echo pb-500 backpack blower bogs at full throttle

[JONSSTIHL]

thanks for the p/n on the tool. I replaced the screen when I put the kit in but nothing looked really dirty when I had the carb apart.

I will check out the seals this week end after getting the wifes winter tires on her car.

the intermittent nature of the problem makes me think it is not an adjustment issue. just took a quick look at the ipl and there doesn't seem to be an impulse hose to tap into to pressure test the case.

 

[Saw Dr.]

Just put your air chuck in the spark plug hole and blow some air in. It will be pretty obvious if that seal is leaking. Soapy water will make it even easier to see.

 

[Giles]

My leaf blower has started giving me trouble lately. It slows down at full throttle


It runs fine until it gets warm, maybe 5-10 minutes then it starts slowing down at full throttle every once in a while until it gets progressively worst and eventually I can't get it to run at full throttle. I can keep it running by letting off the throttle for a few seconds then returning to wot. the problem is intermitent so I can get the job done it just takes longer.


I checked the screen in the exhaust but it wasn't very dirty. I also took the carb off and sprayed it down with carb cleaner. found out it is a strato design and the strato barrel valve in the carb had a bit of oil mix in it so I sprayed everything inside and out with carb cleaner without disassembling it.


I did a search and found out it has reed valves so maybe something is wrong with them but other than the basics I have no clue where to start. The plug is a nice tan color with a little carbon buildup. no obvious fuel leaks, fuel filter is new from last year.

Where do I look next?

I have a Husqvarna backpack blower that was doing the same thing. I cleaned the carb--same problem. This model has NO adjustment screws!!
I removed the original fuel filter and cleaned and blow it out. Removed the muffler screen and discovered it has a catalyst muffler. I could see that it would be major to do a muffler mod, so I decided to just leave the screen out.
Bingo---used it all day yesterday with no problems.
If the problem returns, I will gut the muffler.

 

[z71mike]

I have a Husqvarna backpack blower that was doing the same thing. I cleaned the carb--same problem. This model has NO adjustment screws!!
I removed the original fuel filter and cleaned and blow it out. Removed the muffler screen and discovered it has a catalyst muffler. I could see that it would be major to do a muffler mod, so I decided to just leave the screen out.
Bingo---used it all day yesterday with no problems.
If the problem returns, I will gut the muffler.

Can't gut the muffler if you can't adjust the carb to compensate.

 

[Giles]

You are correct. But I can change the crappy carburetor to compensate.

 

[rmh3481]

The barrel carbs are adjustable. Their fuel needle travels down through the barrel. Recessed at the very top is a small plug that covers the needle. Raising the needle adds fuel.

Here are the walbro service manuals;
http://wem.walbro.com/distributors/servicemanuals/

Select wyk and notice in the diagrams the needle running down through the barrel. The top acts as a ramp and raises the needle as the venturi opens.

 

[z71mike]

The barrel carbs are adjustable. Their fuel needle travels down through the barrel. Recessed at the very top is a small plug that covers the needle. Raising the needle adds fuel.

Here are the walbro service manuals;
http://wem.walbro.com/distributors/servicemanuals/

Select wyk and notice in the diagrams the needle running down through the barrel. The top acts as a ramp and raises the needle as the venturi opens.

Yes, but you're still stuck with a static main jet.

 

[LegDeLimber]

Hang on Guys, it's a walbro, WLA-1 on mine. For some reason I can't see a diagram of any of these series carbs, on the walbro pages.
But the FeeBay link has some shiny new pics of one.
http://www.ebay.com/itm/Echo-OEM-Carburetor-PB-500-Walbro-WLA-1-New-/140443261671

That black , barrel type section at the top is the air valve.
it feeds the two reeds through those hoses that hug the jug
and have a reed in each port cap on the cylinder sides.
Quad transfers, but one port on each side of the jug is favored to feed from the reed.

You can see the carb is still a throttle plate or shutter, type.
It alss feeds into the case via a dual petal reed.
I'm beat right now guys but gimme some time and I'll try find the photos i took
as I tore mine down, thinking of maybe brave enough for a thread on it.

And I 'm still grubbing about for the needles and the number.
I had Realy nice neighbor come over to help around the house, brought me groceries and "straightened up" a bit WITH my permission and blessing ( after the knee port&polish job)
But.... between that and the "mini blackouts" I had with the first pain meds
I'm here to tell you guys it's like having Alzheimers at an Easter egg hunt.

 

[LegDeLimber]

Here is the link to those elusive WLA-1 needles.
echo/shindaiwa # P003001130, H Needle same needle fits both holes guys.
http://www.ereplacementparts.com/h-needle-p-505315.html
When I went to dealer and orderd it took over 2 months for them to get here.
Order an get the needles in your hands first, then you can twirly tool those mini "D"s out.

 

[z71mike]

I wish my WYA-155 was that easy!

 

[LegDeLimber]

Is that WYA on a Redmax blower? I've got a few lean seized carcasses here that I grabbed a couple years back.
For what it's worth, the needle on these older carbs is adjustable. Just the main jets were apparently a couple sizes too small.

 

[Saw Dr.]

All of the adjusting in the world will not solve this guy's issue of the seal is out. We tried on the first wonky one until we figured it out.

 

[z71mike]

Is that WYA on a Redmax blower? I've got a few lean seized carcasses here that I grabbed a couple years back.
For what it's worth, the needle on these older carbs is adjustable. Just the main jets were apparently a couple sizes too small.

Yes sir. The main jet is the problem. I don't know why they did that. Terrible design. That's why I'm trying to find an adjustable replacement.

 

[JONSSTIHL]

replaced the fuel line this weekend and it worked well for 10 minutes then the dreaded drop in rpm showed up. I managed to finish the job with it and so I'm done with it for this year. I will take it back to the dealer before the warranty is up this spring. hopefully they can find the trouble.
I also took off the starter assembly and it looked awfully clean in there, I don't think the seal is leaking.

maybe it is the ignition module because sometimes the rpm drops fast as if someone hit the kill switch but if I let off the throttle it idles fine. the ony way to get it to die is to hold the throttle down while it bogs.

 

[LegDeLimber]

JONSSTIHL Just for giggles, swap in a fresh fuel filter or backwash the current one
through the hose nipple, using something like carb or brake cleaner
and then Very Gently with a light touch blow it out with air.
You don't want to blow it apart with a heavy blast,
just a very light puff to push out the cleaner solvent and see that everything looks clean
and no nasty gummy deposits still in it.
That's all it took to stop that persistant bogging in my 413 that was much like what you've described.
The 413 is a unit I picked up as a parts donor for the 620 ( lots of common parts)
But after I got it home gave it a more thorough inspection , I realized it was in darned good
condition other than carbon clogged exhaust port.
point here is that it was doing that run for 10~12 mins and falter a bit, but getting worse.
Shorter time till next bogg and almost die each time until you let it idle a moment.
Loosening the fuel cap didnt help, So I grabbed a spare fuel filter and did the cleaning routine
and swapped it in and Bingo! end of problem.
Hey, come on it's cheap and easy to try!

z71mike I saw where you've asked the lawnsite crowd for ideas. I checked the jet in that carb in my photo and it seems to be the #61 jet. I also remember seeing some shortblock kits for the 8500 redmax last year on feebay
and the kits included a larger main jet.
I didn't see any listed with the jet kit, when I looked a couple nights ago.
so I guess it's time to grab a micro drill index kit and the #63 jet and just have a little fun.

For what this is worth, I swapped a metering body from the redmax blower carb
onto the Echo PB-500 carb. This setup would let me adjust the pb-500 to a rich/light four stroking condition.
I was planning to raise the metering lever a small bit and see if that would get the extra fuel
to fatten up the top end, but had the other metering body laying loose so I just tried it first.
I'd expect we'd be better off to just drill out the main jet on the pb-500 rather than lifting the metering lever though as it could throw the mixture too rich in other speed ranges

 

[z71mike]

z71mike I saw where you've asked the lawnsite crowd for ideas. I checked the jet in that carb in my photo and it seems to be the #61 jet. I also remember seeing some shortblock kits for the 8500 redmax last year on feebay
and the kits included a larger main jet.
I didn't see any listed with the jet kit, when I looked a couple nights ago.
so I guess it's time to grab a micro drill index kit and the #63 jet and just have a little fun.

I'm on the lookout for another carb so I can drill it. Really don't wanna drill out my one-week-old unit under warranty, in case I need to slap it back on for some reason. Waiting for the right deal to come around.

 

[JONSSTIHL]

The machine is on it's third fuel filter. including the brand new one that is on it now.
I even tried a different batch of fuel mix thinking maybe it was bad but still the same symptoms.

one problem I may have is that when I cleaned out the carb I couldn't take out the mixture screws so maybe there is still a speck of something in the carb.

 

[LegDeLimber]

I'm on the lookout for another carb so I can drill it. Really don't wanna drill out my one-week-old unit under warranty, in case I need to slap it back on for some reason. Waiting for the right deal to come around.

I can take a look in my carcass pile and see if there's nice looking one.
Sorry for not reading this and posting sooner, i've been stuck somewhere that I couldn't get online.

 

[ackack]

New member & reviving this thread after a few months. Picked up a PB-500 off Craig for next to nothing. Piston & cylinder scored so I replaced but am still easily "in the money" vs a new blower. However, am having the same carb problem some have experienced ... only runs on 1/2 choke (but erratic) & stalls immed. when choke is moved to "run." Since the jug is new, there is no carbon at the exhaust port & the muffler looks good; arrestor is clear. Rebuilt the carb w/kit (also sprayed w/ cleaner & air blew it, plus ran it through ultrasonic cleaner), new fuel filter & lines. Did pressure/leak test w/air into cylinder & no leaks, crank seals solid. Thus, I suspect that the carb needs adjusting ... only thing left? LegDeLimber has great solution of swapping the "d" needles for Shindaiwa notched needles and they do look the same except for the head. He says "you can twirly tool those mini "D"s out." I tried an 22-18 electrical butt connector and it did slide over the "d" head but was not tight enough to twist the needle ... it just spun around it. Any other suggestions for extracting the "d" heads?

 

[backhoelover]

tech school tough us that the reed valve has to be adjusted just right
ill send you the spec as soon as i can find them