This weekend I picked up a couple snowblowers off Craiglist, one of which was an Ariens SS522E with a Tecumseh 139cc 2 stroke. It ran a little rough, so I did a carb clean and reassembled. It was strange, because the carb appeared to be new. Upon starting back up, it still ran rough, but after a couple minutes of running, the RPMs began to skyrocket, like a runaway diesel. I pulled the ignition key out, and it continued to rev high for a few more seconds without ignition. I let it sit and tried to started it later and the second I turned off the choke the RPMs climbed again. I would hate to send this blower to a scrapyard, so if anyone has ideas that would be great.
Thanks!

I'd remove the carb and check for any MISSING gaskets between the carb, manifold and block.
 
Any air leaks will cause a lean condition with high RPMs..   I'd also check for any leaks between
the cylinder and block (and dark seepage- internal vacuum leak)...
 
 
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OK. Thanks for the advice. I inspected the block, and I noticed that the spark plug was loose and seepage formed around it. I tightened it, started the engine, and still high revving, backfiring and surging on choke and off choke. There also appears to be an exhaust leak on the muffler. I will try to add a video of the engine running. I am not very experienced in two strokes, so if any advice would help.

Does this engine have an adjustable / manual throttle the operator would adjust from 
the main handle?
 
Can you find any model #'s on the ENGINE itself and post them here?
 
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No, it does not have a manual throttle. I figured out it is not a governor related problem, because I bypassed the governor and made a manual throttle and still surging only on high throttle. Also it turns out the white "smoke" around the muffler was just steam due to rain the previous day. Still thick white exhaust, which is pretty confusing judging by the fact that it's surging. Model is HSK850-8310C. I also removed the carb, cleaned it again, and made SURE the gaskets were sealed tight with Permatex hardening sealant.

https://www.partstree.com/models/hsk850-8310c-tecumseh-engine/engine-parts-list-0/
 
W/O the homemade throttle set up, what is the engine RPMs? 
(Which would either be off or it's normal operating RPMs).
 
 
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