Echo SRM 210 leaking fuel from air filter

[belegedhel]

I have an Echo 210 string trimmer that I recently bought used. The first time I used it, it ran fine, but when I stored it after use (in a perfectly horizontal position), it began dripping fuel from the air filter housing. Every day, it dripped constantly until the fuel tank was emptied out. I tried loosening the cap on the fuel tank,but it made no difference--continued to drip. I suspected that the needle valve was stuck on the Zama carb, so disassembled the carb. Didn't find anything sticky, but the rubber grommet at the tank was cracked, and the fuel lines were going bad, so replaced all of the above, and installed a new carb kit (needle valve, diaphragms, gaskets, etc). Filled it up with gas and fired it up. It started kind of hard int he first place, and didn't run very well. I finally got it to run well with the choke almost completely closed. Finished my yard work, hung it up (horizontal), and sure enough, it began dripping again. Since there is no adjustment on this carb (Zama K75), I'm guessing that I might have an air leak to account for the need to choke it to get it to run. The leaking has me stumped, though.

[bgsengine]

Replace the carburetor - You have a leaking high speed nozzle check valve and they are not replaceable - only way to fix it is a new carburetor. (Echo P/N A021000722 Zama RB-K75)

Also, those Rotary valve carburetors *are* fully adjustable , but they require specialized tools, training, and legally, only shops that have been certified by the particular brand should be doing adjustments on them, as each model may have entirely different adjustment parameters and procedures to keep within EPA Emissions compliance.. However, a new carb is typically pre-set at the factory already "dialed in" for the most part, provided you have no other fuel or air issues, and should not really need any adjustment.

[KE4AVB]

I do agree that carburetor will require replacement for the leakage problem.

But I do differ on the following.

You have a leaking high speed nozzle check valve

Hmmm can you explain how the main nozzle leak if even if the metering valve is closed stopping all fuel flow; unless, the needle or its seat is leaking? I had several of the needle seats that were leaking around the outside of the seats last year. I verify this by pressure testing with the metering diaphragms removed.

As having to run nearly fully choke after a carburetor kit been installed the OP probably didn't set the metering lever to the correct height. Setting or leaving it set too low will cause fuel starvation as it will not pump enough fuel.

[bgsengine]

I do agree that carburetor will require replacement for the leakage problem.

But I do differ on the following.

You have a leaking high speed nozzle check valve

Hmmm can you explain how the main nozzle leak if even if the metering valve is closed stopping all fuel flow; unless, the needle or its seat is leaking? I had several of the needle seats that were leaking around the outside of the seats last year. I verify this by pressure testing with the metering diaphragms removed.

As having to run nearly fully choke after a carburetor kit been installed the OP probably didn't set the metering lever to the correct height. Setting or leaving it set too low will cause fuel starvation as it will not pump enough fuel.

It's an RB carburetor - they have a rather different construction than your usual cube carb fuel flows differently in these. - next time you have one apart, might take a closer look at it.

Also, the other clue is in the rebuild of the carb - if it was disassembled and the rotary valve body removed, it is highly likely they lost the ramp roller and the rotary valve is not opening fully, meaning the main jet needle is not coming out as far as it should, thus, a lean carburetor.. P005001000 roller They are extremely tiny (barely 1mm diameter) and very easy to lose and you'd never know it if you didnt know it was there. easy check to verify that is, turn throttle lever by hand to wide open and make sure the round bore of the valve lines up perfectly with the bore of the carb body.. if it does not, you lost the roller guide. Either case, likely better off with a replacement carb than trying to "fix" this one. But, of course, can always verify it is the metering needle and not the check valve by doing the pressure test as you mention

[Mek-a-nik]

I keep those old carbs just for those #@%&%*!! rollers!

[KE4AVB]

BGS,

I did forget about that small roller that could be lost. I will make a note on my Zama Tech Guide. While at it there is a very thin o-ring in that section too that get lost or damage. It is as far I see in the parts list not available. Until last year when you first mention the roller to me, I had never taken that section part as I seen no need to so. I just let the ultrasonics do their job of cleaning that section.

As for the roller possibly missing as I was informed by you last year it is easily checked for without taking the carburetor back part. As the rotary (throttle) assembly is rotated to max opening it should open the carburetor throat completely if doesn't then the roller would be missing. Example is opening operation would be a ball valve used in plumbing.

I did look over Zama technical guide on the RB and the basic fuel path is still the same, of course it is re-routed due to carburetor design. A primer to pull fuel into the fuel pump diaphragm section. The fuel pump diaphragm pumps the fuel with the help of impulses from the engine. Then the fuel flows on to the needle valve which controls the amount fuel the filling metering chamber. As an impulse from the engine activates the metering diaphragm fuel pressure is applied through the main jet to main nozzle check valve. This nozzle check valve opens under the pressure and supplies fuel. As the fuel pressure returns to zero it closes preventing air from returning to the metering chamber. Any excess pressure on the metering chamber cause by an abnormal leaking needle or seat will cause the main nozzle check valve to open and leak. In that case the main is doing its job as it is design to do.

Technical References: Zama Tech Guide 2007 PDF pages 12-15.

[KE4AVB]

I keep those old carbs just for those #@%&%*!! rollers!

And here I just been tossing the RB's the recycle bin.

[bgsengine]

BGS,

I did forget about that small roller that could be lost. I will make a note on my Zama Tech Guide. While at it there is a very thin o-ring in that section too that get lost or damage. It is as far I see in the parts list not available. .

Echo part number P005000280

[KE4AVB]

BGS,

I did forget about that small roller that could be lost. I will make a note on my Zama Tech Guide. While at it there is a very thin o-ring in that section too that get lost or damage. It is as far I see in the parts list not available. .

Echo part number P005000280

Thanks. I have now have noted in the file.