Switch engines
 

In 2010, I struck a deer while riding my 2005 M50, wrecking the front end and writing off the bike. I replaced the bike the next year with a used 2005 CT50.
I like the latest bike very much indeed, but with 80,000 km on the clock, the engine is beginning to burn oil. I would like to switch the engine with that of the written off M50, which has only 20,000 km on the clock, and appears mint. Both bikes are stock Suzuki. Will I encounter any serious problems? Are there fixes?