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Rotax 912ULS continue with starting issues

PostPosted: Wed Apr 26, 2017 9:41 am
by scubarider2
Ok, I know that Rotax has had starting issues for some time especially in the cold. So I ordered the Soft Start Module. Put it on the plane. The ONLY time that it actually helps without the kickback is when it is hot after flying it. First start is always so rough. It works perfect after it warms, I shut it down and then start it again. Works like a charm. Any advice on how to start this darn thing without it feeling like the engine is going to kick itself off the frame? In the winter months I do pre-heat and that helps some but the module still does not work the way it is supposed to. Very frustrating after spending that kind of money.
Dennis

Re: Rotax 912ULS continue with starting issues

PostPosted: Wed Apr 26, 2017 9:14 pm
by AV8R Paul
Get a Reiff oil tank heater and a block heater, that will solve you hard start problem. I had a Cell Phone Switch, that I could call and it would turn on the heater, before I left home. Sat had a cup of coffee and when I got to the Airport it was nice and warm. The cell phone switch was a SwitchBox (Don't buy a SwitchBox). I had it upgraded to a 4G cell phone, and after spending the money to upgrade it it doesn't work. I tried working with SwitchBox, when the Ass told me I wasn't using it right he said I was dialing the number wrong. Since I've had the problem with the Piece of Garbage SwitchBox, I started driving to the airport, plug it in, go have breakfast a IHOP and then go flying.

Re: Rotax 912ULS continue with starting issues

PostPosted: Thu Apr 27, 2017 8:39 am
by carpat
Hi Scuba,
First, let me apologize for my limited English. It is not perfect. With that said, I'll explain what I experienced with my Highlander powered by a Rotax 912S as well. A couple of years ago I started to have some issues starting my engine. It was cranking over and over and was very hard to start even in warm weather. Once started, it was shaking badly for a moment and after it was running smooth. Then it started to do some kickback on start up more and more, harder and harder. That was happening on the first start of the day. After, it was a lot easier to start. On the first start of the day, I was like you are and almost afraid to break something.

It cost me a lot of money as I decided to bring the engine to my Rotax approved mechanic. He pulled the engine off my plane and we investigate deeply to understand what was going wrong. Finally, to make a long story short. It appeared that I had one faulty float on one carb. The float was 1gr heavier and was sinking causing the carb to flood while the aircraft was resting. So the first start up was always rough. Then, with an engine hard to start for so long, that broke the sprag clutch causing the bad kickbacks. As I didn't built my Highlander, there were no fuel return line installed on my fuel system. So we installed a return line to help.

Here's the conclusion, having no fuel return line the fuel was forced thru carbs. One carb had a bad float so that carb was flooding and the engine was very hard to start. To many hard start caused a faulty sprag clutch. Having all that fixed, I can tell you that I should have done it fixed a long time ago. Now my engine is so nice and easy to start. I simply can't believe it. It is so smooth. Now I don't have any worries anymore when it's time to start the engine even in cold weather or not.

Hope my experience may help others,

Pat

Re: Rotax 912ULS continue with starting issues

PostPosted: Thu Apr 27, 2017 8:57 am
by FlyerChief
Hi Dennis,
There's a pretty good chance your problem is the Sprag clutch. Here are a couple of videos to check out. My buddy in the blue and white Kitfox in the first video had the same problem, but eventually had the Sprag clutch replaced and it starts like a new engine now. The second video explains a bit more about the function of the Sprag clutch. If you know a good Rotax tech, just have a chat with him about the issues you have and whether he agrees it's the Sprag clutch or not, but I suspect that's your problem.
Good Luck,
Dan
https://www.youtube.com/watch?v=oAJDDcCpvqQ
https://www.youtube.com/watch?v=tmmCm8KAdM0

Re: Rotax 912ULS continue with starting issues

PostPosted: Thu Apr 27, 2017 10:24 pm
by carpat
Dan is right, as I said in my previous post it is sure that you have a faulty sprag clutch. I don't know how many hours your engine has but Rotax definitely has a major problem with this part. They still denies it even with numerous users reporting it on many forums. It seems to happen as early as 200 - 300 hours. That doesn't make any sense. They denies it but changed their ignition system to retard the firing up and redesign the sprag. They didn't expect it when they put higher compression ratio on 912S. That thing rarely happen on the 912 and 914.
Pat

Re: Rotax 912ULS continue with starting issues

PostPosted: Fri Apr 28, 2017 1:57 pm
by AV8R Paul
It had float problems prior to my spray clutch going out at 423 hours.

Re: Rotax 912ULS continue with starting issues

PostPosted: Sun Apr 30, 2017 1:49 pm
by Av8r3400
Without a more detailed description of what the motor is or is not doing everything here is just speculation.

There is nothing wrong with the sprag clutch design. There are tens of thousands of them working just fine. There is a comparative few with problems usually stemming from lack of sufficient starter energy. (weak battery, small cables, long cable run, etc.)

Re: Rotax 912ULS continue with starting issues

PostPosted: Tue May 02, 2017 1:56 pm
by scubarider2
Thanks everyone for your thoughts. Looks like it may be time for some major work, engine removal, rubber replaced, sprag clutch, etc etc etc... Just money right? :mrgreen:
Dennis

Re: Rotax 912ULS continue with starting issues

PostPosted: Tue May 02, 2017 11:26 pm
by john2
scubarider2 wrote:Thanks everyone for your thoughts. Looks like it may be time for some major work, engine removal, rubber replaced, sprag clutch, etc etc etc... Just money right? :mrgreen:
Dennis


Dennis,
Can't take it with you when you leave this world so might as well get rid of it while your here :D

Re: Rotax 912ULS continue with starting issues

PostPosted: Wed May 03, 2017 12:09 am
by AV8R Paul
I look at it like this, if I can spend the money on something I feel is important to me, that is better than my Daughter inheriting it and spending on something I know I wouldn't approve of.

Re: Rotax 912ULS continue with starting issues

PostPosted: Wed May 03, 2017 7:12 am
by danerazz
Paul Z wrote:I look at it like this, if I can spend the money on something I feel is important to me, that is better than my Daughter inheriting it and spending on something I know I wouldn't approve of.


I agree, like college :shock:

Re: Rotax 912ULS continue with starting issues

PostPosted: Wed May 03, 2017 9:38 am
by scubarider2
:D :mrgreen: :D
Soooooooooooooo TRUE!