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I was giving another CFI a back seat checkout in my Rans S-7 with 914 when the engine failed at ~100 on final.  I landed and tried twice to restart the engine, soon noticing the pool of gas under the engine cowl coming from the airbox drains.  This had happened 3-4 flt hours previously, but on the ground and just before starting the engine, right after the 100 hr inspection.  At that time I reseated the float bowls and the flooding into the airbox stopped.  I then flew it for 3-4 hrs.  With this recent failure inflight, I once again removed the float bowls and observed the float pins were indeed splayed outwards, something I was not previously concerned about.  (My float weights are within limits at 5.9 and 6.0 grams as of 3-4 flt hrs ago.)  So my float bowls do seem to be distorted due to excessive bolt torque and possibly the retainer clip/bale that I've used.  Since I couldn't reshape the bowls to re-align the float pins, I manually forced the pins inward to near parallel with each other (basically about 1 mm each at the tops).  They are still very secure.  I reattached the bowls with 3 ft-lbs of torque, safety wired them, and re-attached the drip trays.  I left the clips/bales off.  I then did some ground engine runs and flew it overhead the runway for .7 hrs and all seems OK as of yesterday.  My dilema is in the advice provided by two very reliable sources.  One source stated that the bowl retainer clip is not used on the 914 and the parts diagrams confirm this.  However it is used on the 912, which I don't understand.  But also, the other source states that I should back the bowl bolt torque off to 2 ft-lbs, but then use the retainer clips to ensure a good seal.  Which advice is best and why is the retainer clip not recommended nor in the 914 carb parts diagrams?

Thanks

  • Re: 914 Flooding/Failure and Float Bowl Concerns

    by » 2 weeks ago


    The maintenance manual heavy (MMH) states the torque is 49 inch pounds or 5.5Nm

    There is also some advice on checking the floats are free and clear.

    I would be inclined to replace the float bowls (as they are distorted and likely to not seal properlly wich will effect your mixture greatly) and overhaul the carbs in accordance with the manual.


  • Re: 914 Flooding/Failure and Float Bowl Concerns

    by » 2 weeks ago


    Thanks Murray.  I'm aware of all that.  I've used minimal torque as directed by the MMH, but added the retainer clip after having a float bowl seal problem in flight that lead to a power loss.  I also included new rubber seals at that time (4-500 hrs ago).  Lockwood recommends ~35 in-lbs, so the MMH setting appears to be too much.  I called them Monday morning; they are one of my two very reliable sources mentioned above, but I neglected to ask why they don't recommend the retainer clip on 914s.  I rebuilt the carbs about 200 hrs ago.  I've had no problems until now.  The float bowls are expensive.  Also, I have no confidence they will be any better.  Mine seal quite well, with or without the retainer clip.  My dilemma is that I have another very reliable source that recommends 2 ft-lbs or less, but includes the retainer clip.  So for anyone with significant float bowl caused flooding experience, which advice is best and why is the retainer clip not recommended for the 914, nor included in the 914 carb parts diagrams?


  • Re: 914 Flooding/Failure and Float Bowl Concerns

    by » 2 weeks ago


    Hi George

    The 914 has pressure in the float bowls, not just ambient.  They are pressurized to the same as the airbox.  The wire retainer is suitable for the normal atmospheric pressure on the non-turbo but not recommended on the turbo version.  The 914 type have an O-ring in the cap/bolt that you torque.  It has to be safety wired after installing.  I believe that the 35 in lbs is sufficient as long as you safety wire them.  Once the bowl is bent you have to replace them.  The nut will pull up too far into the main jet and you can lose power at full throttle take-off with the fuel restriction caused by the lack of correct clearance caused by a bent bowl.  The float pins being bent outwards is a sure sign of that problem.  

    Cheers


    Thank you said by: George Sousa

  • Re: 914 Flooding/Failure and Float Bowl Concerns

    by » 2 weeks ago


    Thank you for that response.  One of my sources also warned me about the nut pulling too far up into the main jet.  That's probably why he recommends 24 in-lbs.  But I'm a little fuzzy about not using the retainer clip on a float bowl that would have more pressure (the 914).  That seems like a compelling reason to actually use it.  


  • Re: 914 Flooding/Failure and Float Bowl Concerns

    by » Yesterday


    Hello George

    The 914 is used with a retaining nut rather than just the clip. This is because you have a boosted pressure engine, not just atmospheric air in the chamber.  

    Cheers


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