Hard starting Rotax 912 ULS

The fuel is fresh. But I think I might start using 50/50 mogas/avgas. Usually I only get avgas if I have to make a long trip and refuel.

Your carbs don't need an overhaul, just a quick inspection of the idle jet and float weight verification. A carb sync is quite easy. It takes me 15 minutes. Once you understand what you are looking at with gauges it's a piece of cake.

Charles,

If your mechanic is not checking the carburetor synchronization every year perhaps he doesn’t understand how to interpret the MML scheduled service checklist?  At the bottom of the checklist someone verifies the checks were performed per the checklist, carb synch being one of them, and documents completion in the engine log, and Returns the engine to Service. 

There have been a couple of comments which suggest people dont understand how to maintain the "quality" of unleaded (ULP) fuel.

When I flew LyCons, I was taught to refuel before putting the aircraft "to bed" . This was seen as the polite thing to do, for the next pilot but more importantly to reduce the impact of condensation in the fuel tanks/water in the fuel.

After converting to Rotax, I stopped doing this, preferring to refuel before first flight of the day. If the aircraft sits for a week or two between flights the remaining ULP in the tank will degrade - the easiest/quickest/cheapest way to "fix" this is to refuel with fresh ULP. The resultant "shandy" of old & new, will be almost up to fresh fuel standards.

In Australia the minimum standard for a Rotax 912ULS, is 95 RON - I use 98 RON, as this gives a buffer for both adulteration and aging BUT the 98 deteriorates faster than the 95 RON. The above "shandy" technique will restore most of the 98 attributes and be well above the minimum 95 RON standard.

ULP will remain fresh, at 75%+ full, in a sealed container, for well in excess of 6 months.

The results are in. As a pair both sets of carbs weight 6.6 grams. each was about 3.3 grams. Float bowls were clean.