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Author Topic: Why? (update)  (Read 2944 times)

Dwayne

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Why? (update)
« on: August 05, 2015, 01:24:57 PM »
This is a La 46, uniflow clunk that most times runs great, but once in a while it does this and I don't know why. I stop it let it cool and it will start normal again, very strange.

« Last Edit: August 06, 2015, 03:30:54 PM by Dwayne Donnelly »
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Offline Gerald Arana

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Re: Why?
« Reply #1 on: August 05, 2015, 03:10:11 PM »
Sounds to lean to me. What oil content are you running?

Cheers, Jerry
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Offline Steve Helmick

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Re: Why?
« Reply #2 on: August 05, 2015, 11:25:08 PM »
Dunno...but I was wondering what if you stopped it but didn't let it cool? Also was thinking about that clunk tank. You don't store it or transport it nose down, do you? Da Dirt reported having the clunk do a 180 deg. turn inside the tank when he did that...it might do something strange.  ??? Steve
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Dwayne

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Re: Why? (update)
« Reply #3 on: August 06, 2015, 03:35:11 PM »
 I removed the nva, venturi and  gave em a good cleaning, resealed them   , flew 5 flights today with out issue, hopefully that fixed it.
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Offline Steve Helmick

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Re: Why? (update)
« Reply #4 on: August 07, 2015, 03:25:25 PM »
Since it's was fixed by cleaning the spraybar out and resealing the venturi install, can we now figure out what was specifically wrong?

I'd guess that maybe there was a flap of sealant around the venturi that allowed a vacuum leak-on/off/on/off, or something in the spraybar or fuel filter that did something similar. You didn't mention a fuel filter. You use one between tank and spraybar?

You might put a filter (the plastic Master Airscrew one) on the uniflow intake, or route a hose into the backplate cavity, or plug into muffler pressure, to prevent stuff from getting into the tank via the uniflow vent.  

Can you have better filtering of your fuel? I see guys using syringes doing things that make me cringe...like remove the cap of a gallon jug/can on a misty day and pull fuel into the syringe through a filter in a hose and then flush the filter right into the tank....then lay the syringe on the dirty pavement. What sort of fueling method do you use? Do you usually use silicon seal on the venturi & spraybar? Did you put a new O-ring on the venturi?  Stuff like that!??  H^^ Steve
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"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Dwayne

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Re: Why? (update)
« Reply #5 on: August 07, 2015, 07:18:04 PM »
Quote from: Steve Helmick on August 07, 2015, 03:25:25 PM
Since it's was fixed by cleaning the spraybar out and resealing the venturi install, can we now figure out what was specifically wrong?

I'd guess that maybe there was a flap of sealant around the venturi that allowed a vacuum leak-on/off/on/off, or something in the spraybar or fuel filter that did something similar. You didn't mention a fuel filter. You use one between tank and spraybar?

You might put a filter (the plastic Master Airscrew one) on the uniflow intake, or route a hose into the backplate cavity, or plug into muffler pressure, to prevent stuff from getting into the tank via the uniflow vent.  

Can you have better filtering of your fuel? I see guys using syringes doing things that make me cringe...like remove the cap of a gallon jug/can on a misty day and pull fuel into the syringe through a filter in a hose and then flush the filter right into the tank....then lay the syringe on the dirty pavement. What sort of fueling method do you use? Do you usually use silicon seal on the venturi & spraybar? Did you put a new O-ring on the venturi?  Stuff like that!??  H^^ Steve

I've bin guilty of everything in your last paragraph at least once...lol Now I have two filters on a jug of fuel, one in the jug and one on the hose used to fill the syringe but not in the plane, I really should put one in. When putting fuel back in the jug I remove the lid so as not to contaminate the filters. Yes I seal the venturi and spray bar with silicon but no O-ring. I'm thinking you are right there was an intermittent air leak as it didn't happen all the time. I do use pressure off the muffler so the system is well sealed now and running like a champ, I really like this engine to bad they don't make it anymore.
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