Setting metering lever on Walbro carb

[boraticus]

I'm working on an old Stihl 024AV chainsaw. I've put in a carb kit but I don't have the specs for setting the metering lever. Would anyone know what the clearance is and how to set it without the factory tool? Carb I'm working on is a Walbro WT-110-318.

Any help will be appreciated.

 

[doitmyself]

Boraticus'

It's been many years since my small engine class, but I remember setting those levers. This was some fun detective work....hope it helps.

Two sites I checked (including arboristsite.com) say that the wt lever is set "level to the carb body", so you don't need the Walbro 500-13 tool ($5). Read what they really mean by "carb body"

http://www.rcuniverse.com/forum/m_10422776/printable.htm


BUT....diagrams of the 500-13 tool imply that it is "below" flush: http://www.wind-drifter.com/technical/wg8walbro.php SEE THE LINK to 500-13 pdf TO MAKE YOUR OWN TOOL http://www.wind-drifter.com/technical/WalbroGage.pdf ...this shows .067"

HERE is your answer: THERE SEEM TO BE 2 WT STYLES, ONE IS FLUSH, THE OTHER IS .06-.07 BELOW FLUSH: http://www.lawnsite.com/showthread.php?t=110745 GO TO POST #7 AND CLICK ON THE WALBRO PDF LINK for a picture/description of using an engineers ruler to get the .06-.07 Enlarge the pdf for easier reading.


Other links of interest:

WT manual: http://www.acresinternet.com/cscc.nsf/e7...30?OpenDocument

DIY Guage mentioned above: http://www.wind-drifter.com/technical/WalbroGage.pdf

Walbro factory service manual: http://wem.walbro.com/distributors/servicemanuals/ServiceManual.pdf Slow to load

http://wem.walbro.com/distributors/servicemanuals/HDAseries.pdf

http://tech.flygsw.org/walbro_tuneup.htm

 

[boraticus]

Thank you very much. That info is just what I needed. I spent way too much time searching the web and found everything but that.

I'm having a difficult time keeping the saw running and suspect it has something to do with the metering lever level and your info pretty much proves that right. The lever is much lower than it should be. Going to pull the carb again and adjust accordingly.

Thanks again!

 

[doitmyself]

My pleasure. The confusion between the flush and recessed recommendations was driving me crazy. Finding that link embedded in the lawnsite thread was a lucky find.

Some people print out that tool pdf to correct scale and make their own tool.

I enjoy and learn much from your seat-of-the-pants, experienced based opinions. I don't always agree, but you often bring the side of reality to theory based arguments.

 

[boraticus]

Well, I printed out the file and made myself a measuring tool. Set the lever midway at .065", put everything back together and gave it a shot. Saw fires up but runs out of gas. Pulled the carb again and set the lever even higher to pass more fuel, with the same results.

The carb has fuel in it when I disassemble it but, for some reason, it doesn't seem to feed it to the cylinder. I've had the carb apart numerous times and verified that every orifice and passage is clear. Spark is excellent. I know it's a fuel starvation problem because if I pour a bit of gas into the throat of the carb, the saw will fire up and run until that fuel burns off.

I've had the carb off and cleaned many times with no positive results. I'm beginning to wonder if it's a fuel supply problem? I know the fuel line is passing fuel but I'm wondering if the engine pulse pressure might be weak and cannot drive the fuel pump diaphragm sufficiently to keep adequate fuel in the carb? When the saw fires up it runs for a few seconds on idle and peters out. It will not take throttle. Obviously a fuel issue.

Other things I've checked:

Compression - 125 psi
Fuel pick up in tank - clean
Exhaust port, spark arrester and muffler all clean
Fuel line clear, engine pulse line clear

This is turning into quite a frustrating project. The upside is that I can take the saw apart and put it back together blindfolded!

Will continue to work on it and will advise if I find the cause of the problem.

 

[boraticus]

I pulled the saw apart enough to inspect the pulse line and it's in good shape. I put a cork in the carb boot and blew compressed air through the pulse line. It blew the cork a good 25 feet away. From that, I would assume that the pulse pressure is good. Nonetheless, the saw won't run.

I pulled the carb again and went through every passage and jet. I pulled the mixture screws and blew compressed air through the screw holes blocking the two small holes in the fuel accumulation area near the metering lever to force air through the jets. I also blew compressed air through the two small holes in the fuel accumulation area. Everything is clear. Still, the saw will not run.

If I put my finger over the carb throat and pull the start rope a few times, the carb pulls enough fuel into the venturi to allow the saw to start and run briefly but the carb will not sustain a running engine either idling or at full throttle.

I've tried a number of different settings for the metering lever from low to high with no difference. Fuel gathers in the carb but does not seem to make it through to the jets. Which is strange because if I block the carb throat, fuel will come through the jets into the venturi.

This is the most baffling carb/fuel issue I've come across. Any ideas?

 

[Lt_Oli]

Check the Walbro site for your particular carb, and determine if there is a check valve in the primary metering circuit. This check valve can be jammed by blowing compressed air into the various holes and passages. Try brake cleaner. As a general rule, as you spray the cleaner into one hole, you should see it exit from another.

Replace the fuel lines and impulse line if so equipped. They can become soft overtime and collapse as the saw revs.

When you installed the carb kit, did you replace the gaskets and diaphragms in the correct order? Carb kits work most of the time, but not always. You may need to replace the carb

 

[boraticus]

Originally Posted By: Lt_Oli
Check the Walbro site for your particular carb, and determine if there is a check valve in the primary metering circuit. This check valve can be jammed by blowing compressed air into the various holes and passages. Try brake cleaner. As a general rule, as you spray the cleaner into one hole, you should see it exit from another.

Replace the fuel lines and impulse line if so equipped. They can become soft overtime and collapse as the saw revs.

When you installed the carb kit, did you replace the gaskets and diaphragms in the correct order? Carb kits work most of the time, but not always. You may need to replace the carb


When I spray WD-40 through the mixture screw holes. It comes out in two places. The intake holes in the fuel chamber and the holes in the venturi.

Impulse line and fuel line are both in good shape.

Gaskets installed according to instructions. On the fuel output side, I have the plate, the metering diaphragm then the gasket. On the fuel intake side it's the cover, the gasket then the fuel pump diaphragm.

This is a very perplexing challenge to say the least.

Going to give everything a good once over then probably look for a new carb or just give it up and pick up another inexpensive used saw in good shape.

At the very least, it's been a very good learning experience.