Carb High Jet Lean After Rebuild - How to Fix?

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rking453

rking453

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Just rebuilt a WT series Walbro on a Stihl 026. The saw starts and idles great at one turn out on the low jet. When I give it throttle it runs way too lean, two turns out on the high jet before it will stay running, and with the high screw a few more turns out its still really lean. I can't get it to richen up at all. I started thinking air leak, despite it idling well. I swapped an identical carb from my other 026 on the problem saw, and it runs as perfect as you could hope for.

What did I do to mess up this carb?
 
rking453

rking453

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Yes, I made sure everything was ordered the same as I took it apart. When I started having issues I double checked the manual and everything looks the way it should.
1630285092136.png
 
rking453

rking453

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Did you mix up the jets, put the low into the high or the other way around,
some carbs have different angled needles, different diameters, different seats,mixing them up won't help. Is the new diaphram ok, no holes.
I didn't pull them out, the parts I replaced were 2 - 10.

Diaphragm seems good to me. Unless there is a pinhole leak I can't see.

Could there be dirt somewhere blocking flow? If the metering lever is not adjusted right would it cause lean WOT?
 
huskihl

huskihl

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Check to see if the H and L jets might be swapped like mentioned. Also, your metering needle lever may need to be raised a little bit
Nvm, I see you didn’t remove them. I’d tear it apart and spray carburetor cleaner through every orifice if it were me. I’ve seen stuff build up on the end of the jet needles
 
rking453

rking453

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Nvm, I see you didn’t remove them. I’d tear it apart and spray carburetor cleaner through every orifice if it were me. I’ve seen stuff build up on the end of the jet needles
Okay I will give that a try, should I pull the orifice part 13? If so, how do I get it out without damaging?
 
SteveSr

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Did you mix up the jets, put the low into the high or the other way around,
some carbs have different angled needles, different diameters, different seats,mixing them up won't help. Is the new diaphragm ok, no holes.
Most carbs are designed with different size needle threads such that mixing them up is not possible.
 
SteveSr

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Okay I will give that a try, should I pull the orifice part 13? If so, how do I get it out without damaging?
NO, No, No! you are only digging yourself in deeper.

DO NOT use compressed air on a carburetor. Only use spray carb cleaner to clean/verify passages.

If you used the new metering lever in the kit did you set the height? The old one should be reusable and is probably set correctly. The new one MUST be properly adjusted after installation
 
rking453

rking453

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NO, No, No! you are only digging yourself in deeper.

DO NOT use compressed air on a carburetor. Only use spray carb cleaner to clean/verify passages.

If you used the new metering lever in the kit did you set the height? The old one should be reusable and is probably set correctly. The new one MUST be properly adjusted after installation
I used the "W" height adjust tool, I have it so the center peak of the "W" barely presses down the arm. Is this the correct setting? I have never set the height before, just got this info from youtube. Unfortunately I did not measure the height of the old lever before I took it off.
 
SteveSr

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I used the "W" height adjust tool, I have it so the center peak of the "W" barely presses down the arm. Is this the correct setting? I have never set the height before, just got this info from youtube.
If that is a WT series carb look for the WT marking on the gauge and adjust to that.

Unfortunately I did not measure the height of the old lever before I took it off.
You can always put it back in and check.

If that is not it the next step is to remove both needles and shoot carb cleaner through all the passages. I have seen old welch plug sealant get hung up in the needle passages before.
 

J D

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I suspect you have sent some crud into the H circuit when you cleaned it out... Best way is to remove the needles & spray cleaner through them as others have recommended
 
rking453

rking453

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Time to take it back apart… you’ve missed something.

Was the carb / saw acting funny before you replaced the kit?
Saw was very hard starting cold, then ran great once started. Now it starts in a few pulls cold, idles great, i just can't get enough fuel to it at WOT.
 

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