The same thing happened to gsxr with a new head which IIRC he attributed to a wrong or poor quality valve stem seal.





If so, a new valve stem seal might do it for you. Trouble is, you need a funky valve spring compressor to get to the valve stem seal and I don't think anyone in the tools forum rents such a tool (go check). Maybe Perf Products rents it. Or maybe you can configure a similar watercooled VW tool.

[Edit] - Oops, photos courtesy of gsxr.

Sixto
87 300D