No, I'm no dealer, just someone trying to get more info out on these mowers, as there is basically none.
I had to pick one up as a backup to my JD 318 and did a lot of research. All tractors are basically the same, with some minor differences. These tractors probably have the least amount of info out there, but you can still get service manuals for them too.
A dealer actually runs this site and you can order parts from them... www.yamahagenuineparts.com
or www.canns-bilco.com or
http://www.powersportspro.com/pages/parts/viewbybrand/2/Yamaha.aspxor you can also substitute a NAPA Gold oil filter #1635.
Good luck with the surging problem. Doesn't have to be Seafoam, basically any gas additive that cleans up deposits will do. I have just had good luck with Seafoam, and have been using it for 25 years.
Rattosh51
YT6800