I won't knock Volfy's recommendation either.
For one reason... Chainsaw are MUCH more powerful than the Weedies.
A typical 42-46cc poulan will push 25 lbs thrust at least... (20-22 inch prop)
My ryobi on a good day may get 16 lbs thrust....(18 inch prop)

In the Ryobi's defense though, I haven't had a problem with the throttle linkage on the rear carb...straight shot to the throttle arm with a ball link...or nylon nosewheel steering arm..
http://www.crazyherb.com/BigPink/Picture015.jpg

Whereas, with the Poulan 42cc, I had to buy a special "rotator" manifold to get a straight shot linkage to the throttle arm....not a problem...just another bolt-on part..

My next conversion, by the way, will more than likely be a Poulan 46.

I'm with Volfy heading to McDs to get my ice cream too....

Find your airframe (Stinger 1.20)......... they are equally easy to convert but slightly different applications...ryobi will fly it fine...
Poulan will YANK it through the sky...

You need to take probably 1.5-2 inches off the nose of the stinger to get it to balance right with either motor...

OH YA! Here's a link to a photo-by-photo conversion of a ryobi!!
http://www.geocities.com/CapeCanaver...071/ryobi2.htm

Good Luck!
CrazyHerb