Need a good trim

[Coelacanth64]

Folks,
I have a Craftsman Model#316796170, gas trimmer, pole saw, tiller combo device, from circa 2006.




The machine will start normally, it will run at about 1/2 throttle, but it stalls when the trigger is pulled to wide open.
I noticed that the gas line was rotten, so I replaced it. I also installed a new gas line filter. The primer plunger is fine.
I mixed new fuel/oil mixture and filled the tank. I cleaned and re-oiled the air filter and re-inserted it.
I removed the carb and checked the choke mechanism. It seems fine. The throttle moves normally.
I also filled the sump with fresh oil.

I could not locate a replacement spark plug (RDZ19H) locally, so I ordered one. But, given that the machine will start on first pull, I’m doubtful that the plug is the issue.

I have not yet disassembled the carb completely. Is there a port that might be partially blocked?

Any suggestions are more than welcome.

Best,
Jack

 

[dougand3]

It's a 4 stroke. Manual says DO NOT put oil in the fuel. It has a 3.04oz sump for SAE 30. It may have run on 2 stroke fuel and got really carboned up. If fuel lines broke, I'm sure carb diaphragms are stiff and passages blocked. So, cleaning and rebuild time or a new carb.

 

[olgeezershonda]

As mentioned it's a 4 stroke. Make sure to do an oil change as well.

 

[Coelacanth64]

Yes, 4 stroker.
Changed the oil in the sump.
Tore carb down, cleaned/reamed out everything. No change.
Not sure how to tell if diaprams are stiff or passages are blocked.
If so, would it start normally or run at idle?

But, yes…I think a new carb is in the offing.
Thanks for the help!

 

[dougand3]

The metering and pump diaphragms need to be very supple. If they "clack" at all - they are too stiff. It may start but won't throttle up with stiff diaphragms. A WYL-19 rb kit is $6. A new AM carb is $10.

MTD 75305251 Carburetor w/ Primer​

 

[Coelacanth64]

Does this diaphragm fail the test?

 

[dougand3]

Hard to tell just looking. With other hand - move it. Is rubber supple or does it clack? Unscrew phillips head and remove lever, pin, needle and spring to clean. DON'T LOSE SPRING. Put a finger on lever as you unscrew phillips.

 

[Coelacanth64]

Did that last week. All clean now.
I’ll check the diaphragm for flexibility.
Or, I may just replace the carburetor.

 

[dougand3]

While waiting on new parts...try soaking metering diaphragm in Marvel Mys Oil. I've gotten a little flexibility back that way and gotten a machine running. Not ideal - new is better. And on the other side is the fuel pump diaphragm - thin acetate. It may be stiff, too, and will need repalcement.