The lows are a pain to find when they're installed in the ski. They sort of hide behind the throttle lever. If you open the throttle, you may have better luck getting your fingers them.
You say you started it 6 times in a row. Was that after prolonged cranking to get it started the first time? If you pour a bit of fuel down the carb throats, does it fire right up? Do you get black goo dripping out of your exhaust pipe after you crank a while?
Judging by your recent comment about wet plugs, I wonder if your engine is not flooding. It's possible one or both of your carb needles are leaking and creating an overly rich condition. It takes a ton of cranking with the throttle wide open to clear out a flooded engine, and it'll drip black goo out the exhaust. If you pour fuel into the carbs, it'll have no effect.
On the other hand, if pouring fuel makes it fire up and you've experienced back-fires, you have a lean condition and are starving for fuel.