Anyone guess whats this is off?

[pop]

My TY175 definately only had 1 front bolt, I can remember trying to drill it to get it out.

[Bully fanatic]

Hello all. Maybe it is a specially designed TY one so the owner of the bike it is on can practice his or her flying W`s when going fast over knotted logs. Graham.

[David Lahey]

I think Graham has a good point there. It is not likely to be from a trials bike because the drainage holes would cause it to grip on logs. As well as that, the big hole is so big it would not give protection on pointy rocks. My money is that it is from an enduro bike, and with that single front mounting location, I reckon it is from a bike with a single front downtube.
I've got an idea why that big hole is so big. Maybe it is from a bike with a 4 stroke motor and the big hole is to access the oil filter or strainer. My 1970s 4 stroke enduro bike bashplate is like that where the strainer cover is.