Tuning a Zenith 14992 Carb on a 1/2 VW

Discussion in 'Half VW' started by Dee, Dec 6, 2018.

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  1. Dec 12, 2018 #41

    N8053H

    N8053H

    N8053H

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    Oh no she runs great. Mine lasted maybe 50 hrs. To me that is not long enough. I went with stock tubes and like them. Also those short pipes are hard on exhaust valves. You want your exhaust valves to last longer using them, plug them when you shut down to stop the cold air from reaching these valves while they are hot. My CHT's were both even. You can not get better then this.

    I love this sound..

    [video=youtube;XZh3JLMg9Bs]https://www.youtube.com/watch?v=XZh3JLMg9Bs[/video]
     
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  2. Dec 12, 2018 #42

    N8053H

    N8053H

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    Scott told me all the cranks that have failed were operated at or above 25mp. in cruise flight. They all happened while at this power setting. That tells me a lot. Using dual carbs if one gets out of sync at those power setting, you could get preignition. If this happens in one cylinder, something must give. Rotax see's this a lot in their two strokes that use dual carbs. Ask anyone who knows Rotax cranks or works on them. 90% of the cranks will be out of phase. They are pressed together. Something must give, the crank slips. If it was a solid crank it would break. The 582 might have a solid crank for those are known to break.
     
  3. Dec 12, 2018 #43

    Pops

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    They sound great, I would pull the airplane out of the hanger and start it up just to hear the music.
     
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  4. Dec 12, 2018 #44

    Rockiedog2

    Rockiedog2

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    from Tony

    >>>Those exhaust pipes look to be drain pipes. I tried this myself. They will crack at the bend in about 6 hours of flight. Maybe a little less.

    >>>Oh no she runs great. Mine lasted maybe 50 hrs. To me that is not long enough.

    so it was 6 hours, now it's 50. :ponder:
     
  5. Dec 12, 2018 #45

    TFF

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    Having balanced temperatures are always the goal. All temps as close to ideal. It means all is working well and efficiently. My example. You have two cylinders with matched CHTs but one of the EGTs is way low. So you have to think out what is the problem really. One cylinder is ideal so it is operating max efficiency. The other needs a fix of some sort. What is going to be up to whatever the real problem is, baffling, mixture distribution, timing, mechanical, something. So the goal is to get the EGT up on the low cylinder, but you are already running at the CHT you want. You don't want to just lean that cylinder and have the CHT skyrocket. The combinations on how to fix it is specific to that one installation. All Im really trying to get across is low might not be the good cylinder. You don't want to mess with the one that is working right. You want to bring up the straggler, not neuter the good one. .
     
  6. Dec 12, 2018 #46

    Rockiedog2

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    ok understand that. that's what I've always done. Thanks
     
  7. Dec 12, 2018 #47

    N8053H

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    Looking back it sure seemed like 6 hrs. After looking in my logs it was closer to 50 or 50 some hrs. I replaced these twice one summer. That was enough for me and they came off. I put 140 hrs on this airplane that summer.
     
  8. Dec 12, 2018 #48

    N8053H

    N8053H

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    Also I mention the crack was at the bend and not the flange. What I believe was happening, at that bend the pipe would get so hot it turned blue. When cruising 80-90 mph there was so much force on that pipe it would start to crack at that hot point in the bend. I did not always fly this fast why I believe I saw the difference in time between the two breaks. Heck I may have even missed this the first time for a few hours. In other words I was flying with cracked pipes. Once I noticed this I paid closer attention to these pipes.

    I should also mention this was happening before I upgraded this engine. I went through this right after purchasing this airplane. I found she was so nose heavy I needed to remove all the weight I could from the nose of this airplane. This airplane was a few inches forward of the most forward CG limit. I removed almost thirty pounds from the airplane nose/ cockpit and still had to add 17lbs ballast to the tail. She flew great after I did this. Before she was very heavy on the stick. I mean heavy. I could have trimmed her but she went on the scales and I fixed her. But this is another story for a different thread.
     
  9. Dec 12, 2018 #49

    Rockiedog2

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    Yeah Tony I know all about that; I can't remember anything anymore.
     
  10. Dec 13, 2018 #50

    Pops

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    I wake up in a new world everyday. It's GREAT !
     
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  11. Dec 13, 2018 #51

    N8053H

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    Yes my wife claims I suffer from CRS. Can't Remember Sh## syndrome. I told her this is why I use a check list even when flying my little simple airplane.
     
  12. Dec 19, 2018 #52

    Dee

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    Fuel tank is vented. Carb psi is 3 pounds with electric pump and 0 PSI with mechanical pump. I found that the mechanical pump is broken and will replace it. Hopefully this will resolve my problem. Thanks for your help.
     

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