SRM 225 won't rev up.

[Geardrive1]

Hello everyone, I'm new to this forum. I have a problem with an Echo srm225 trimmer.

It's about 7 years old and I use it about twice a month. I always empty the tank and idle untill it dies.

About 2 years ago it started running bad, so I bought a gasket kit and took apart the carb blasted it with brakekleen and air also drilled out the plug to adjust the air and fuel. It ran fine till about February of this year. So, I finally ordered a new carb from Amazon and it ran great till last month.
The problem was that I would have to keep the choke way up to keep it running. Till it would not start period. So I ordered another carb. (different brand). I installed it, changed the air filter and the fuel filter and removed the muffler soaked it in solvent overnight and cleaned it, changed the fuel lines the spark plug. and it does the same thing.
It idles great, and it somewhat revs up when it is dead cold but as soon as it warms up it won't rev up. This carb has a plug on the air to fuel mixture screw so I did not attempt to remove it in case I have to return it.
I removed the gas cap also.
It will idle for great for a long time but I can't get to rev up it just stumbles wherever ever the choke lever is at.

Thank You , any thoughts would be greatly appreciated.

 

[Rivets]

Have you check to see if the spark arrester is not plugged?

 

[StarTech]

This what you get by buy China clones. But as Rivets suggest check the spark arrester first.

But just for fun which of the 16 serial breaks for the SRM-225, 14 serial breaks for the SRM-225i, 3 serial number breaks for the SRM-225SB, or the 6 serial number breaks for the SRM-225U is it? And do you have tach and tape measure for tuning?

 

[Geardrive1]

I don't know what a tach and tape measure is for tunning, the spark arrester is long gone.

 

[hlw49]

Did you check the exhaust port in the cylinder to make sure it is open?

 

[StarTech]

I don't know what a tach and tape measure is for tunning, the spark arrester is long gone.

Well there is specific tuning instructions from Echo requiring specific string lengths and rpms. Strings length spec is for proper loading of the engine during the tuning process.

These specs can be different depending the model and serial numbers as there were four different carburetor used on this and the tuning is done with a Speed Feed 400 trimmer head. The main adjustment to set the idle mixture rich for a specifed rpm drop from max idle speed.

Here is just a sample what the Echo/Shimdaiwa should using to tune these engines.


So there is more involved than what the average user knows. Without proper adjustment engine damage can occur. Specially if you run with the mixture too lean.

 

[Tiger Small Engine]

Well there is specific tuning instructions from Echo requiring specific string lengths and rpms. Strings length spec is for proper loading of the engine during the tuning process.

These specs can be different depending the model and serial numbers as there were four different carburetor used on this and the tuning is done with a Speed Feed 400 trimmer head. The main adjustment to set the idle mixture rich for a specifed rpm drop from max idle speed.

Here is just a sample what the Echo/Shimdaiwa should using to tune these engines.
View attachment 66643

So there is more involved than what the average user knows. Without proper adjustment engine damage can occur. Specially if you run with the mixture too lean.

Hopefully you didn’t throw away the OEM carburetor. Clean it thoroughly and replace metering diaphragm. So you are going to return a $20 carburetor that has been used? Take the low and high plugs out if necessary are adjust the darn thing. The fact that you know those hidden screws are there is amazing to me. Pull the muffler and check the condition of the piston, rings, and cylinder.

 

[Rivets]

The spark arrester is under the muffler, not on the outside. Did you remove the muffler to check it. When you remove the muffler you can check the exhaust ports as suggested. This site shows the location. https://www.partstree.com/models/srm-225-echo-string-trimmer-sn-s03912001001-s03912999999/exhaust-5/

 

[StarTech]

Rivets, The spark arrester when present is under a deflector cover; NOT under the muffler. You got it in your mind wrong. On the diagram it is held by 5 screws. All the OP had to do is remove the engine shroud to access it. The two main muffler screws are never touched unless the muffler is being removed. These 5 screws can be a pain to remove depending how rusty things are.

Now there are time the defector can be removed without removing the shroud but it is much with the shroud removed.

 

[Rivets]

Star, you are correct, haven’t finished my first cup of coffee yet. Sorry about the terrible post.