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Echo PB755t losing power at full throttle

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CTmower

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Discussion starter · #1 ·
My Echo backpack blower started to slowly lose overall power. Now at full throttle it still blows but it only feels like its at half or 3/4 power. I tried spraying Seafoam into the intake and it seems to do its cleaning then get the RPM's way up there for about 10 seconds then it just declines back to its troublesome ways.
Blower is about 4 years old. Just changed the spark plug last year, banged out/cleaned out the air filter. Also checked the spark arrestor and the was crystal clear, no buildup at all. I've never winterized my 2 stroke machines, pretty much how I leave them after my last job of the year is how I pick them up at the beginning of the next season.
Would it be cheaper for me to just buy a new carb or is there a simple fix??
I was thinking about buying a new spark plug, air filter, and gas filter to see if that helps at all. Any help would be appreciated.
 
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#2 ·
There is a plug on the side of your carb. Takes a special tool to pull out. Behind that plug is your carb adjustment. Probably needs to be adjusted. plug is right above where fuel lines go into carb. Also check your fuel lines are'nt collapsing from the inside out.
 
#4 ·
Just purchased the Echo755 the other day, and the echo rep was there for the big sale going on. He told me to make sure, I don't run low speed for too long ,because you can get carbon build up in the exhaust /precat system,. Might want to look that over. He told me I should do a high speed run after running low speed for a while . Its all the lovely emission pieces their adding.
 
Discussion starter · #6 ·
Just bought a new gas filter and air filter. Will install tomorrow and give it one more dousing of Seafoam. Hopefully she works if not I'll have to bring her in for a new carb or carb adjustment I think.
 
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Discussion starter · #9 ·
Yes took exhaust off and there was no build up behind it. Spark arrestor was also clean n clear.
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Discussion starter · #12 ·
So I've replaced the air filter, gas filter, sprayed the **** out of the carb with Seafoam, and she still runs at half power at full throttle. However if I keep the choke at 1/2 choke the blower will run at FULL power!!!! My local repair shop said they'd charge $25 for a simple carb tune up. Unless I can get to the adjustments myself I might just spend the money.
 
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#13 ·
CTmower said:
However if I keep the choke at 1/2 choke the blower will run at FULL power!!!!
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Which is a symptom of an air leak.

To verify this, you will need to spray some carb cleaner or breakcleaner with the little straw around the base of the cylinder, where the carb meets the isolation block and where the isolation block meets the cyclinder. You should notice a change in the way it runs.

Chances are that the isolation block is bad, they warp. To fix this you can buy a new Isolation block and gaskets.

Or, you can take the isolation block, and with some fine sand paper (220 or better) or emery paper and a perfectly flat surface. Make some passes on both sides to where it looks flat. New gaskets and you should be good to go.
 
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#14 ·
I gotta disagree. Its a lean adjustment condition. Choking let's less air in, hence creating a richer condition. Get to the high speed screw. Air leaks run crappy at all rpms. Back when you could get to low and high speed screws you didn't see all these problems.
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#15 ·
Patriot Services said:
I gotta disagree. Its a lean adjustment condition. Choking let's less air in, hence creating a richer condition. Get to the high speed screw. Air leaks run crappy at all rpms.
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Okay, he is getting to much air, or not enough fuel with the choke fully open. he can take the cap off of the high speed screw and adjust it. To try and balance out the mixture.

So here is my question, what is causeing this imbalance ? I don't think the high speed screw can move with out some human intervention.

And like I said, he needs to verify that it is an air leak. There could be other problems.....One step at a time.

Patriot Services said:
Back when you could get to low and high speed screws you didn't see all these problems.
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Damn EPA
 
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#16 ·
I had a back pack ,Redmax, doing similar thing, It would run good when you first start it & run for a while but when it got warm it would bog down at full throttle,, turns out there were no air leaks,no carb issues, it was just plain worn out! had to buy a new one...cost allmost as much to have it rebuilt...
 
#17 ·
Strangely enough, and it has been discussed around here before, but a few of us have learned to NOT leave our RM blowers in the sun b/tw jobs. 'Seems' the gas will percolate a bit in the fuel lines making for a rough restart and lack of full throttle for awhile on a warm-ish restart. Solution? Put blower in the shade somehow...voila. Using the primer will refill the lines to a degree, but this shade technique eliminates this priming of a warm-ish engine.
 
#18 ·
Valk said:
Strangely enough, and it has been discussed around here before, but a few of us have learned to NOT leave our RM blowers in the sun b/tw jobs. 'Seems' the gas will percolate a bit in the fuel lines making for a rough restart and lack of full throttle for awhile on a warm-ish restart. Solution? Put blower in the shade somehow...voila. Using the primer will refill the lines to a degree, but this shade technique eliminates this priming of a warm-ish engine.
Click to expand...
Old as engines themselves. Used to be very common in cars with carbs. Us old timers call it vapor lock.
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Discussion starter · #19 ·
So I've replaced everything possible... Air filter, spark plug, gas filter, and I sprayed the crap out of the carb with Seafoam. Still only half power at full throttle but i'm able to get full power with half choke on. At this point I can either bring it into my local shop and have the carb taken apart and cleaned for probably $25-50 or I can just buy a brand new carb for $55 and install it myself. At this point sounds like a no brainer to just buy a new carb.
 
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Discussion starter · #20 ·
Also forgot to mention when I spray the Seafoam in the carb the blower goes up to full power but then slowly goes back down to its weak current state. Going to try and access the high speed screw and see if that changes anything.
 
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CTmower
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