Can someone identify this bike for me please?

[nategs550]

The gas cap has a Yamaha logo on it. The only numbers I can find is M20 6501. I always stare at this and one day really want to grab it up. Google hasn't brought up anything for me.

 

[cosworth]

Yamaha YD1

 

[Redbird]

I'm gonna go with the YD3

 

[Tune-A-Fish]

YDS3 the speedo has been ripped from the headlamp and the tall bars??

 

[Redbird]

Thanks for adding the 'S' Tuna. It made me look a little deeper.
To further narrow it down...
http://www.realclassic.co.uk/yamaha_yds3_250.html
With the exposed fork springs and the high pipes, looks like it's a '66 YDS3C "Big Bear"

That's a fairly rare bike.

 

[Tune-A-Fish]

It's like catching a goldfish in the Atlantic