2 stroke carb question

Let me start by saying that 2 stroke carbs are my nemesis, I hate working on them. When I'm asked to look at one for a friend I usually end up recommending replacement right off the bat.

I have an Echo PB-2100 leaf blower that I've had for a LONG time, she's been good to me.
It was running rough so I took the carb apart, completely apart and went through it about three times. I replaced the diaphragm. It starts right up now and runs strong....as long as I'm pointing it at the sky! When I lower it the engine will bog down and choke out. If I point it up it runs strong again. Can anyone tell me what I did wrong?

The fuel lines are in very good condition, replaced not long ago. It has a new fuel filter and spark plug. I've blown air into the lines to see if the lines were cracked or had a pin hole but found no leaks.

Are you sure the fuel supply tube with the filter is staying submerged in the tank as you shift the blower about? Or venting perhaps. With enough fuel to run but not spill out, try loosening the fuel cap as you begin to lower the blower and see if it'll stay running.

I'll check those things and let you know, thanks Logan!

Another possibility is that you have the fuel lines reversed. If the lines were in fact reversed it would make it so the fuel level would cover the shorter return line (which is connected to inlet) when pointed up and provide fuel to the carburetor but not when pointed down. Double check your fuel line connections. If the carburetor has a barbed fitting it should be connected to the fuel supply line.

I'll double check that as well. Thanks!

arch252 said:

Let me start by saying that 2 stroke carbs are my nemesis, I hate working on them. When I'm asked to look at one for a friend I usually end up recommending replacement right off the bat.

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I'm with you on that, rebuilding them is hit or miss.

Logan, I checked the position of the fuel filter and it moves about freely in the tank. I checked to see if the lines were reversed but they were not, they were correct. Any other ideas?

Dealing with these on a daily basis I have a few diagnostic tools that you may not.
however with a diaphram carb that is sensative to engine orientation it can only be a few things.
1) cracked , stiff or incorrectly fitted diaphram
2) inlet pipe & return pipe connected back to front
3) crack in fuel inlet tube / partially blocked fuel filter .

Double check the connections.
The tube nearest the primer bulb is the return and goes to the tube that ends just inside the fuel tank, not the supply tube with the fuel filter on.
The primer BLOWS air back into the tank which draws fuel into the other tube.

I have an alternate fuel tank with a known good fuel line that I hook up to the suspect tool.
Problem gone = new fuel line & filter.
The fuel line oft splits near the fuel tank grommet so the carb sucks air when ever that section of tube is above the fuel level.
Similarly with the fuel filter, the bottom gets gummed up so only draws fuel when the upper sections are below the fuel level.

Awesome, thanks Bert. I'll double check the diaphragm to make sure it's oriented correctly and check the lines for cracks.

I did an overhaul on the carb tonight. I had a spare matching carb body that I knew was in good shape so I cleaned it again and swapped it out. I put in another new diaphragm and both gaskets. I replaced the fuel lines. I started it up and again it ran strong at first but quickly started to choke out. When I pointed it up in the air it would run good again. So based on that I'm confident this is not a carb issue.

I'm guessing now that perhaps the rubber grommet that the fuel lines pass though is not sealing well. When I tilt the blower up the grommet is submerged in fuel and that's when it runs smooth. When I lower it the grommet is exposed to air inside the tank. I haven's seen any fuel leaking from the grommet but I can't imagine what else it could be. I have replaced that once before. It's a three hose grommet with the third hose going to what I guess is an air check valve. I'm going to replace that and see what happens. It looks in good shape though.

Side note...when I was cleaning out this second carb body I blew out the small screen on the flip side of the needle valve. I was going to replace it with a spare I had but I forgot. If I leave it out am I asking for trouble or would it be alright to run it without it. I've pulled that carb apart about a dozen times now and I'd really like to avoid doing it again if possible. I'm pretty cautious about clean fuel and I've never seen a dirty screen in any of my equipment. I was going to leave it and if the carb fouled up because of it I would just pull it off and clean it then, hopefully a long time from now. Am I crazy for even thinking that?