Hey i have a 1985 js550 that is in need of TLC. I have been putting it off for awhile but its time. I rebuild the carb recently and it still leaked and never ran right. I was thinking about just starting fresh with a brand new one. Which one works the best? Which mikuni is the stock one for this model? I took the motor out and i am tearing it down and replacing almost everything. There is lots of scale and sand build up in the coolant passages. anybody know what works best to remove this? Also the head gasket and other gaskets seem to be blocking a large portion of the coolant ports. Is this normal? Any help is greatly appreciated.