Full Crank Engines

Depends how you look at it. Even most of the rotary carburetors do have a idle mixture adjustment even though they don't have separate idle jet. Plus you have a lower torque level by dropping the 5cc.
 
Plus I hope you're going with the 2 cycle version as 4 cycles around here are just not holding up. It is results of not oiling properly due inverted and sideways operations. The only 4 cycle trimmers that are holding their own here is the Stihl 4-mix versions that still uses a 2 cycle mix.
 
On top this most of the newer Ryobi are basically non repairable when comes to engine as they only provide short blocks beyond the externals.

I got it today and I did a thorough test.
It starts differently. You need to hold the throttle to get it started. It started easy using the instructions on the air filter.
It took about 5 minutes to get it to run full throttle. I used the tiller attachment and it did have plenty of power.
And there  are no adjustments for the fill throttle/ no adjustable jet.
The new bump head looks interesting. I will be checking this out in the spring.
The season is almost over here in Maryland.

What carburetor did they put on it?

Don't have a Ruixing Rotary on hand to look at here. Have check the top of the rotor section to see there is EPA plug you can remove? Or better yet post a image looking down top of the rotor where I can see down the center hole.

Goto https://smile.amazon.com/s/ref=nb_sb_ss_i_4_4?url=search-alias%3Daps&field-keywords=8+pcs+carburetor+adjustment+tool+kit&sprefix=8+pc%2Caps%2C178&crid=JH1D7NDYM9CD
to find an 8 pc set. Also includes the small D and the 4mm hex that on some of the newer Zama carbs.
 
I use Smile Amazon as I donate a portion of my purchases to charities.

MdStamen
Thank you! The one needed is shy of 3mm.

Actually the small Pac Man screw is about 1.78mm OD and the hole that the toll fit into is just under 3mm. I have ran into the small Pac Man yet but use the small Single D several times on the Echo Zama rotary carbs. Pulling that EPA plug is fairly easy once you got the extractor for it which is a 2.5 mm LH threaded but have had to the 3mm extractor a couple times too where operators and other tech try unsuccessfully to remove the plug.
 
I did throw away the large Pac Man that came with my set as my older Pac Man is much better made.

I am still waiting for the kit.
I installed the Amsoil oil at the 80 to one ratio with High test gas.
Believe me the problem left and the Ryobi runs excellent. I also tried this mixture on my Echo Pe and that runs like a new machine.
My son mentioned to me that must have tuned up the Ryobi and Echo.
If someone told me this I would not believe them.
I am still scratching my head.

I have the ry251ph trimmer. good low and mid but really sucks at the top end I'm trying to figure out if there is a compatible carb from walbro or zama. if anyone can figure it out or has an idea I would really appreciate it. part# 307160001 is the original.

I saw that but was curious if anyone had found a carb that would work. it drives me nuts they put all these controls on our stuff so we cannot work on them ourselves. I'll try the amsoil like you said.

I honestly never heard of amsoil sabre until I read your post. I'll get some and give it a shot.