912 ULS starting but stalls

Electric pump on for starting - Why? With the exception of a fuel vapour lock situaton, the pump ON for start has no benefit and marginally "sucks" some starting battery power.

and sometimes left on for flight.  - I use Backup/Boost Pump for all TO/Landings - have been known to forget to turn it off, until well into flight. Should not be required for sustained flight, unless fuel delivery problem.

Fast idle has always taken 3-4 seconds. How do I make it happen faster? - I don't know. perhaps one of our experts can get back to you on this

Four years old. Hobbs is 330.

Two 200 hour services on the carbs by Lockwood in the first two years. Plus one return after first service because the throttle would not close on one of the carbs. "There was a burr on it" No paperwork.  My last 912ULS, in whole or part, never went for service in 20+ years/900+ hrs. Why did your carburettors need this work? Could Lockwood have made an assembly/adjustment error?😈

Why did your carburettors need this work? Could Lockwood have made an assembly/adjustment error?

Could be. They mucked up one carb when servicing.  

I had corrosion in my bowls fitst time I looked at them.  And repeated clogging of idle jets with stalls while taxiing.  Lots of crud inside. 

Rotax and the aircraft manufacturer said (well no one from Rotax ever spoke to me) my fuel was the cause but I was using same fuel several others were using.  Also the same Lucas octane booster that loads of people here have used forever. What do I know?  Got nowhere. This all in the first two years. Used 100LL for a few months and went back to E-0 and Stabil with no problems till a year and a half ago. 

The battery is really good though not new.

So.

I will start with raising the idle a bit.

Then check the idle mixture screw for 1 1/2 turns out.

I could put a jumper on battery that is huge power and see what happens.

Or totally rebuild the carbs...ouch!  Or, Toss them and replace. triple ouch!

Pics are carb bits at 25 or so hours.  First 200hr service was at 54 hrs. 28 Jan. 2021.  Second on 3-5-2021, 67 hrs. 4.5 hrs later another 200hr serv.  Replaced carb bowls at 147 hrs. end of idle jet problems till Dec. 2022.  172 hrs.

It has always taken 3-4 seconds to raise idle, no matter the clogging idle jets.

The curtiss cup is the worst I have ever gotten from my tank.  After that, NEVER more than a pin head of anything except maybe two drops of water one time and a couple of black "grains".  I have pics of every sump check that was ever drawn that had anything visible.

But that is me just whining about fuel burnt flying under the bridge. 😒

Just before carb bowl replacement.

That's terrible Jeffrey.

Just wondering about the fuel additives that you are using "Lucas octane booster & Stabil" - What do you hope they are doing for your fuel/engine?😈

I believe that the Lucus Octane Booster effective ingredient is MMT (Methylcyclopentadienyl manganese tricarbonyl), about 5%, suspended in naphtha. It is marginally effective at doing what it says, but can cause fuel system and engine deposits. I would not use it in my aircraft engine.