JB Weld has been used on zenoah transfer ports for years. The old 23 zens would have JB Weld added over the transfer ports and then extreme porting (right through the existing case) was done. Motors were very strong/fast. Saw one running recently that still gives mod 260's a run for their money. If the bond is not structural then certainly consider giving JB a try.
http://www.rcuniverse.com/forum/m_90...tm.htm#9100093
Welding might add the risk of distortion of case.