Need troubleshooting help on Poulan Pro 46/18 (fuel system)

[fearofpavement]

I usually only work on saws I own. That said, a friend of mine from church has been having problems with his PP 46cc.
I checked it over, pulled the muffler and the screen is clear, the piston looks new and the compression seems stout.
Symptoms: The saw will start but essentially revs up, leans out and quits. (repeat, repeat, repeat.)
It seems to be starving for fuel. This one doesn't have a primer bulb, just a single fuel line from the filter to the carb. I confirmed the integrity of that line. I pulled the carb apart. It seemed pretty clean and the diaphragms all looked fine. I changed one gasket on the metering side. I put it all back together but what a pain trying to get half a dozen pieces in the handle all together. I would never keep one of these as a personal saw as I was very unimpressed with the complexity of the assembly related to all the layers of stuff and twisted cables and so forth that all have to be squared away.
Long story short, I got it all back together but it essentially runs the same way.

Here's some additional info:
1. The carb screws were both about 2.5 turns out. That seemed like a lot so I set them at 1.5 for initial. I haven't tried opening up the H more to see if that would help. The saw is still leaning out and quitting.
2. I didn't pay as much attention to the L and H screws as I should have and not sure I got them back in the correct hole. They both have the same thread, are the same length but one has a little bit different taper on the point so they need to be in the correct hole. One of the screws has a radial groove in the head. I put that into the H side.
3. I looked at the induction mounting area and boot the best I could but it's not really visible. No rubber parts on this saw were hard or cracked so I don't suspect a torn boot but...
4. I drained the tank, checked the filter and refilled with clean gas. The fuel was clean unlike the water filled fuel I drained out of my new to me MS460.

I quit for today as I feel like crap but can still type.

What do I need to check next?

 

[HarleyT]

When you get the carb off again, and dis-assembled. take off the needle/lever/spring, and hold the carb up to a light, you will likely find the passage under the needle mostly clogged, blow it out, and visually verify that the passage is clear, and re-assemble....

 

[nenicu]

Same problem today with a Ryiobi 44 cc[Redmax 4500]. Zama C10 carb. The saw starts ,idles , it dies when trying to rev. The fix: i set the metering lever up a bit.

 

[fearofpavement]

I went through the carb. There are no apparent restrictions. The hole is clear, I removed the screen (it was clean) The saw had been running so not likely the metering height changed and it looked fine. I'm just not sure where to go next. I don't plan to go back into the carb, I'm done with that.

Anyone here can confirm I put the screws in the right holes?

 

[HarleyT]

You didn't look through the hole then.

 

[nenicu]

PS. I used compressed air to clean the h needle hole the second time i cleaned the carb. The first time i just used carb cleaner.

 

[Chris-PA]

If it ran a little longer I'd suspect a clogged tank vent, but not if it quits that quickly.

You do not need to disassemble the handle to take the carb off - the cable and filter support get in the way a bit but not too bad. The carb support is attached by two screws down onto the case (under the carb). Yours should look like the one on the right:



There could be a tear or defect. If you look at the second picture you can see that the rubber can get distorted over by that slot/impulse passage. There is a plate that sits over this:

It's quite possible for leaks to occur there, in either the intake or the impulse, or between them.

 

[o8f150]

when I get one in the shop the first thing I do is fuel lines and carb kit after I check everything else,,, problem is solved,,, 99% of the time it will take care of the problem

 

[fearofpavement]

You didn't look through the hole then.

Yes I looked through the hole. How many ways can I explain it? The hole is clear. This isn't my first rodeo on a carb (or 50th)

 

[fearofpavement]

when I get one in the shop the first thing I do is fuel lines and carb kit after I check everything else,,, problem is solved,,, 99% of the time it will take care of the problem

Those were the first things I checked.

 

[o8f150]

Those were the first things I checked.

there has been several times the diaphrams looked good but still ran that way,,, I just went ahead and put a kit in and it ran fine after that,,, why I don't know since the diaphrams wasn't bent or torn,, guess they where just to stiff,,, after 2 hours of banging my head against the wall I learned so after that they always got at least a carb kit if they showed those sytems

 

[HarleyT]

Well, your insisting on not going back into the carb really puts a chitmist on you getting this saw to run then, as that is pretty much what you need to do......

 

[fearofpavement]

Harley, what do you think is wrong with the carb?

 

[HarleyT]

Well it sure sounds like it has a clog in there somewhere, you are seeking a response that will not involve going back into the carb,
well I am sure some folks here will come up with something.... Hell, turn both mix screws out an extra turn, and see what happens, it will likely do a lot better. Not right, but at least better.

 

[fearofpavement]

I'll try opening the screws some more and see what happens. Can anyone confirm if the grooved screw is for the H side or L side?

 

[HarleyT]

I never take them out, what model/brand carb is it? Have you tried swapping them?

 

[Chris-PA]

Can anyone confirm if the grooved screw is for the H side or L side?

I wish I could, but I don't recall seeing such a groove. I believe it's a WT (unless it's a ZAMA?), and I didn't think the screws were really different but I'm not certain.

If it's a WT, let me know the model number and I'll see if I have one that has not been violated yet.

 

[fearofpavement]

It's in the Walbro 20 family. I too thought the screws were identical and it wasn't until detailed examination that I noticed very minor differences. The groove is on the splined portion of the screw near the screwdriver end. I've been searching around on the web and haven't found anything definitive. I very well may have a similar saw carb and can answer my question but that's going to have to wait until I get feeling better.

 

[Modifiedmark]

Let me get this understood. You say you suspect its starving for fuel so you close both mixture screws in another turn?

Uh, Ok.,

In case you didn't know it a lot of these newer Walbro cars don't do that 1 turn out anymore and need to be opened 3-4 times that.

A good thing about these are you can buy new carbs from Poulan for less then $20 and there pretty much set right out of the box..

 

[fearofpavement]

Opening the screws up (a lot) is next on the list).