I have an MVVS 1.50 and i crashed it.

The muffler bolt's striped out and i want to re weld them. However the engine is greasier than McDonald's. How do i clean it? One dilemma is that the outside part of the engine is all one piece and i can't take it apart in sections. The casing of the engine is all one piece and it need's to be cleaned. I have a solvent tank at work, can I use that?
-Foxtrot