912 IS engine starts astero and vibrates a lot, then it works perfect

There have been a few reports of this phenomenon.
The next time you experience a "Hard Start",  quickly shut OFF One Lane.
Be sure to report which Lane you disabled and the results; Did it Stop or smooth out?

Thanks for answering, I have already tried to leave the pumps, both on for a minute, I have also tested with line A and line B, and nothing changes, I also tried with a bigger battery, what I noticed is that in the moment to start and until the engine starts it rotates at 300 rpm max and it seems very little to me, and verified other 912 is and also they do the same, my intention is to try a large carbureted rotax 912 starter and see if it turns faster and smoother startup.

Is the engine hard to start or are you talking about just 1 or 2 seconds of vibration as the engine first fires?  My 912iS also has this vibration when starting (and stopping) the engine, as do others I know of.  Its my understaing that this in inherent to the engine design and has to do with the different propeller hub that is required on this engine.  I typically advance the throttle quickly to 2000 RPM to minimize this. My aircraft is also a Bristell, and so far my exhaust sytem has been fine with 220 hours.  

Hi Jeff, always start the engine, vibrate for 1/2 second abruptly and then it works perfect, in my case it is installed with a fi-ti propeller, and I have seen other 912 is and they start in the same way, I am concerned about the health of the bench and long-term exhaust.

Many people who complain about this issue are not starting the engine with the throttle lever in the correct position. Rotax states to have the throttle lever at 1 to 2 CM from the closed position (55%-65%) The engine will actually start a little smoother if you have the throttle set to 70% and then reduce the throttle back to idle conditions (typically 2000 RPM)