Start then Stop

Resurrecting this thread.  I'm still plagued by this issue.  Now it takes 3-4 attempts before it will start and run without stopping.  Any new ideas out there?

I think you need to go back to the basics and make sure everything is as per the operators and installation manual. 

- Correct Voltage and battery size

- Correct throttle position during start-up (55-65% open)

- Make sure your installation incorporated the bypass line from the pressure side to the return side with a metered orifice. This helps prime the fuel system (see fuel system diagram in the 912iS installation manual) https://www.rotax-owner.com/pdf/IM_912_iSeries_ED2_R1.pdf

-Some Gascolators can act as an air trap based on their design and it takes time for your engine to purge the air out of the fuel system (if you don't have the bypass line)

- See if switching fuel makes a difference (auto, av-gas, swift)

If all the above checks out, I would take it into a Rotax Service center and have them look everything over. Someone who is proficient on the iS and understands it fully. 

Jim,  Have you solved this rough start/stall problem?

I am having the same issue.  No obvious problem found when Rotax reviewed my downloaded engine data.  Rotax wants me to remove gear box to see if excessive gear lash is causing the prop to vibrate during start.  My gearbox has under 300 hours so I just can't imagine that to be the problem.

Gear lash is easy to measure.  (Apologies for the mixed standards.)

The 100% wear limit is 0.20mm at the 4" Bolt Circle on the Prop Flange.
This means that you can have no more than 0.20mm of backlash at a 2" radius; or 0.10mm per inch.

Extrapolating out; and assuming that a 68" Prop has a 34" radius ...
That means you should measure no more than (0.10mm x 34 =) 3.4mm (0.134") of backlash at the Propeller Tip.

New parts will measure about half the Limits. (New does NOT equal Zero.)
So anywhere between 1/16 and 1/8" of Backlash at the Prop TIP would be OK.

Be sure to adjust the number for your actual prop Diameter/Radius.

Still an issue.  I've learned to live with it.