Carb issues

[hermit_the_grouch]

Hi all,

I've used this forum to fix a few chainsaw issues, first time posting.
I inherited what I believe is a 010 a few years ago. Am I guessing right?

Anyway, it ran great for the first few years after I got it. Only issue was rotting fuel lines, but it ran fine again after a replacement.
Always started easy, etc.
Lately I've had issues keeping it running. It's flooding after it warms up.
Thought it was a carb issue so took it apart, cleaned and did a rebuild, not including stuff behind the welch plug.
It's a Walbro WT-21, and I used the K10-WAT kit from Proline.
Also replaced the tank fuel filter and spark plug with the proper NGK.

Now the only way I can get it to start is close both low/high needles, pull until it de-floods, starts and dies.
Then only open the low speed needle 1/4 turn, and keep closed the high speed.
It will idle fine like that, but obviously won't cut wood.

If I slowly open the high speed I can get it to throttle up, but it starts pushing in so much fuel it dies.
And it continues to push fuel into the carb even after the saw dies, so much it fills the carb throat.
It also seems to be pressurizing the fuel tank. It sprays out fuel when opening the tank. Not real fun.

I would think it's a carb issue, maybe incorrect gasket/diaphragm or inlet needle rocker adjustment or something like that.
But the flooding issue was happening before I rebuilt the carb, so I'm at a loss.

Surely the geniuses here can point me in the right direction?
Thanks in advance for the help!

Jed

 

[pioneerguy600]

Needle seat worn or pitted, possibly varnish or other foreign material stuck on it, needle not sealing completely. Vac test the carb.

 

[Backstage]

Lately I've had issues keeping it running. It's flooding after it warms up.
Thought it was a carb issue so took it apart, cleaned and did a rebuild, not including stuff behind the welch plug.
It's a Walbro WT-21, and I used the K10-WAT kit from Proline.

Check your needle lever height with the Walbro 500-13-1 “W” tool.

 

[rupedoggy]

gasket on wrong side?

 

[AGrig06]

Hi all,

I've used this forum to fix a few chainsaw issues, first time posting.
I inherited what I believe is a 010 a few years ago. Am I guessing right?
View attachment 955560
Anyway, it ran great for the first few years after I got it. Only issue was rotting fuel lines, but it ran fine again after a replacement.
Always started easy, etc.
Lately I've had issues keeping it running. It's flooding after it warms up.
Thought it was a carb issue so took it apart, cleaned and did a rebuild, not including stuff behind the welch plug.
It's a Walbro WT-21, and I used the K10-WAT kit from Proline.
Also replaced the tank fuel filter and spark plug with the proper NGK.

Now the only way I can get it to start is close both low/high needles, pull until it de-floods, starts and dies.
Then only open the low speed needle 1/4 turn, and keep closed the high speed.
It will idle fine like that, but obviously won't cut wood.

If I slowly open the high speed I can get it to throttle up, but it starts pushing in so much fuel it dies.
And it continues to push fuel into the carb even after the saw dies, so much it fills the carb throat.
It also seems to be pressurizing the fuel tank. It sprays out fuel when opening the tank. Not real fun.

I would think it's a carb issue, maybe incorrect gasket/diaphragm or inlet needle rocker adjustment or something like that.
But the flooding issue was happening before I rebuilt the carb, so I'm at a loss.

Surely the geniuses here can point me in the right direction?
Thanks in advance for the help!

Jed

Replace all diaphragms and the needle valve. Might help a bit.

 

[heimannm]

"It's a Walbro WT-21, and I used the K10-WAT kit from Proline."

 

[hermit_the_grouch]

Needle seat worn or pitted, possibly varnish or other foreign material stuck on it, needle not sealing completely. Vac test the carb.

I will take it apart and re-check the seat. How does one vacuum-test the carb?

 

[hermit_the_grouch]

Check your needle lever height with the Walbro 500-13-1 “W” tool.

Wish I had one. I heard you could use a straightedge and left the lever slightly proud above the body

 

[hermit_the_grouch]

gasket on wrong side?

Which one/s is commonly done wrong? I thought I had them right, but I'll check when I take it apart.

 

[hermit_the_grouch]

Replace all diaphragms and the needle valve. Might help a bit.

Yep, did all that with the rebuild kit

 

[pioneerguy600]

I will take it apart and re-check the seat. How does one vacuum-test the carb?

Slip a piece of fuel line on the inlet nipple of the carb, you can suck enough vac with your mouth to tell if it won`t hold vac. I use one of my MightyVac tools most times as I want to test for pressure as well, called a pop off test. For a quick test I have likely used mouth suction more times than the vac tools.

 

[hermit_the_grouch]

Check your needle lever height with the Walbro 500-13-1 “W” tool.

After further review of the W tool and some YT videos, I think the lever must be way off. Do you happen to know the height offset of the middle W point for a WT? It looks like 1/8" or so.

 

[hermit_the_grouch]

Slip a piece of fuel line on the inlet nipple of the carb, you can suck enough vac with your mouth to tell if it won`t hold vac. I use one of my MightyVac tools most times as I want to test for pressure as well, called a pop off test. For a quick test I have likely used mouth suction more times than the vac tools.

Perfect, thanks for that. I'll check it out. If it doesn't hold vacuum, what does that mean, that the needle/seat is bad?
Thought I read somewhere that sucking gas through a tube is only for those with a "strange palate"

 

[pioneerguy600]

Perfect, thanks for that. I'll check it out. If it doesn't hold vacuum, what does that mean, that the needle/seat is bad?
Thought I read somewhere that sucking gas through a tube is only for those with a "strange palate"

Don`t have gas in them when I rebuild them. If it won`t hold vac then the needle valve is not sealing for some reason, gave several reasons in my first post. I have found all the reasons I gave on problematic saw carbs . I have rebuilt or rectified.

 

[Backstage]

After further review of the W tool and some YT videos, I think the lever must be way off. Do you happen to know the height offset of the middle W point for a WT? It looks like 1/8" or so.

That could do it!

The tool is like $10 for both the Walbro and the Zama version and not hard to source.

If you’re in a time crunch and don’t have one yet, the WT carbs are marked on my tool to put needle lever height about 0.065” or 1.6mm BELOW your straightedge across the carb face.

 

[Backstage]

Which one/s is commonly done wrong? I thought I had them right, but I'll check when I take it apart.

In order from metering to pump it’s usually:


METERING SIDE:

Screws
Metering Cover
Diaphram
Gasket
***CARB BODY***
Pump Valve Insert Thingie
Pump Valve Gasket
Pump Cover

PUMP SIDE

When you’re taking apart something you’re not completely familiar with, always take pictures.

 

[Backstage]

Slip a piece of fuel line on the inlet nipple of the carb, you can suck enough vac with your mouth to tell if it won`t hold vac. I use one of my MightyVac tools most times as I want to test for pressure as well, called a pop off test. For a quick test I have likely used mouth suction more times than the vac tools.

In absence of a vac/pressure tool, my preference is a known good purge bulb, but everybody has their flavor preferences… lol

 

[pioneerguy600]

In absence of a vac/pressure tool, my preference is a known good purge bulb, but everybody has their flavor preferences… lol

I have even used various ,syringes with a length of hose, often have one or more on the bench or tool trays.

 

[Captain Bruce]

Hi all,

I've used this forum to fix a few chainsaw issues, first time posting.
I inherited what I believe is a 010 a few years ago. Am I guessing right?
View attachment 955560
Anyway, it ran great for the first few years after I got it. Only issue was rotting fuel lines, but it ran fine again after a replacement.
Always started easy, etc.
Lately I've had issues keeping it running. It's flooding after it warms up.
Thought it was a carb issue so took it apart, cleaned and did a rebuild, not including stuff behind the welch plug.
It's a Walbro WT-21, and I used the K10-WAT kit from Proline.
Also replaced the tank fuel filter and spark plug with the proper NGK.

Now the only way I can get it to start is close both low/high needles, pull until it de-floods, starts and dies.
Then only open the low speed needle 1/4 turn, and keep closed the high speed.
It will idle fine like that, but obviously won't cut wood.

If I slowly open the high speed I can get it to throttle up, but it starts pushing in so much fuel it dies.
And it continues to push fuel into the carb even after the saw dies, so much it fills the carb throat.
It also seems to be pressurizing the fuel tank. It sprays out fuel when opening the tank. Not real fun.

I would think it's a carb issue, maybe incorrect gasket/diaphragm or inlet needle rocker adjustment or something like that.
But the flooding issue was happening before I rebuilt the carb, so I'm at a loss.

Surely the geniuses here can point me in the right direction?
Thanks in advance for the help!

Jed

Replace the carb with a NIB unit. For 20 bucks, you may solve your issue within 20 mins. IF not, send it back and completly go thru the existing. Somehow, this shouldn't turn into a 10 page thread.

 

[hermit_the_grouch]

I took it apart again and double-checked everything. It did hold vacuum.
In the rebuild kit there was a gasket that looks like rubberized fiber mesh (similar to old one) with little flaps on it, and an identical shaped gasket of very thin black plastic (not on old one). I had put both on, and had heard you can leave them together to boost fuel pressure, but figured I should take one out.
I removed the fiber mesh one and left the plastic one in.
Adjusted the metering lever to what I guessed was the right level. Really need to buy one of those W tools.
Put it all back together and after a little L/H needle adjustment, she runs again, no flooding!

Thanks to all responders for the help!