Stihl FS 85T dies off choke

[Waorani]

I've had this for several years but it probably only has a few total hours. Most recently it sat unused for over a year while the guy that was supposed to be taking care of my place while I was gone didn't. Gas in tank gone and lots of varnish. Cleaned everything up, replaced primer bulb, fuel lines/filter, and rebuilt carb. Initially wouldn't prime but took carb back apart and may have had a diaphram in backwards. Now priming and starting fine but dies as I take off choke.

I've got another trimmer but would really like to get this going again just to use the polesaw attachment I've got for it. Obviously there's still a problem with the carb - maybe some gunk I didn't get but the carb seemed surprisingly clean when I dug into it. Thoughts, suggestions, point in the right direction? Alternatively, good source for a new Zama C1Q-S45 carb?

 

[D'Animal]

How did you clean and rebuild the carb?

 

[Weedhopper]

I deleted my above post cause I saw you replaced the fuel lines.

Still, look for any air leak that may be causing loss of suction. Also check to be sure the gas cap is venting.

 

[D'Animal]

To follow up with Weedhopper's comments, a few things come to mind.

The gasket behind the carburetor has a small diameter hole in it. The black intake manifold that the carburetor bolts too has the impulse passage in it. Make sure the gasket is on correctly and not blocking the hole.

Make sure the fuel lines are connected propely. If the discharge line (the one coming from the primer bulb area) is connected to the suction line, it will not run for line.

You mentioned the carburetor was clean inside, there are probably fuel deposits tht varnished in the tiny jet holes of the carb. Did you use brake clean or carb spray to clean the carb?

It is a Zama carburetor, make sure the welch plug glue did not come from around the welch plugs inside the metering chamber of the carb. It is common and what will happen is the veturi will suck air instead of fuel. Re-seal the welch plugs with superglue and it should be fine.

 

[Waorani]

Thanks, I will check all the suggestions. I cleaned with carb cleaner and installed new carb kit. I did not replace the welch plugs because I didn't think I could set/seal the new ones (perhaps there's some gunk under that I missed.

I made a drawing of which hose went where but I may have screwed it up. When it initially wouldn't prime, I swaped the hoses and was able to get it to prime and start on choke. They still could be backwards though.

 

[D'Animal]

Your concern of sealing the welch plugs is a good one.

ZAMA has a hard time sealing them. Many of the "Good" carb cleaners will clean off the glue or sealant and it will draw air through the area around the welch plug. I have seen new carbs do it.