Echo SRM-266 won't rev up

goosemasterkl

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I have an Echo SRM-266 trimmer and it won't rev up. It will run about half throttle; seems like it doesn't have any power. I've changed carburetors, put new fuel lines and filter on it. Put new plug in it, took the muffler loose and it still won't power up. It has 70 lbs. compression. Could a weak coil or air gap be off causing this problem? It sounds fuel related to me but I'm stumped. Could someone offer me some good advice? Thanks in advance to anyone who responds.
 

bertsmobile1

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If that compression figure is accurate ( seldome are without special fittings ) then you are lucky it starts at all.
Remove the muffler and try again.
Goes OK = Muffler blocked
No difference then get a good torch and check the piston & bore for grooves.
 

jp1961

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The muffler usually has a fine screen (spark arrester), these can carbon shut, which would cause your problem. There also is a species of wasp that loves to build it's clay nest in small holes. check for that too.

Regards

Jeff
 

cpurvis

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The muffler usually has a fine screen (spark arrester), these can carbon shut, which would cause your problem. There also is a species of wasp that loves to build it's clay nest in small holes. check for that too.

Regards

Jeff

I have a 20+ year old Echo string trimmer, model 225 (I think). That screen clogged, I cleaned it and it ran fine again. It clogged again and I gave that screen the heave-ho. Haven't had a recurrence of that problem since.

Not sure what government agency mandates that spark-arrestor screen but it really serves no useful purpose for the user trimming green grass. If I was weed-eating in some dry-as-tinder National Forest, I probably would have replaced it. But I'm not.

Also, don't run the fuel/oil mix any richer than what the manual specifies. 50:1 in my case.
 

jp1961

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One more item to check is the high speed needle on the carb. I'm not sure if it's a Walbro or Zama, but try turning the high speed needle in. Some carbs have plastic limiter caps which limit how rich or lean the engine will run (another government fuster cluck,,,lol), and some of the newer Walbro's have needles with no slot in them at all to prevent the homeowner from making any adjustment at all (for which I've machined a special tool to grip the needle and allow for adjustment).

Regards

Jeff
 

snowbelt_subie

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One more item to check is the high speed needle on the carb. I'm not sure if it's a Walbro or Zama, but try turning the high speed needle in. Some carbs have plastic limiter caps which limit how rich or lean the engine will run (another government fuster cluck,,,lol), and some of the newer Walbro's have needles with no slot in them at all to prevent the homeowner from making any adjustment at all (for which I've machined a special tool to grip the needle and allow for adjustment).

Regards

Jeff

i agree most people dont know that echo carbs are adjustable idle mix is a tiny sqrew down in the rotary hole on top of the carb. the high speed is right below the primer bulb.

need very tiny sqrew drivers to adjust.
 

bertsmobile1

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i agree most people dont know that echo carbs are adjustable idle mix is a tiny sqrew down in the rotary hole on top of the carb. the high speed is right below the primer bulb.

need very tiny sqrew drivers to adjust.

Not all rotary valve carbs have adjustable idle needles and or main jets.
They are illegal in several states that mandates non adjustable carbs.
Unfortunately it also means you can not clean them properly either.

And Echo do not make carbs they fit one from one of the carb companies.
And in this case it is a Zama RB series with a high speed needle hiding under a cover under the Purge bulb and an idle needle hiding under a limiter cap that you have to prise off the top of the rotary valve.
 

Timbro

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i agree most people dont know that echo carbs are adjustable idle mix is a tiny sqrew down in the rotary hole on top of the carb. the high speed is right below the primer bulb.

need very tiny sqrew drivers to adjust.
Thank you so much for this info!! I just put a cheap carb on my trimmer and while it ran ok, it didn't have enough power at full throttle. I found the high throttle screw you mentioned, tightened it down a bit and now it runs like new!!
 

Tiger Small Engine

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Thank you so much for this info!! I just put a cheap carb on my trimmer and while it ran ok, it didn't have enough power at full throttle. I found the high throttle screw you mentioned, tightened it down a bit and now it runs like new!!
Always try to keep and clean original carburetor before changing. Heat up spark arrestor if clogged to regain full wide open throttle. Pull muffler and check for scoring on piston, rings, and cylinder if the above don’t fix issue. I check condition of piston, rings, and cylinder more often than you would think. From what I hear, many shops never even pull the muffler and just start throwing parts and labor at it.
 
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