The HiLo refers to the adjusting screws, which is which, high speed vs. low speed. The Lo will be the one closest to the cylinder. I believe the carb Id is on the opposite side of the carb?

If it's starting hard, and it has fuel to the carb, it's likely lean. If it hasn't run in a few days, drawing fuel into the carb can be a bear. I don't know what to tell you there. Mine has done that. When I was pretty frustrated one day, I put maybe half a teaspoon of fuel into the exhaust while holding the plane inverted, then rocked it to let the fuel into the cylinder to prime it. Worked like a charm...

Honestly, I'd have to guess it's not a Walbro, but would have to pull the cowl to see for sure. -Al