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JohnF2015
JohnF2015, Small Engine Technician
Category: Small Engine
Satisfied Customers: 1072
Experience:  Owner/Service Technician at S & J Small Engines
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I have a echo trimmer. It was bogging down when I would give

Customer Question

I have a echo weed trimmer. It was bogging down when I would give it gas, I changed the fuel with good fresh gas/oil mix, changed fuel line assy with new grommet , lines and filter, installed new plug, and bought a new oem carb and put it on. It ran fine for bout 10 min. Now it will start and idle, but when I throttle up, it's bogging down. I loosened the muffler, thinking it might be spark arrestor , but no change. I'm stumped, can you help me out?
Submitted: 8 months ago.
Category: Small Engine
Expert:  JohnF2015 replied 8 months ago.

Hi, my name is***** will be assisting you.

The first thing that I would try is to adjust the high side carburetor screw out about an 1/8 of a turn which should solve your issue. These carburetors come preset from the factory but are not always exact for every machine and do require a slight adjustment once installed onto your machine. Depending on the carburetor some of the adjustment screws are easily accessible and others you will have to remove a cap or plug before you can get to the screw.

If you can provide the brand and numbers from the carburetor for me I can assist you with the location of the screws.

Thank you it has been a pleasure to assist you.

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Customer: replied 8 months ago.
It's a zama, rb 18 k93 95a, and I don't see adjusting screws
Customer: replied 8 months ago.
I don't think this model has adjusting screws, if it does, don't know where they would be
Expert:  JohnF2015 replied 8 months ago.

I am including a diagram of the carburetor. Take notice of reference numbers 3 and 4. Number 4 is a cap or cover that must be removed in order to get to number 3 which is your adjusting screw.

Expert:  JohnF2015 replied 8 months ago.

Forgot to include the diagram, here it is.

Customer: replied 8 months ago.
Ok, found it, now how do I remove the brass plug to get to screw?
Expert:  JohnF2015 replied 8 months ago.

Most of the time you can use a small flat tip screwdriver and just pop it out.

Customer: replied 8 months ago.
Ok, I just started it, it will idle, I turned screw when throttling up and no change, I turned both ways, and put it back. It idles ok, just won't throttle up
Expert:  JohnF2015 replied 8 months ago.

Does it die when you pull the throttle or just not come up to full rpm?

Customer: replied 8 months ago.
No, when I pull throttle it wants to die, I can take the Choke when I'm holding throttle down ,and move Choke open and closed and make it run fast, but that's only by moving the Choke, as soon as I put Choke off it dies. It won't throttle up with Choke on , just idles, but moving Choke back and forth fast it will throttle up.
Expert:  JohnF2015 replied 8 months ago.

It really sounds like you still have a fuel restriction that just isn't allowing enough fuel to pass through the carburetor in order to keep the machine running at full throttle.

One other thought however would be to check the exhaust screen in the muffler if you haven't already.

Customer: replied 8 months ago.
Yeah I was thinking about fuel restriction too, cause it sure seems that way. I just don't know where to look. It's brand new carb, fuel lines and filter. I already loosened muffler, and doesn't make a difference, does same thing. Scratching my head
Expert:  JohnF2015 replied 8 months ago.

Maybe the pulse hole between the cylinder and the carburetor is blocked which would explain the no fuel problem. You might even check the gasket between the carburetor and isolator flange and the flange and cylinder to make certain that the holes all line up in them.

Customer: replied 8 months ago.
Ok, I will have to check that, when I pulled the carb off and put new one on. Everything seemed ok, but your saying pull the carb mount flange off and check the pulse hole in it and the one going in cylinder?
Expert:  JohnF2015 replied 8 months ago.

Yes, if there happens to be a blockage in that pulse passage it will cause the diaphragms in the carburetor to not operate which in turn will cause no fuel to pass through the carburetor.

Customer: replied 8 months ago.
Ok, will do that in morning. Hopefully that is it.
Expert:  JohnF2015 replied 8 months ago.

Let me know if you need additional assistance with this issue.

Customer: replied 8 months ago.
Ok I will let you know in morning
Expert:  JohnF2015 replied 8 months ago.

I will be watching for your response.

Customer: replied 8 months ago.
Ok, came out this morn and pulled carb back off, I blew air through all ports and holes, put carb back on and started it, it ran good for bout 10 min and it's right back to doing same thing, idles fine, wants to die when you try to throttle up. I turned mixture screw and no change.
Expert:  JohnF2015 replied 8 months ago.

You indicated that you have replaced the fuel lines with new grommet and filter. Did you also replace the white tank vent that goes on the outside which is attached to one of the lines?

Customer: replied 8 months ago.
I put a new one on it
Expert:  JohnF2015 replied 8 months ago.

Let's try removing it and running the machine to see what happens. Since it seems like the machine is loosing fuel and you have done everything else my thought is that it could not be venting properly into the fuel tank which would cause a vacuum inside the tank and no fuel could be sucked out of the tank.

Customer: replied 8 months ago.
Ok, give me a few and I'll try that
Expert:  JohnF2015 replied 8 months ago.

No problem, just let me know what you find.

Customer: replied 8 months ago.
Ok, I pulled off vent and started it, no change, I pulled out fuel filter (which is new) checked all lines and put back together, and still no change.
Expert:  JohnF2015 replied 8 months ago.

So, it still runs about 10 minutes and dies and the plug is dry when trying to restart the machine. It has to be something fuel system related since the plug is dry but everything that you have done up to know should have corrected the problem. I have no other suggestions for you. I am going to opt out of your question which will allow for one of the other experts here to comment on it if anyone has something else to offer you. Thanks