Has anyone identified the cause of this? I've removed the carbs but need to go deeper.

not good

 

Maybe that little cover in the top-left of your photo. It has a seal that might have gone missing.

 

Found it! The source of the leak is from the cylinder base gasket where the U shape is for the cam chain.


Here's a few pix of the leak from different angles.




I don't think it will be getting fixed other than to clean it up again and apply some silicone sealant to the area with my big fat finger. Getting quick at R&R carbs.

 

Dropping the donk out and stripping it down to replace that gasket is quite labour intensive, not to mention the availability of other parts that may need replacing in the process.

Honda special tool 07954-2830000 Ring Compressor x 2 is needed to get the cyl block back over the pistons. Apparently there's no chamfer at the base of the bores to allow the rings to compress as the block is gently lowered over the pistons, like many other Honda models have.


If some silastic don't fix it a few bits of rag temporarily stuffed into that valley (shown in the first post) where the oil drips out from should stop it enuff to pass an inspection.