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#608028 - 05/25/10 10:02 AM WT-669 Walbro continued problems> Weedeater carb
mahatma Offline
newbie

Registered: 05/22/10
Posts: 6
Loc: Panhandle of Texas USA
Continued from this URL
Walbro Carb WT-669
I wrote this to JasonB after reading the above post. I am still having problems with this Walbro card.

I saw your post on setting the high and low side of this carb. This thing is driving me nuts. I pulled the fuel lines from it last winter and found that was NOT the thing to do. This summer it would never prime right and wanted to run on choke only. Well I rebuilt the carb, made sure the exhaust was not plugged and started again. Like at the start however it only seems to want to prime if I point the weedeater straight up. Once primed it seems to stay in fuel. The in tank filter seems to be fine. The lines look good. So I ground around the adjustment screws and tried what you said. About 1.5 to 2 out it will start full choked but only idle for about 25 seconds. I have tried to fine adjustment in that range but can never get any better than that. This is all with new fuel I forgot to add. I saw someone say they pulled the adjustment screws completely out and cleaned the ports. Does that need to be done. That is the only thing I have
not done that I can think of.
JKH

Here were a few suggestions from JasonB to catch us up. That I might have possibly swapped the lines to the carb. They are different size. The small tube is the incoming fuel line that is tied to the filter. The larger line has no line in the tank and just ends were it enters the tank. As you prime it cycles gas from the tank through the carb pushing the air out the larger line.

He also wondered if maybe the incoming line might have a hole in it. I did too. Once the carb is primed I never see air in that line. Also when I prime into that like it blows bubbles out the filter only. It does act like the old 6lb pressure fuel pump on a old chevy sucking air through a bad fuel line but I dont think that is it.




Edited by mahatma (05/25/10 10:57 AM)

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#608029 - 05/25/10 10:56 AM Re: WT-669 Walbro continued problems> Weedeater carb [Re: mahatma]
JasonB Offline
Sharp -Shooter
Carpal Tunnel

Registered: 04/27/04
Posts: 14066
Loc: Cape Spencer, New Brunswick, C...
Mahatma,

Thanks for moving this into the open...

The priming problem sounds like there may be an air leak in the fuel pick-up tubing.... since you can only prime it when it's standing up... I might suggest that replacing the fuel supply line from the in-tank filter all the way to the carb would be a good idea. A pinhole will have you chasing a tune for a LONG time!

I'd like to know what you did when you rebuilt the carb... Did you simply install a carb kit? An engine that will run only on choke may well have the carb internals gummed up pretty badly. Care must be taken to clean'em out very carefully. Usually a cleaner of some sort (carb cleaner, with care, brake cleaner, white vinegar can all work) is used to dissolve the varnish. A carb cannot be completely cleaned without removing the Hi and Lo needles... Their seats are a prime varnish location.

Did you install a new carb kit? If the metering diaphragm (the big one with the metal plate in it) gets stiff, tuning is hopeless.

How did this machine come to be a poor runner? Did it quit in use, or did it not run right out of off season storage? This could give us a clue as to how it came to fail. If it quit in-use, checking the cylinder's condition would be warranted... Easy to do... Remove the sparkplug and muffler.... Cylinder should be clean and shiny... And the piston should be too (with some light carbon on the crown).

1.5 turns out for Hi and Lo mixtures is usually an appropriate place to start. Some newer carbs have much finer threads on the screws and may need to be several turns out, but generally that's not the case except in the newest emissions engines. It's always best to check and note the settings that last worked... Any chance you noticed this when re-setting the needles? They're often finalized in the 3/4 turns out range...

Stick 'round and we'll have'er running.

J
_________________________
er, somethin'....

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#608030 - 05/25/10 11:11 AM Re: WT-669 Walbro continued problems> Weedeater carb [Re: JasonB]
mahatma Offline
newbie

Registered: 05/22/10
Posts: 6
Loc: Panhandle of Texas USA
Quote:

The priming problem sounds like there may be an air leak in the fuel pick-up tubing



I will replace that first and see how we do.
Quote:

I'd like to know what you did when you rebuilt the carb... Did you simply install a carb kit?



No I took chemtool to it. I squirted out every hole then placed it in a rag and let it dry. I DID not remove the hi and lo needles however.

Quote:

Did you install a new carb kit? If the metering diaphragm (the big one with the metal plate in it) gets stiff, tuning is hopeless.




Yes the complete one with the needle seat.

Quote:

How did this machine come to be a poor runner?



At the end of last season I pulled the fuel lines from it and ran it out of fuel. I have since learned that does no good. Since I have started on it this year it has had the strange priming problem and has always wanted to run with some of the choke enabled.
Quote:

Any chance you noticed this when re-setting the needles? They're often finalized in the 3/4 turns out range




The needles seemed to be out about 1 turn out. Now when I can get it to do its short idle I have them probably a 1/8 to a 1/4 more out.

Thanks
JKH

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#608031 - 05/25/10 11:21 AM Re: WT-669 Walbro continued problems> Weedeater carb [Re: mahatma]
JasonB Offline
Sharp -Shooter
Carpal Tunnel

Registered: 04/27/04
Posts: 14066
Loc: Cape Spencer, New Brunswick, C...
Really screams of either clogged jet or air leak in the fuel inlet tubing to me...

Once things are "right" again, the carb tuning should end up close to where it used to be...

Not that this helps right now, but here's what I do for avoiding storage related troubles like this:

1. I always run stabilizer in all my gasoline. I only keep a gallon or so at any one time, so it's always fresh. If the gas is always stabilized, and you have to leave some in the equipment due to unforseen circumstances, it's not likely to go bad and cause troubles.

2. When I am planning to store equipment, I try to be about out of gas after the last use. Drain what's left in the tank, and burn the carb empty. Use choke at the end until it won't even "pop" to be sure it's all out.

or

Fill the tank to the brim with stabilized fuel (double the stabilizer dose).... This is less sure, and I've had some minor difficulties, but not to "carb-rebuild" bad.

Good luck,

J
_________________________
er, somethin'....

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#608032 - 05/25/10 03:35 PM Re: WT-669 Walbro continued problems> Weedeater carb [Re: JasonB]
mahatma Offline
newbie

Registered: 05/22/10
Posts: 6
Loc: Panhandle of Texas USA
Looking at these diagrams WT-669 I can not tell exactly what is supposed to close and open during the prime process. I know when you press the bubble down it blows air out the inlet fuel line. But I don't get any resistance as the bubble fills again. It sounds as if it is sucking air from somewhere but I cant tell where. Shouldn't it also be applying a force as it fills again? I changed the fuel lines and cleaned the needle valves. I can get it to start but not run.

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#608033 - 05/29/10 09:16 AM Re: WT-669 Walbro continued problems> Weedeater carb [Re: mahatma]
mahatma Offline
newbie

Registered: 05/22/10
Posts: 6
Loc: Panhandle of Texas USA
OK guys I fixed this. After tearing it down 15 times I had about given up. The place it was sucking air from was the check valves and the return fuel line. Return fuel line was off inside the tank. That is why the thing would work if I pointed it straight up in the air. It submersed the return fuel pipe. Sounds simple enough doesn't it!

Here is another great link to Walbro working theory. Walbro theory


Edited by mahatma (05/29/10 09:18 AM)

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#608034 - 07/26/10 09:40 PM Re: WT-669 Walbro continued problems> Weedeater carb [Re: mahatma]
Foreverwood Offline
journeyman

Registered: 07/19/10
Posts: 59
Loc: Florida,USA
Must have been the filter line in the air. The return line in the tank brings gas into the tank, not the carb.

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