Carburetor talk - fuel puddling

[Sloughfoot]

,

 

[Sloughfoot]

I've never replaced a nozzle. Just punch the old one out and tap a new one in?

 

[hacskaroly]

I've never replaced a nozzle. Just punch the old one out and tap a new one in?

I messed with one on one of my Husky saws, can't remember which brand, but yeah, use a punch the same size (or close) as the nozzle and tap it out. Do the same to tap it (or a new one) back in. Not sure if newer carbs have this option, might be just some of the older ones where you had more options to do more.

 

[Sloughfoot]

I messed with one on one of my Husky saws, can't remember which brand, but yeah, use a punch the same size (or close) as the nozzle and tap it out. Do the same to tap it (or a new one) back in. Not sure if newer carbs have this option, might be just some of the older ones where you had more options to do more.

Got a carb now that's doing everything right but putting fuel in the venturi. Thinking it may have a clogged nozzle.

 

[jacktheripper]

Very cool, I wonder what the nozzle issue was, something clogging/partially clogging or maybe erosion creating a larger opening? I wonder if a pass through an ultrasonic cleaner will restore the nozzles to new.

I think that the issue is with the check valve material inside of the nozzle. It must seal tightly at idle, and allow fuel to flow freely past it under throttle. The material is similar to what those brown colored diaphragms are made out of. It can go bad due to years of not running or exposure to ethanol.

 

[Sloughfoot]

I think that the issue is with the check valve material inside of the nozzle. It must seal tightly at idle, and allow fuel to flow freely past it under throttle. The material is similar to what those brown colored diaphragms are made out of. It can go bad due to years of not running or exposure to ethanol.

On the carb I'm having issue with, there was a round piece of thin transparent film floating around on that side.

 

[jacktheripper]

On the carb I'm having issue with, there was a round piece of thin transparent film floating around on that side.

Yep, that’s the check valve

 

[jacktheripper]

It is absolutely necessary for that to be present and functional for the saw to idle correctly

 

[EFSM]

I have an update on all of this. I ordered two new nozzle/check valve assemblies for my saws and installed them on my HD-14 and HD-16. Lo and behold, the fuel puddling issues are gone. Idle fluctuations are gone. Throttle hesitation is gone.

If you are having issues with your HD series carb, try a new nozzle.

I have seen Walbro’s black rubber check valves swell and plug the nozzle due to ethanol exposure, but I can’t recall ever having issues with the tan Mylar ones.

It is absolutely necessary for that to be present and functional for the saw to idle correctly

If it isn’t working, air is pulled back to the metering chamber at idle. Thankfully, a non-primer system doesn’t need a check valve on the idle circuit. Zama trimmer carbs have too much trouble with the idle check valves, which are non-serviceable (pressed into a blind hole under the metering lever).

 

[Wonkydonkey]

I,d be very interested to see if someone else can fix the same issue of fuel pudding etc. and fix it with a new check valve.

Btw it maybe be worth linking a thread on how to change a check valve

 

[Ketchup]

IIRC, Walbro put out a service bulletin some years ago saying NOT to put their carbs in an ultra-sonic cleaner.

 

[singinwoodwackr]

I have an update on all of this. I ordered two new nozzle/check valve assemblies for my saws and installed them on my HD-14 and HD-16. Lo and behold, the fuel puddling issues are gone. Idle fluctuations are gone. Throttle hesitation is gone.

If you are having issues with your HD series carb, try a new nozzle.

Where did you get them?

 

[jacktheripper]

Where did you get them?

Here’s the ones I bought. They’re out of stock now.

Stihl OEM Carburetor Valve Jet HD-17 / 15 MS440 440 044 1128-121-5405 #GM-P1A7 | eBay

This is a Stihl. Walbro Carburetor Valve Jet. MS 440-R Magnum (Carburetor HD-15, HD-17). MS 440-VW Magnum Arctic (Carburetor HD-15, HD-17). MS 440 Magnum (Carburetor HD-15, HD-17). MS 460-R Magnum (Carburetor HD-15, HD-17).

ebay.us

 

[Funky sawman]

Whats the best way to change the main nozzle? Special tools?

 

[Sloughfoot]

Whats the best way to change the main nozzle? Special tools?

post #43

 

[jacktheripper]

Here is a video I made for another member who was helping me diagnose this carb. You can see the hole where the nozzle was. It must be aligned in the correct orientation when punched back in. I just use a regular tapered punch and a hammer. Set the carb body on a block of wood so you don’t damage it.

The check valve in the nozzle can be pressure tested. Simply push pressure into it from the Venturi side and see if it holds. Make sure the recessed interior hole is free and open to the atmosphere to allow leakage to present itself if it is present. See my video. This is how I diagnosed the check valve in one of these saws. Some do not leak as extremely as this one did, but still need to be replaced.

Pressure testing nozzle/check valve.

 

[lehman live edge slab]

I had a wt 194 that wouldn’t tune at idle, I’d never done check valves in a carb but had some from the old dealership I bought a few things from. After the new check valve carb acted perfectly, id previously rebuilt and cleaned a couple times. The check valve was its last chance of staying out of the trash bin.