What model Yamaha is this?

Can someone help me find out what model Yamaha 3-wheeler this is? I just got it yesterday I have not taken any photos of it yet because i got no batts for the cam yet. But here is the VIN and what it says on a sticker 1984 YAM21Y0123 and the VIN is 21Y-050634 when i get some photos i will post them. I would like to find out what it is because i never seen a 4-stroke with a oil tank and even a OIL pump and the motor mounted so far in the back.:confused

 

Maybe these will help had a friend take them with his phone and e-mail me them

http://img174.imageshack.us/img174/8462/0310081100ln1.jpg

http://img90.imageshack.us/img90/9592/0310081100aux8.jpg

http://img112.imageshack.us/img112/1447/0310081101ll4.jpg

 

Sorry...can't help...one too many wheels for me Looks an interesting project though!