My 300Ex is leaking a little oil out a plastic piece on the top end of the motor. Its on the side with the rear brake lever and its just a little plastic circle on the top end of the motor. Its not a severe leak but makes it look like crap with oil on the top end. Does anyone know why its doing this or how to fix it? Also, how much more power can I expect when boring it .20 over and adding a high compression (11:1) wiseco piston? Thanks

 

I don't know why that it is leaking. I think that a 11:1 piston isn't that good of an idea. I have heard that the starter has problems turning it over. Maybe a 10.25:1 would be ok. You probably should feel a power difference.

 

The 'thing' that is leaking oil is a plug that, when the head is removed, allows access to the cam bolts. You will have to take off the head cover to replace/reseal the plug. Mine has leaked for a couple of years now and I just wash the motor with degreaser to clean it up. If yours leaks really bad you should replace it so as not to run the motor low on oil. If you get a Honda Factory Service Manual it will show you the procedure for replacement.