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912ul soft start

in 912 / 914 Technical Questions 8 years ago

  • Re: 912ul soft start

    by » 8 years ago

    If you have soft start leave it. It makes it easier on the engine, gearbox and starter.
    Let's not call it rough running. How about pre timing change? :dry: :lol:

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

      
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  • Re: 912ul soft start

    by » 8 years ago

    Thanks again Roger for your advice. :)
      
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  • Re: 912ul soft start

    by » 8 years ago

    Hi Stephen

    If it is a standard 912ul, I would suggest you disconnect the soft start trigger wire. This will make it revert back to standard ignition as you know, but it will still be firing at 3 degrees ATDC and then going straight to 26 degrees BTDC. The old flywheel timing starts at 4 degrees BTDC and then moves to 26 degrees BTDC. This is less noticeable and less aggressive, but for a standard 912ul and not the 912uls, I think is better than the rough running for 6 to 8 seconds.

    I presume you don't have the slipper clutch fitted to to 912ul as it is not necessary and I would defiantly not recommend it. If you did want the added protection of the slipper clutch to protect your crankshaft, but don't need the 30 degrees of slip that is needed for the 912uls, but causes all the starting problems, then you could have fitted the dog that was used in the 912is when it was first launched, but has now been withdrawn. I think Rotax should do this as an option for the standard 912/914 and leave the 912s as it is. They must have them in stock.

    Our new 912ul Icarus C42 aircraft come with the modules wired for soft start and we disconnect them ASAP.

    Also, I think the length of time the modules stay on retarded ignition is a bit OTT. I would think 2 seconds maximum would be sufficient.

    Cheers Mark
    Thank you said by: Stephen Foreman
      
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  • Re: 912ul soft start

    by » 8 years ago

    Hi Mark, thanks for taking the time to reply to my question. I think your post is very interesting and I think I'm going to disconnect the soft start. Also I have now checked and adjusted the choke cables which had got out of adjustment over the last few hours and I think I'm going to re balance the carburetors hopefully by the time I've do this the engine will be starting as cleanly as my old 912ul did.

    Thanks again.
      
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  • Re: 912ul soft start

    by » 8 years ago

    The doghub from a 912iS is not compatible with a 80hp 912UL gears.
    Sever wear will result if you mix these two parts as the 912iS doghub has a 7 degree angle and the 912UL has a zero degree angle.
    See page 3 of pdf attached.
    widenarrowgearinfo.pdf (You do not have access to download this file.)
      
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