Well, if it runs well with one carb, there is hope.
Compression test (it is simple and readily available) for over 100psi,
then leak test (because it is essential!) for the engine to hold 7-5 psi for over a minute.
Build your own leaktester or buy one but it is essential you do these two tests because these two MINIMUM parameters are essential to run and have power.
Leaks especially can really screw up jetting and engine operation and can be as destructive as bad jetting on pistons, cylinders and cranks.
Once those two minimum parameters are assured, then you have to check and adjust your jetting with a plug chop.
You start from the top with your main jet, down to your needle, the pilot and finally the adjustable idle mixture and speed screws.
A good starting point is whatever the working carb is running, but 2 times out of 3 just sticking a good working mystery carb on a 2 stroke will result in mechanical engine death. Bite the bullet, do the job right, it is cheaper in the long run. Borrow a compression tester, $25 of hardware store parts builds a leak tester, and $12 of spark plugs and an afternoon's work should get that engine running like a top. Not doing this will most likely cost you a $500 crank and piston rebuild, and well as many, many hours of sucky performance and futzing to get it to run.
Steve