One mans TRASH in as another mans GOLDMINE!!!
But seriously - I would keep the original carb.
Go buy yourself some KREEN from www.kanolabs.com
or some other carbon dissolver fluid.
Pour it in the oil and the gas and run it for a few minutes. It can clear out all the "crap" in the lines and the orifices.
Also, you can try some WD-40 or KROIL (see above) that works just great on rusted parts. I was able to remove /by hand/ a fully rusted on bolt when before I tried with a wrench after using KROIL.
Then at least you can ADJUST things on it instead of that junk plastic version. Then you will have yourself a good unit there!!
BTW: I am not advertising nor am I associated with Kano Labs, but their stuff is the BEST on the market that I found - it WORKS!!
I had an 15+ year old Craftsman lawnmower that just stopped workign one day. I poured in some Kreen and the next time I started it just came to dead stop. Hmmm... I took off the head and surprise: a big solid block of carbon deposit jammed between the cylinder head and the piston. I took that out (obviously loosened by the Kreen) and put it together - it is still working for someone to whom I sold it!!!!
I am giving this info becasuse lots of floks just trhow away stuff because they cannot FIX motors or rusted on stuff...with this stuff I am amazed at how well it penetrates and works. Good luck and happy "trashing"