gasket with a small hole near the edge for venting (your new ones may just be missing the hole). That system was never the best & converting it to vent to atmosphere can be the cure for several issues including some of your original problems

Bingo! I used the K22-HDA kit, which is missing the hole. I drilled it out and drilled a hole in the diaphragm cover. Saw runs flawless now. Thanks everyone!

 

[Vintage Engine Repairs]

Bingo! I used the K22-HDA kit, which is missing the hole. I drilled it out and drilled a hole in the diaphragm cover. Saw runs flawless now. Thanks everyone!

Hey mate, can you upload a few pictures of exactly what you and JD are talking about? Just want to learn from this. Cheers

 

[ndlawrence]

Hey mate, can you upload a few pictures of exactly what you and JD are talking about? Just want to learn from this. Cheers

Here is a video. Even better!

 

[Vintage Engine Repairs]

Here is a video. Even better!

Ah thank you I see, it’s just at atmospheric vent hole that gets blocked by the diaphragm and gasket.

 

[J D]

Bingo! I used the K22-HDA kit, which is missing the hole. I drilled it out and drilled a hole in the diaphragm cover. Saw runs flawless now. Thanks everyone!

Glad you got it sorted. When I drill the cover I remove the plastic spacer & use the outer gasket so it seals the hole to prevent any crud traveling back into the air filter.
@Gaudaost ... The vent hole goes back to the inside of the filter rather than atmosphere. The idea is that as the filter gets blocked the vacuum created reduces the fuel to compensate. In reality the passage is too restrictive & causes other issues to varying degrees. Simple solution is to vent back to atmosphere like most carbs do by drilling the cover.