Echo Backpack - Pulling my hair out!!!

double_o_zedNovember 22, 2010

So, I have an Echo PB-403T which ran great for the past few years. Lately it has been bogging out at about half throttle and spitting gas out of the carb. Blowing leaved at that speed just isn't fun, so I removed, thoroughly cleaned and rebuilt the carb with a Zama rebuild kit. put it all back together and it's still doing the same thing. It's spitting gas back out the air filter. Doesn't matter how I adjust the high speed screw, it still blows back gas out of the carb.

Does the PB-403T have a reed valve on the intake? Am I missing something? I'm pulling my hair out on this one.

Thanks for your help. WB2GLP

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D: A rebuild kit will do nothing to restore fuel response on a partially restricted High speed circuit. Get some concentrated fuel cleaner and spray the high speed jet circuit and low speed while your at it . Replace the fuel with fresh mix and additional 2 ounces of carb cleaner at let it sit for 20 minutes . Start the Blower and keep it running until the cleaner begins to remove the gum and residue within the system . Normally 1/2 tank does the job extremely well . Next time ensure to put Stabil while storing and Lucas Top end cleaner / lube during seasonal start up Tank .

    Bookmark   November 22, 2010 at 5:08PM
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A clog muffler will also cause gas to blow back through the carb.Take the muffler off and check the spark arrester screen in the muffler.Hope this helps.


    Bookmark   November 22, 2010 at 5:21PM
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I will check the exhaust for blockage which makes sense knowing it runs, but spits fuel out the carb on acceleration.

I had the carb completely apart on rebuild and it spent a few minutes in my ultrasonic parts cleaner. I don't think deposits are the problem, but I will definitely look in that direction next.

If I can't figure it out, it's going on ebay for parts.


    Bookmark   November 23, 2010 at 10:39AM
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I rather doubt the problem is a carbon deposit issue within the exhaust system causing excessive back pressure. I have Serviced and Tuned 1/2 dozen Echo's within the last few yrs and only one had excessive carbon fouling accumulation issues. In that case (Gas Trimmer)the owner had mistakenly doubled the recommended 50-1 Fuel/Oil Ratio and had compounded it with using a cheap variety store multi use 2-stroke oil . Never hurts to check your exhaust (muffler) but Echo mufflers can be easily damaged . I would simply check the spark plug and piston dome for evidence of excessive oily carbon particulate. I have serviced numerous Echo Saws and not one has shown evidence of any carbon fouling but then the Epa has pretty well looked after that within the last few yrs on the Professional Saw Market lol . If the unit has been used buy others and is older than your 2 yr scenario , then by all means the service and operating criteria could be suspect . As for ultrasonic cleaners they take much more than a few minutes to effectively remove any particulate or residual build up within a 2-stroke carb. However you are on the right track and have done most everything than ensure a new plug and properly tune the unit. I suspect you have cap limiters so there is not much tuning really required . Best of luck let us know how it goes Bro :)

    Bookmark   November 23, 2010 at 1:07PM
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strelnikov(NE IL)

The spark arrester screen on my Echo string trimmer was plugged up once. It sputtered a bit on the first couple of pulls but wouldn't run at all until I removed the spark arrester screen. After that it started and ran fine. Of course I tried fixing everything else first.

    Bookmark   November 25, 2010 at 3:28PM
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