# Saw dies with WOT



## Dswensen (Oct 8, 2006)

I have a Craftsman chain saw (358.350180) I am working on that stumps me. It has a Walbro WT391 carb.

After a good overnight solvent soak for the carb, compressed air blow in all holes, a thin wire to clean all holes, and a carb re-build kit, it starts and idles like a dream (LO screw and idle adjusted). As soon as I add a small amount of throtle, it revs up, a little more throtle and it dies. If I goose if from idle to WOT, it revs for 1/2 second, then dies. It seems to be getting too much gas and flooding out. When I adjust the HI screw, there is no change at all until it is screwed out so far that the saw dies

I have tried many things; I have a Walbro gauge to adjust the metering lever. I have adjusted the metering lever higher, then lower than the gauge tells me. I have tried placing the metering diaphram against the carb body under the thick gasket, then also placing the thick gasket against the body with the diaphram on top (as Walbro says to do). No joy.

Any thoughts would be appreciated.


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## geogrubb (Jul 28, 2006)

My first guess would be a small leak in a fuel line that is sucking air when there is demand for more fuel, second would be to remove the muffler and check for plugged exhaust port and spark arrestor. Have a good one. Geo


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## Dswensen (Oct 8, 2006)

Thanks GEO, but those suggestions did not do it - still same problem. Fuel line was removed and checked for integrity. Muffler is clear. 

If the fuel line into the carb leaked around the connection to the tank (no hole in the line, just leaked around the line) would that affect running characteristics? I get that the fuel would leak, but would letteing air into the tank affect the running of the saw?


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## dawgpile (Apr 28, 2008)

Have you removed the fuel filter from the fuel line in the tank and verified that it's not partially clogged? Air should move freely through the filter when you try and blow/suck through it. Visually it can look perfect but actually be clogged. You can try the saw without the filter attached as long as you ensure the end of the line is submerged in fuel. 

Regarding your question about a leaky connection around the fuel line, it should have no impact on the running of the saw. Just makes a mess as you noted.

Let us know how you make out!


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## hankster (Jan 1, 1998)

I would try opening both the low and high end carb adjustments 1/2 turn and see if that helps. Adjust from there if it does.


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## 30yearTech (Sep 14, 2006)

You may also want to take a look at the cylinder/crankcase mtg screws to see if any of them are loose. They are underneath the saw body and extend up into the cylinder.

Best of luck...


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## Dswensen (Oct 8, 2006)

*Update*

OK, I gave up on the carb, and ordered a new one ($15 delivered). While I was waiting for delivery, I decided to futher disassemble the saw to see if anything else was amiss. Found nothing.

New carb came today - got her all put back together and worked to fire her up.

New problem

Now she'll start with choke, but will die as soon as the choke comes off. As the choke comes off, it will rev slightly and then die.

This sounds to me like an air leak somewhere; the saw seems to be "leaning out" when the choke is disengaged. I've tried various combinations of the HI and LO screws with not much change.

Ideas?


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## geogrubb (Jul 28, 2006)

As per my previous post, replace the fuel lines. Have a good one. Geo


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## Dswensen (Oct 8, 2006)

*Nope, not the fuel lines*

Thanks Geo, but as I said before, the fuel lines are not the problem. I removed them, checked them, and there are no leaks. I had replaced them with "Tygon" lines a few years ago when the DID fall apart.


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## Dswensen (Oct 8, 2006)

*Problem solved*

It was a cracked plastic block between the carb and the cylinder body. The crack didn't open up ( and leak air into the cylinder) until the block was in compression - once disassembled, you could see it unless you were REALLY looking for it. I ordered a new block, but in the meantime - for giggles - I super glued the crack closed, reinstalled, and she runs great. I still beleive that my first problem was a carb problem, but once the new carb was installed, I must have over-tightened the carb and cracked the spacer block.

Hooray - all is better.


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## COMP (Jun 11, 2008)

Dswensen said:


> OK, I gave up on the carb, and ordered a new one ($15 delivered). While I was waiting for delivery, I decided to futher disassemble the saw to see if anything else was amiss. Found nothing.
> 
> New carb came today - got her all put back together and worked to fire her up.
> 
> ...


you got a NEW carb for 15 bucks ?? where ?


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## Dswensen (Oct 8, 2006)

[email protected]

WT391 Carb for $14.94 delivered.

Dan


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