Walbro HDA Testing Question

[mdep]

I am installing a K22-HDA kit in my Husky 350 and it does hold pressure and there are no leaks but the the idle needle does not pop-off under pressure. I put 30+ PSI in and no pop-off. Is the Walbro HDA-159A supposed to pop off. I did it dry and with mix in the line.
A slight press on the needle are and the needle opens. In fact, I can blow lightly in the hole of the metering chamber cover and the needle unseats.
Do I need to take the butterflys apart? Is there a inlet check valve that would be causing this and if so where is it?
Also, the K22-HDA repair kit had a tiny screen and a semi-circle metal clip. Where to they go?

Thanks for any help you can provide.

 

[HarleyT]

Nah. Take it back apart and make sure the passage under the needle is clear, and make sure the lever height is correct,
a good sealing needle is not a bad thing

 

[mdep]

Without the inlet needle installed I get fuel spurting out the seat when I pump fuel in the carb inlet. When I shine a light from the pump side of the card threw where the screen filter goes, I see light when looking at the the inlet needle seat. That should show that it is not blocked, shouldn't it?

 

[HarleyT]

Well, if it looks clear...
If is doesn't show a nice clear passage....

well then you need to blow it out...

 

[HarleyT]

Spurting doesn't tell much....

Well...... Not for us old dogs....

 

[mdep]

Been soaking, spraying and blowing out a bunch. Pump diaphragm against the carb then the gasket and cover. On metering side it gasket against the carb, then the diaphragm and cover. Needle lever is even with carb surface. First one I've ever done so..

 

[drf255]

I thought HDA covers didn’t have a metering cover hole? Don’t they have that internal passage that required a special metering gasket and diaphragm with an extra vent hole?

As said, make sure metering lever height is correct. Also, if you have another spring, swap it in and see if popoff changes. Makes sure that the needle is the length of the old one. I’ve seen tiny variations in carb kits and it will make a difference.

I’ve had more carbs messed up by lowering popoff than by leaving them at 30+. Just the way it goes. When it pops off, where does it reseat?

 

[albert]

Only some. Only seen theem on sweds 199 ect. Their version of intelicarb.

 

[mdep]

I never got it to pop off so don't know the reseat pressure. My MityVac only goes to 30 PSI them some unkown amount above the labeled range. I went into the scary unknown! Maybe I could try using my compressor and adjusting the output pressure from 30 psi up until it pops off, if I could pinch off the pressure in the line once it pops off.

On one video I watched, the pop off test was done with the metering side opened. You could then see the needle pop off action. So for the pop off test itself, it doesn't really matter what the height of the needle lever is.

I read that the higher or lower pop off would make the engine run leaner or richer, respectively, throughout the range of throttle. With the reseat pressure being even more important. Is there any way the spring could have gotten stiffer? I don't remember if the dealer ever had the carb opened.

I'll check the size of the needles. Looked the same but I do have questionable vision.

 

[mdep]

The needles look the same size. Needle would not pop off with either of them. With just the needle and no spring or lever, the needle pops off with omly slight pressure. I pulled a very thin vinyl straw from a broom and could push it from the pump side to the underside of the needle and easily make the needle open. The hole looks clear between each side, as shown in the photos.



However, if I look with my eye right up to the hole, I believe I see a translucent film across the hole. That film has a little hole in it. Unless that's a filter/screen, it must be some kind of solidified gum. Is there supposed to be a screen there? If it's gum, what would dissolve it quick. Can I knock that seat out from the other side?

Here's some photos of the carb and diaphragms/gaskets. Inlet screen and plug removed:


Some of the old and new parts:

I don't know where the brass cap, c-ring and tiny screen goes?


Thanks for any answers to questions you can provide.

 

[HarleyT]

Kits will cover many possible model carbs..

 

[HarleyT]

You are the first poster to post a pic of his nice clean hole!!!

 

[HarleyT]

Get rid of it.

However, if I look with my eye right up to the hole, I believe I see a translucent film across the hole. That film has a little hole in it. Unless that's a filter/screen, it must be some kind of solidified gum. Is there supposed to be a screen there? If it's gum, what would dissolve it quick. Can I knock that seat out from the other side?

 

[HarleyT]

here is where the lever height should be.

 

[Huskitoter]

Been soaking, spraying and blowing out a bunch. Pump diaphragm against the carb then the gasket and cover. On metering side it gasket against the carb, then the diaphragm and cover. Needle lever is even with carb surface. First one I've ever done so..

Link is to a diagram if needed. When they say level on lever adjustment, that means just under level.

https://www.partstree.com/parts/hus...-husqvarna-chainsaw-1998-02/carburetor-parts/

HarleyT may have some good advice above. It may be time to move on to plan B if you can't get it to work. No problems with the el32 in my later 350.

 

[cuinrearview]

Maybe I missed it in one of the threads about this, but did you put it back on the saw and try and run it yet? I've re-built a couple 159s lately and threw them back on the saw. And it runs fine

 

[rmh3481]

Some of the HDA's have a screen check valve and others have a nozzle on the H side. Which H circuit does your carb use? The small brass plug in the floor of the metering chamber is the access to the H circuit check valve system. Dont open it unless you have an old carb to practice on first. Same thing with the welsh plug that covers the L circuit fuel feed. Any leaks in those plugs are trouble.

Also pay attention to the order of the gaskets and diaphragms because they are reversed from side to side. Metering side - 4 screws side, gasket goes down against the casting first followed by the diaphragm and then the cover. Pump side - the diaphragm goes down first and then the gasket followed by the cover.

 

[mdep]

I am all good on the assembly. Did refer to the diagram to make sure. Metering lever is up to but not moved by a straight edge. I replaced the inlet screen and the welch plug after I removed them for cleaning. Did not touch any of the brass stuff. Except I cleaned the needle seat. I don't know anything about the check valves or H circuit, yet.

The only problem I had was with the pop off. It would not pop within the range of the MityVac (30 PSI). A Walbro tech told me they don't specify pop off pressure because of the differences in the springs. He said you can manually pop it and the reseat pressure must be at least 5 psi. I used my compressor to get an idea where the needle would pop off and was at around 95 PSI.

So I ordered a new Walbro spring. The I removed some of the spring I have. Ended up taking off three springs turns. Now it pops off at around 20 and reseats at 7. We'll see what the new spring does.

In the mean time I put the saw back together and added fuel and oil. The saw ignited after about 5 pulls with choke and started in a couple pulls no choke. Ran a few secs. I was in the basement. Threw out a bunch of smoke. Will try outside tomorrow. Right now the saw is sitting in a plastic tub just in case the oil and fuel leaks are not fixed.

I'll try to tune the carb tomorrow starting at 1 turn out on the H and L I guess. How about the T?

Will update when I get the new spring in and try that. Then I'll revert back to my original thread on the Husky 350.

 

[Huskitoter]

Nice. Doing that testing with the vac is cool. Most just stick them on the saw and see if it works.

There is no default position for the idle screw. You have to adjust it after adjusting the low mixture. Turn it in if the saw dies before or while adjusting the low if needed.

 

[redunshee]

I've never done a popoff test. Think ur problem is elsewhere.