Echo backback blower dies as RPMs increase

[Skier76]

I've got a Echo PB500H backback blower that I've had for about three years. I've never had any trouble with it. Lately, I noticed it wasn't reving up to full throttle. More recently, anything over 1/3-1/2 throttle and it dies out.

Today, I replaced the following with an Echo OEM kit: Air filter, fuel filter, and a correctly gapped plug. I also pulled the exhaust screen out and inspected that. Nothing seemed to work; same problem: It dies over 1/2 throttle.For the record, the old fuel filter was clean, the air filter wasn't that bad and the spark plug looked fairly good. Replaced em all anyways. Running the unit sans the air filter still results in the stall out.

I'm using the same gas/oil mix in my trimmer and that has no issues.

Any ideas on where to go next?Fuel line? Primer bulb?

 

[pen]

Have you tried giving it a bit of choke or a partial push of the primer bulb at the same time you are asking it to rev up? Doing that can help you see if it's starving for fuel at that point or not. If a little wiggle of the primer bulb or a touch of choke lets it rev up, you know you have a restriction somewhere that's making you lean out a WOT.

Does the problem happen right from the start of the unit? Or does it operate properly for a while, then get worse as the unit warms up?

With a unit this young, I'm guessing it's a fuel issue rather than a spark issue.

pen

 

[MasterMech]

Sounds like the high speed circuit in the carb is plugged/restricted or it just can't pump enough fuel to keep up. Could have a stretched or torn diaphram in the carb causing metering issues or a leaking fuel line causing it to suck air. I'd start by checking out the fuel line then move to cleaning out the carb thoroughly and replacing the diaphrams/gaskets.

 

[Skier76]

pen,
The choke makes no difference. It'll actually stall out a bit faster. However, I can try again tonight. The problem happens when the unit is cold and warmed up.

MasterMech,
The fuel lines "look" good to me, then again, I suppose it could be a very small crack somewhere. There's no leaking or seepage from the lines or the bulb.

Page 6 here: http://www.echo-usa.com/getattachme...-b956-1d3c903ced31/PB500Hes_P02311_081012.pdf shows the exploded view of the carb. Looks like I may have to go that route.