I have a 15 year old Ferris IS1500z mower with the Kawasaki FH641V-BS25-R engine. The engine has 986 hours on it and developed multiple oil leaks early this season. I replaced the upper seal, lower seal, governor shaft seal and installed the new breather kit which contained the cover, new improved gasket and breather valve. After assembly the engine started quickly and ran fine, most importantly no oil leaks. Over the course of a couple of weeks I put 6 + hours on the mower with no issues. Then after the mower was parked for several days when I tried to start it gray/white smoke poured out and it wouldn't stay running. When I removed the valve covers to see if I had a valve issue, I had a mixture of mostly gas with some oil pour out of both cyl heads. I would estimate 4 to 6 ounces in each. The rocker arms and pushrods all seem fine. Any help with this issue will be greatly appreciated. Also if anyone has a recommendation on an engine replacement, Kawasaki, Briggs or Kohler that will work in the IS1500z it would also be appreciated. Thanks in advance.