Walbro HDC experts?

[dswensen]

Working on a middle-aged Homelite with a Walbro HDC carb. Was rebuilding the carb, and damned if I didn't put a hole in the LITTLE screen filter that covers the main nozzle check valve. I'm NOT talking about the filter screen for the metering needle- that one is HUGE in comparision to this little thing.

Anyway, there is a new small filter screen in my rebuild kit, but I'll be dip-switched if I can't get that old TINY retaining ring out in order to get the new screen in. Helpful thoughts on THAT would be appreciated.

I put it all back togther (minus a screen filter for the check valve), and the saw runs good, but a little rich as I expected without a screen over the main jet check valve (there is no "H" adjusting screw)

Other than possible junk getting past the in-tank filter and the metering needle screen to screw up the check valve, is there any other bad thing that happens if I leave this little screen out?

 

[hotshot]

That is actually supposed to work like a one way check valve, using the capillary effect of liquid to seal it off.
It supposeldy seals off the main orifice at idle, but lets the gas mix through at WOT. (You can tell that I am
suspectible about that, but it's detailed in Walbros technical literature...)

Normally, those are a rubber type seal, but then not captured like yours with a snap ring.

I just bent a diaper pin tip over at 90° to slip underneath that tiny snap ring & it works most of the time.
If you try to bend a sewing type needle it just breaks the tip off.

If you need a replacement snap ring & screen, send me PM.

 

[dswensen]

That is actually supposed to work like a one way check valve, using the capillary effect of liquid to seal it off.
It supposeldy seals off the main orifice at idle, but lets the gas mix through at WOT. (You can tell that I am
suspectible about that, but it's detailed in Walbros technical literature...)

I thought so too until I poked that danged hole through the old screening. There appears to be a disk-type float behind the screen that must act as the check valve???

Thank you for your kind offer to help with replacements. If I lose/screw up the ones I have, I'll take you up on it. My snap ring is STUCK.

 

[hotshot]

OK, sounds like the disk will still check the main just fine.

You can still get quite a few of those checks from Walbro or VE Petersen. If you do get a new kit,
you ruin the existing one when you pull it out with a mini slide hammer & screw threaded into the main jet hole.

The Walbro website will provide you with the right kit part number, but the shipping costs as much as the little kit.

What's the carb number?

 

[dswensen]

Took some CAREFUL work, but I got the new screen in and the new snap ring. Back together, fired it up. Runs better now, not so rich. Thanks for the helpful comments!!

 

[redunshee]

Working on a middle-aged Homelite with a Walbro HDC carb. Was rebuilding the carb, and damned if I didn't put a hole in the LITTLE screen filter that covers the main nozzle check valve. I'm NOT talking about the filter screen for the metering needle- that one is HUGE in comparision to this little thing.

Anyway, there is a new small filter screen in my rebuild kit, but I'll be dip-switched if I can't get that old TINY retaining ring out in order to get the new screen in. Helpful thoughts on THAT would be appreciated.

I put it all back togther (minus a screen filter for the check valve), and the saw runs good, but a little rich as I expected without a screen over the main jet check valve (there is no "H" adjusting screw)

Other than possible junk getting past the in-tank filter and the metering needle screen to screw up the check valve, is there any other bad thing that happens if I leave this little screen out?

You have to use a micro screwdriver and carefully pry it out. Same setup on the HDB. Wit a little patience it'll come out.