that was my first thought, but i checked and double checked that ratio, the first 4 gallons of the same mix ran as usual. Normally i have a black carbon mark on the hull from exhaust, but this time oil was running out the exhaust. How does the oil make it to the exhaust as if it was never mixed in the first place?
Your ski looses a lot of fuel through the exhaust. Some fuel stays behind. That fuel then evaporates a leave a lot of oil residue sitting in the exhaust to run out later. This would not explain poor running.
There are also a lot of problems letting a ski sit. Your jets can be clogged, your needle and seat could be leaking, so forth.
I would start by checking the needle & seat. The best method is to use a mikuni pop-off gauge and ensure it is in spec. If you don't have one, you should consider buying 1, but at least visually inspect the needle. If the rubber tip is hard or grooved, it will be leaking fuel past the needle. This will cause your motor to run rich and loose a lot of fuel.
Throw in a new set of plugs, clean the carb, test the pop-off (or just replace the needle and seat), flush the fuel lines. Then retest.
In the future, always ad fuel satbilizer to the tank and run the ski on the hose long enough for that stabilized fuel to get to the carb. Also, if you are going to let the ski sit for a few month, use ethanol free fuels. I run 90/10 in my ski, but I ride 4 days a week. It doesn't hurt my ski, but if you let it sit, it will gum everything up w/o a doubt. I'd prefer ethanol free but it's not as readily available.
