Anyone good with 2 stroke engines?

[Harleyboy]

Hi,

I have a 2015 Stihl FS38 strimmer. It doesn’t run right and is doing my head in!

Put a new carb on today and it fires up fine and revs well but only for a minute or so. Then it dies. It has freshly mixed fuel at 50:1 and no fuel line/filter issues. Once cool it starts again but only for a short time.

Google suggests spark arrestor but mine has nothing that sticks out as some do on the net. I’m at a loss and am ready to ditch for a cordless one.

Any ideas?

[Chris32345]

Is the choke working correctly?

[GreenV8S]

That sounds like a mixture issue. You could confirm that by giving it a burst of aerosol oil or cold start spray while it is warming up and seeing whether that accelerates the problem. If so, it may be the carb isn't adjusted correctly. Did it come with directions to set the jets?

[Harleyboy]

The choke is very basic - bit of plastic on a lever shuts off the air.

Mixture could be wrong. No instructions came with the carb and I haven’t adjusted it. It was the same issue I had with the last carb and it is possible that the mixture was wrong with that too. I’ll try adjusting the high speed screw

[bigothunter]

Air leak in the inlet tract due to a damaged gasket or O-ring?

Idle mixture has screw adjustment but usually part and full load mixture will be controlled by a fixed main jet.

[stevieturbo]

Is it the correct carb ? Is fuel getting to it ok ? Are you sure there are no air leaks between carb and engine ?

[littleredrooster]

If it peters out gradually, fuel issue.
If it dies pretty much immediately, electronics - ignition trigger or spark generator (whatever it's got).

After it stops, is there still a good spark when you try to restart it? Is the plug getting wet?

[GreenV8S]

Knowing a different carb had the same problem is a pretty important clue.

How is the fuel pumped? Sometimes they're pumped via an exhaust pulse and this can stop working if the diaphragm goes hard.

[bigothunter]

GreenV8S said:

Knowing a different carb had the same problem is a pretty important clue.

How is the fuel pumped? Sometimes they're pumped via an exhaust pulse and this can stop working if the diaphragm goes hard.

OP has put on a new carb. Surely the pump diaphragm is integral to this new carb?

[Zener]

Sounds like ign failure did you check it still as spark when it dies?