Help needed: Shindaiwa M242 gas trimmer

[ahdofu88]

Hello,
On my gas trimmer if I were to let the engine run at idle for a while, at some point it will refuse to pick up speed when I pull on the throttle. It bogs down and dies. However I have noticed that removing the gas cap, fixes the issue. I thought perhaps the check valve was the issue but replacing the check valve did not solve the issue. Next was the carb itself and the fuel lines so I ended up replacing the carb, fuel lines and the filter. That did not do it either. Does anyone has any ideas what might be wrong?
Thanks,
Matt

 

[CraigH]

If removing the fuel cap fixes the problem, I'd be guessing that it's the breather vent on the cap not working. Have you verified that the fuel cap vent is actually working on either cap?

 

[ahdofu88]

Thanks for the quick reply CraigH. The cap does not have a breather vent. It is a solid, one piece cap.
I forgot to mention that I have also checked the spark arrester screen and the screen is clear.

 

[MParr]

Thanks for the quick reply CraigH. The cap does not have a breather vent. It is a solid, one piece cap.
I forgot to mention that I have also checked the spark arrester screen and the screen is clear.

It sounds like a venting issue. Did you change out the vent tube filter? Most trimmers have 3 fuel lines on them. One line is the pickup line and it delivers fuel to the carburetor. There will be a small filter on that line and it goes in the fuel tank. There is one return line. There is one vent line. The vent line has a small filter on it too. This filter prevents trash from entering through the vent. If you didn’t change the fuel filter and vent filter, I would do so.
Did you use this fuel system kit?

84000Y | Shindaiwa-USA.com

www.shindaiwa-usa.com

 

[StarTech]

The trimmer has a separate tank vent. That is if someone hasn't remove it and plugged the line.

 

[MParr]

The trimmer has a separate tank vent. That is if someone hasn't remove it and plugged the line.
View attachment 65227

Yep! That’s why I posted my reply and the link to the fuel kit.
The fuel kit is very similar to the one that I just put in my Echo string trimmer.

 

[ahdofu88]

The vent valve (which I had referred to as the check valve in my post) was the first thing that I had replaced but that did not solve the issue.

 

[bertsmobile1]

IT is a 2 way system
The tank has to hold 3 to 5 psi of pressure to force the fuel into the carb
However as the fuel level drops air has to get into the tank to replace the fuel or you will get a vapour lock
Check out Joe Pace 2 stroke diagnostics on the evil You Tube

 

[ahdofu88]

I checked out the YouTube video. On that specific application the gas cap has a vent. On mine there is no vent. It is a solid cap. Having said this, I did not think that the tank actually held any pressure. In other words I was under the impression that the carb diaphragm pulled fuel in. I'll reach out to Joe and see what he says. Thanks for sharing the link.

 

[StarTech]

IT is a 2 way system
The tank has to hold 3 to 5 psi of pressure to force the fuel into the carb
However as the fuel level drops air has to get into the tank to replace the fuel or you will get a vapour lock
Check out Joe Pace 2 stroke diagnostics on the evil You Tube

Then why is there a fuel in the carburetor?