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Hard start 100 HP 912

in 912 / 914 Technical Questions 13 years ago

  • Re: Hard start 100 HP 912

    by » 13 years ago

    Hi All,

    There is nothing wrong with the Soft Start module and yes they beat Rotax to market, but the new Rotax soft start ignition modules do make a big difference and if you can afford them are worth the money. That said there are 20 years worth of 912's out there without soft start modules and they are running well.
    Another common issue is people don't do 100 hr. checks like they should and they don't do the friction torque check on the gearbox and it's so easy to do. If your engine kicks back then you should check the gearbox torque. Yes other things may cause this and they have to be ruled out first. Even though you might see in the 320-350 in/lbs and it is within tolerance it would be advisable to go ahead and replace the Belleville washers and re-shim. The max is 540 in/lbs. The higher the better. From all the gearboxes I check normal friction torque is 450-490 in/lbs. Many times increasing the washer tension to raise the torque value helps get rid of kick back, providing you have ruled out other causes.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: Hard start 100 HP 912

    by » 13 years ago

    There are 20 years of Rotax 912's out there but kickback was never a problem on the 80hp's. Kickback didn't come up until the 912S 100hp with the high compression was introduced.

    I don't have the figures in front of me but my friction torque was right in the middle of the min/max inch lbs for the setting. Nowhere did it say or would anyone with Rotax tell me to set the friction torque right at the maximum. That is until about 2 years ago with lots of folks having kickback Rotax came out with info that the gearboxes should be pulled and the friction torque set near the max allowed inch lbs. This was after I had done everything under the sun including rubbing chicken bones on the ignition wires to eliminate the kickback. Then put the Soft start on and it has never kicked back again, ever. I am soon due to send my gearbox in for service and will have them increase the friction torque. But, I will leave the Soft Start on.

    Rotax had a problem and as far as I can tell ignored it until the guys in England Conair came up with the Soft Start for a lousy $200. I spent $800 on the sprague parts needlessly because I was told that all that kicking back had damaged the sprague system. Now Rotax has new ignition modules and I should put them on, what do they cost $1200.00 each. Where does all this end? Rotax prices are absolutely obscene. Don't tell me it is because of liability issues, Rotax is so insulated from liability, I would guess they have never been sued.

    I still believe I have the best engine out there and hope that Rotax reads these forums and realizes that when folks have a problem with their engines, they need to seriously make an effort to find solutions. It is extremely difficult to solve these things on our own. I don't know of anyone looking for Rotax to foot the bills for solutions. Pilots are a very generous bunch and most are willing to pay their way.

    Dale

    Dale
      
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  • Re: Hard start 100 HP 912

    by » 13 years ago

    Guys, your starting to rant and lose sight of the "many" reasons you could be experiencing kick back! Yes the higher compression of the 912ULS is the primary issue that needs to be adequately controlled from "day one" of first use by following exactly the maintenance points Rodger Lee has suggested! That said, these good practices can't always totally eliminate other contributing factors out of Rotax's control which can ultimately damage or prematurely wear engine parts.

    For example, many people like to adjust their idle speeds too low to reduce landing approach speeds or to lower their float plane taxi speeds to name just a few. This causes premature wear of the gear box bevel washers leading to increased kick back issues as Rodger describes. Also things like prop blade tip flex, engine mount stiffness, moment and arm influences of external accessories like mufflers, oil and rad coolers, air boxes etc. all play a roll in the rotational forces that oppose those of the higher compression 912ULS. Rotax can't possibly control all factors, and they shouldn't be condemned when they come up with improvements that narrow such influences down!

    More horse power in any application usually means more maintenance, that's a fact of life. If you want less headache go to the lower power of the standard 912 80hp, if you want the extra jam of the 912ULS, the trade off is a little more maintenance, such is life!
      
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  • Re: Hard start 100 HP 912

    by » 13 years ago

    What Ralph said. :) I agree.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: Hard start 100 HP 912

    by » 13 years ago

    Maintenance and durability are two different things and we must separate them in this discussion.
    My plane and engine has been maintenenced by the book, but still there has been problems popping up. First the gearbox failed. It was fixed by installing a slipper clutch. Then the standard starter proved to be to weak. Rotax launched the heavy duty starter to fix the problem. Then the engine started to kick back on startup. And Rotax launched the new freewheel with later ignition. Now they also have launched new electronic ignition modules to fix the same problem.
    The starter, freewheel and ignition modules must be payed by the customers and they are VERY expensive. And on top of this comes expences with damaged sprag clutch and work.

    Maintenance is OK. We do the best we can because our lives depend on it. But to me there are a lot of issues that in my opinion relate to the engine construction. This should be Rotax's concern. I'm afraid bad reputation is developing in the market.
      
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