Oil & Fuel Rough Idle - Carb Issue

[SRB331]

Good evening all.
Just sharing some info in case someone else runs into this problem. 2007 PT425 with a Robin EH72 engine running really rough and on throttle up she would bog down. Removed carb, cleaned all ports (or thought I did) and soaked in carburetor cleaner for an hour. Blew out all ports with compressed air, allowed time to dry, re installed carb with new accelerator diaphragm. After a couple of hours of operation same problem happened again; Running really rough with black smoke at idle. Dissembled carb again to see if I missed something during cleaning and sure enough found the end of the "slow jet" (item 20 on Fig. 710 of the PUB- EP1549 Parts Manual) partially plugged. Really small orifice. Had to clean it with a strand of copper wire. Reassembled and she's running great again. I think I had multiple issues. Dirty jets and a worn accelerator diaphragm. Hope this helps anyone with the same issue.

 

[J_J]

Do you have a fuel filter in the fuel line?

 

[MossRoad]

Good evening all.
Just sharing some info in case someone else runs into this problem. 2007 PT425 with a Robin EH72 engine running really rough and on throttle up she would bog down. Removed carb, cleaned all ports (or thought I did) and soaked in carburetor cleaner for an hour. Blew out all ports with compressed air, allowed time to dry, re installed carb with new accelerator diaphragm. After a couple of hours of operation same problem happened again; Running really rough with black smoke at idle. Dissembled carb again to see if I missed something during cleaning and sure enough found the end of the "slow jet" (item 20 on Fig. 710 of the PUB- EP1549 Parts Manual) partially plugged. Really small orifice. Had to clean it with a strand of copper wire. Reassembled and she's running great again. I think I had multiple issues. Dirty jets and a worn accelerator diaphragm. Hope this helps anyone with the same issue.

Good, helpful troubleshooting! :thumbsup:

 

[SRB331]

Do you have a fuel filter in the fuel line?

Absolutely. I don't put a lot of run hours on her so I change the fuel filter every other year. Seemed to be more of a gumming issue than dirty fuel or sediment.

 

[pajoube]

What state are you located in? Welcome to the forum.
PJ

 

[Marks481]

Absolutely. I don't put a lot of run hours on her so I change the fuel filter every other year. Seemed to be more of a gumming issue than dirty fuel or sediment.

Put an in-line valve on the fuel supply line near the carburetor. Shut the valve and let the motor run until it dies. That way you aren't left with fuel drying up in the carburetor bowl, and leaving residue behind. That is what I do with all my small engines.

 

[SRB331]

Great Idea Tmarks11. I already have a fuel valve installed and shut off when not in use. I'll start letting the bowl run dry to shut'er down.

JJ, I've been around awhile, just don't get online too often. At the moment I'm living in MA.

 

[ponytug]

Thanks for sharing!

FWIW, I use Sta-Bil in all of my gasoline engines to help prevent gumming. I also tend to run carb/injector cleaner in the fuel on a regular basis- mostly because I think dealing with fuel jets is such a pain and I will do a lot not to have to pull injectors.

All the best,

Peter