Exhaust system

Is this a Rotax exhaust system or one produced by the aircraft manufacturer?  What type of aircraft is it?

The exhaust joints being shaken out of place on the 912iS engine is not that uncommon and has been discussed on this forum before. Others have also used added springs and safety wire techniques to stop the exhaust joints from dislodging, typically at the muffler as you have seen.  

A big factor is how you start the engine.  As per the OM the engine starts best around 55% throttle.  Unless you have a throttle position readout on your EFIS it’s hard to know where that is because it’s not linear with the throttle lever position.  On the Garmin G3X you will see the (small) throttle position indicator in the upper left of the engine strip.  This indication goes away and becomes an ECO mode indicator once the engine is started. It is provided to aid in the starting procedure.  

I find my engine starts best cold at 60%, and some folks use settings as high as 85%.  There is no choke on the iS engine, but advancing the throttle commands the ECU to give a longer fuel pulse, so it has the same affect as a choke. If you have the throttle set correctly for a cold start, you should have to back off the throttle immediately upon starting to get the RPM down to 2100.  Experiment with different positions until your start smooths out.  It will never start completely smooth, but there are sweet spots which make a big difference.  Rotax provides a graph in the OM showing the starting behavior for different temps and throttle positions.  See attachment below. 

On my 912is sport I turn off the engine when achieving around 2250RPM. 

ALWAYS START SMOOTH. 

It’s on a Bristell aircraft. Which I now understand is not a Rotax muffler. I’ve been starting it probably closer to the 1cm on the throttle. I’ll try 2cm. Thanks.