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Thread: Dual STI build log

  1. #591
    Senior Member PapuaPilot's Avatar
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    Nov 2013
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    Nampa, Idaho
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    921

    Default Re: Dual STI build log

    Johnson Creek is a beautiful place. Good thing you did it last week, now the smoke and visibility is really bad and there is TFR for fire fighting just a mile south of JC.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

  2. #592
    Senior Member
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    wales,ny
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    527

    Default Re: Dual STI build log

    Dustin, the first long cross country is where that fuel imbalance issue surfaces , and I went thru the exact same issues as you years ago when I finished my Series 5 and started venturing further from home base. It is a bit disconcerting watching that fuel drain exclusively from one tank , and I used to slip to balance it but that wasn't very efficient. After a few flights like this I finally added fuel shutoff valves between the main and header tanks on both down lines. Problem solved . Added benefits are : maintenance isolation and ability to keep fuel from " peeing" out low tank vent when parked on sloping terrain and ramps. There a thread somewhere on the forum that addresses this issue. Bruce N199CL

  3. #593
    Senior Member
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    Dec 2017
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    Mapleton,UT
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    717

    Default Re: Dual STI build log

    Yeah we are glad we got in when we did because the wind shifted and it got pretty smokey. In fact my plane still smells like smoke, so I am going to go "air" it out today.

    Thanks Bruce. I think I found your thread. I may go that route. For 120 hours it has balanced correctly and I have done multiple long cross countries and had no issues, so I am on the hunt to find what has changed.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  4. #594
    Senior Member jiott's Avatar
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    Portland, OR
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    2,458

    Default Re: Dual STI build log

    Get the good Mercedes fuel cap gaskets and then quit worrying about it. In nearly 900 hours I have never had the engine even hiccup even though the fuel level has disappeared from one sight gauge many times. I have never heard of anyone having an engine stoppage due to this issue as long as there was fuel in one tank. Don't you think Kitfox would have addressed this issue long ago if there was any possibility of a safety concern? Just my opinion FWIW.

    I had a stupid experience 5 or 6 years ago when I stupidly left the gas cap off one side and went flying, with a passenger! The slipstream generated a negative pressure in that tank and sucked all the fuel out of the opposite tank into that tank where it was slowly being ejected out of that open cap. The engine never hiccupped and fortunately I noticed the abnormal reduction of fuel level and landed at a nearby airport. Could not find a new cap that fit so I refilled with fuel and made a temporary cap and vent with good old duct tape. Flew home and found the missing cap near the hangar. From this experience I am convinced that even a severely leaking fuel cap gasket will not cause engine stoppage until ALL the fuel is gone from both tanks, but you WILL notice a drastic fuel imbalance on the sight gauges.

    Since this is perceived as a safety critical life-and-death matter, each of us must make our own decisions that we feel comfortable with. I am just relating my own thinking and experiences. I would not criticize those who choose to add the extra complexity of individual shut-off valves and then continually twiddle with them in flight; I admit they can be very handy doing maintenance on the fuel system.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  5. #595
    Senior Member
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    Dec 2017
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    Mapleton,UT
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    Default Re: Dual STI build log

    Thanks for the info. I will put the new gaskets on and give them a try and let you know.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  6. #596
    Senior Member efwd's Avatar
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    Jun 2015
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    Yorba Linda, CA
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    Default Re: Dual STI build log

    I have lost my fuel cap as well. I was just repositioning from one fuel supplier to another since the first had inoperative pumps. I noticed it missing when I arrived at the next pump on the other side of the airport. I always place my caps in the pilot seat from that point on. I have replaced my gaskets with the Mercedes ones as DF4 suggests. I continue to have some imbalance develop but I seem to be able to rectify it by slipping. I think I have one vent tube that is slightly out of alignment with the relative wind compared to the other. I no longer worry about it.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  7. #597
    Senior Member
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    Dec 2017
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    Mapleton,UT
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    717

    Default Re: Dual STI build log

    The STI wing is a little different animal IMO. 1/4 tank imbalance is normal, but venting fuel out one tank while the other is empty is not normal and does raise some concern. Especially when you have no airports in sight and no safe landing places. In my situation I think my engine will quit with one tank full and one empty. Donít really want to find out. Slipping just makes it worse or does not help. Yes kitfox is aware and they have seen it before. I am hoping new gaskets takes care of it. Seemed to happens after sub zero flights and I think the gasket became more rigid and did not seal. Defiantly going to test it locally before venturing out more then 2 hour flight.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  8. #598
    Senior Member
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    Dec 2017
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    Mapleton,UT
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    717

    Default Re: Dual STI build log

    I ordered the mercedes gaskets and I think they are going to fix the problem of the fuel imbalance...fingers crossed. The rubber seems more pliable which I think will help when they get cold. Seems to be the same thinkness but I did not measure. Went flying today, but flight was not long enough to tell. I need to fill it full of fuel and go fly for at least an hour to be able to tell if its draining correctly. One of the airports I want to hit next time in Idaho is mile high. I have been practicing uphill landings to get ready. Today I tried to land a new direction of a place I have landed at before. Its a downhill angled landing and its was pretty challenging getting it on. Took 4 tries to get in on. Two low passes with go arounds and then I rolled it because I was fast. Fourth attempt it felt good so I dumped the flaps and got on the brakes. Not a lot of usable runway before it drops off, so getting stopped quick is key. I then tookoff down the hill and decided to practice landing uphill. Running power on uphill landings is key so you don't run out of airspeed.

    Update on Cory's plane is we did an oil change as he has 50 hours on the engine. Mag plug was clean but still has aluminum in the filter. (It had some at 5 hours and 25 hours) Oil analysis is also showing high aluminum count also. Fortunately both engines, his and mine, are consistently the same, but does have us concerned. We are going to keep monitoring and see what we can find. I am 1 hour away from hitting 150 hours, and I will do and oil change and compare.

    https://www.amazon.com/Mercedes-sele...0725393&sr=8-2







    Last edited by Shadowrider; Yesterday at 04:19 PM.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  9. #599
    Senior Member jrevens's Avatar
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    Aug 2009
    Location
    Arvada, CO
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    1,695

    Default Re: Dual STI build log

    Wow, the price of those gaskets has really gone up. When I bought a couple of them from a local Mercedes dealer several years ago they were about $5.00 each. They are a little thicker than the ones that came with my kit.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE

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