912 starting help

Discussion in 'Engines' started by Matthew Roung, Apr 20, 2017.

  1. Matthew Roung

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    The 912S in my bird has always started well in the warmer weather. When it got a bit cooler, pulling the engine through 10 or more blades with the electric fuel pump on and ignition off before trying to start worked fine. When it got cold? what a bugger......When it did start (after much cranking) it would shake and rattle no matter what I did with choke or throttle for several seconds until warming enough to smooth out. It shook so bad one time it popped out one of the header sockets from the muffler. That is just no good.
    Solutions? Many said service the sprag clutch. Others said need stronger battery or soft start modules. I did check the enrichment circuit just to make sure it was opening all the way, and it was. Battery seemed to spin it over just fine, but I have a booster pack waiting in the wings if necessary. So sprag clutch or soft start module? Others have had luck with these, while others still have cranky cold starting after spending the $$. Pre-heating of course would help (alot - previous owner never had cold starting probs but he always put the heat to it) but would not be practical for me. No electricity in my hanger and I would prefer not to use a propane or kerosene type heater, or have to lug out a generator and stomp around in the cold while the engine warms for an hour.
    Was thinking about the Subaru in my old plane, and how it would start quickly anytime every time no matter the temperature and........aha! Bingo.....That soobie had an automotive carb with an accelerator pump, and I always pumped the throttle a couple times to introduce some raw fuel into the manifold.
    So, I installed a plunger-type primer in my plane. Was told the Bing carbs have an injector port on them somewhere, but I couldn't find it. Was easy enough just to drill a hole in the end of the air filters (my engine has no airbox -individual filters on each carb) and slide in a tube to inject the fuel.
    It works perfectly. Couple squirts with the primer before cranking and it lights right off and settles into a smooth idle, cold out or not.
    So there you have it. Should you have a cranky starting 912, try installing a primer before spending the big bucks.
    I'm either going to find those ports on the carb and use 'em, or make new fittings where the balance tubes are on the manifold for the primer. But for now, the tube through the filters works fine.
    -Matt
     
  2. booger

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    that is quite interesting, good detective work, i have had 80 and 100 hp rotax but only once is a very long while does the new 100 ph start rough, even when 15 below, the old one, 2003, has not done that yet. take saturday June 17 off and come to quebec with us.
     

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