Ok so I made the mistake of offering a carb clean for a co-worker. Carb came off his modified '99 Yamaha Wolverine ATV. The bike was modded by a previous owner and has a 400cc big bore kit, hot cams and this mystery mikuni carb.
I can't find a part number of any sort of ID on the castings. It just says mikuni corp on a few spots and thats it. It seems like a dedicated dirt carb, since the linkage and what not have snazy plastic dust covers.
That is an odd one, at least as far as the dirt bike carbs I've seen over the years, but those were all two strokes. They always had the throttle cable at the top to pull up the spring-loaded slide and needle.
His bike is a '99, not sure why they swapped it out but anyway this puts me in the right direction to find a parts list and break down. Basically I just need to find a float and maybe a few other bits.
Picked up the new float and finished the carb clean & overhaul tonight. Overall it cleaned up pretty good, which is amazing since the poor thing had been neglected hardcore and beaten and abused by some previous attempts at servicing. Should be reinstalled and running for the long weekend.