Ryobi gas trimmer stalls when lowering the revoutions

Typical fuel line routing is:

One line (the one with the fuel filter in the end of it) comes out of the fuel tank and goes to the bottom fitting on the carburator. The second line comes out of the tank and goes to the bottom fitting on the primer bulb. The third section of line goes from the top fitting on primer bulb to top fitting on the carburator. Hope this helped and best wishes.

Typical fuel line routing is:

One line (the one with the fuel filter in the end of it) comes out of the fuel tank and goes to the bottom fitting on the carburator. The second line comes out of the tank and goes to the bottom fitting on the primer bulb. The third section of line goes from the top fitting on primer bulb to top fitting on the carburator. Hope this helped and best wishes.

You can buy new Line to re-spool on your existing head

The carburator needs to be adjusted a little, thin our your mixture screw when the trimmer is warmed up and idling. Well how do you get it to idle? I usually have to play with the choke lever with the throttle wide open going from choke to partial choke as needed to keep it running. Adjusting can be tricky, you need a small screwdriver. Screw all the way in then back out 3 to 3.5 turns. this should get you close. Adjust idle as needed.

To get the original parts:
http://www.ereplacementparts.com/ryobi-725r-41bd725a734-handheld-trimmer-parts-c-7931_15633_18592.html

I just rebuilt my 725r. I don't have a diagram but I can explain it. There are two lines coming out of the fuel tank. The line closest to the rear is the fuel feed and has the in-tank filter (these are available for replacement). This line goes through the lower case hole of the air filter housing and attaches to the bottom of the carburetor. The line toward the front of the tank attaches to the longer/lower fitting the primer bulb and is the return. The line coming off the shorter/upper fitting of the primer bulb goes through the upper hole of the air filter housing and attaches to the top of the carburetor.

FYI also, the forward carburetor screw is the low idle adjustment & the rear, the high-speed mixture. The original oil mixture spec called for 32:1

The lower flex shaft should cost around $40, unless you order it online and have to pay shipping. You should be able to get one from your local MTD dealer. (Ryobi is owned by MTD)

I have the same issue of clutch removal on a Ryobi 725r. Actually the clutch finally died after many years of use.
Instead of using a screwdriver to hold the piston I recommend using a piece of clothesline rope. It will be easier on the internal components and won't scratch up the cylinder walls or piston. Just be sure to leave a small amount hanging out of the spark plug hole so you can pull it out afterward.

The gas nipple that come out I have...whats goes in the other hole?

Ryobi is Japanese for "Piece of ****" My suggestion is to throw it out!
My 767r has had fuel line and carb trouble from day one. I'll never buy another Ryobi or Craftsman tool again.