Engine Starting Problem

With removed engine it is easier to check complete ignition system. We did spark test but we did not find any spark. Rotation of crank shaft was very difficult even with removal of all spark plugs. Kindly tell me further checks / steps to troubleshoot exact problem

The crankshaft should rotate easily using the starter motor with a plug removed from each cylinder. If the engine does not reach a minimum cranking speed the ignition will not generate any spark.

If you don't mind me saying, you might be better off finding someone local to you who has experience of working on Rotax engines. It is very difficult to remotely diagnose faults on an internet forum. Somethings only become obvious when you are stood in front of the engine. You could post a video on youtube and post a link to it here. We may be able to make further suggestions.

You should have been able to check for spark with the engine installed, I don't understand why it had to be removed. Again, a video may make these things obvious to us.

Have the rotax  912 had problems for a year which developed into almost never been able to start, checked everything you did it was ignition modules , packing with ice worked for a while , once the engine was heated up and started there was no problem starting anytime the rest of the day ! It was Ultimately lack of proper rpm not quite being enough to make the plugs fire.

I’m not sure what the number was but it takes a certain rpm to make those plugs fire on these engines anything slightly less and multiple attempts of cranking weakens  the battery ( no start)

sent off to California power systems to have  them checked those modules have two sides to them! start side and a run side, the start side is usually the one that goes bad ( start side was bad on both modules )  I changed my modules with the rotax and and also put the soft start on there it’s been flawless starts every time perfect, I looked at all the other alternatives including the carmo  option , came down to it I didn’t want something rebuilt I wanted new parts so I opted for the proper parts with the additional soft start feature which retards RPM for the start side on the module which further helps it start if rpm does not quite meet the requirements,

I spent 1000 each it was worth getting the proper parts in the end! Two years 200 hours later everything is perfect! 

What is the S/N of your engine?

We had teh same problem with our 914F4. Finally both ignition modules were dead.