[NSRCA-discussion] ZDZ mixture change when I fly on the back

[Rex LESHER]

Patrick

>From your descrition,  I at first thought that you might be having a fuel clunk problem in the tank, simply from having problems while inverted.
But, you also state that it does the same thing during harriers, which puts all the fuel around the clunk.   I suspicion that your idle mixture is
slightly lean.  That's what I would try first...   Just open the mixture screw 1/8 turn or a bit more.   If that doesn't work, check the clunk "line" 
in the fuel tank, it may have a perforation in it.  Also, check the gasket between the carb and the manifold for air leaks.
If all of these fail, pull out the low speed air screw and blow air from an air compressor through it.  Don't use more than about 30 lbs. of pressure
Sometimes, there's a little junk in the jet passages that causes a few problems, usually a result of not using an air cleaner, or the air cleaner gets
junk through it.  Reguardless of everything mentioned, your problem is "too lean" in the low speed department.

You didn't say wether or not this is a new engine... Even if it is new, don't discount having junk in the carb.   I've been making a living with 
chainsaws for over 20 years, and I'm here to tell you...   You wouldn't believe what you'll find in a new motor or carb...  A lot of times, drillings
never get blown out of the passages during assembly.  Most all gas engines any more are very stable, well running motors once set up
correctly.  
I hope this helps,  let us know what you find...

Rex
  ----- Original Message ----- 
  From: PPandelaers<mailto:ppandelaers at pandora.be> 
  To: mini-iac at yahoogroups.com<mailto:mini-iac at yahoogroups.com> ; gsal at yahoogroups.com<mailto:gsal at yahoogroups.com> ; nsrca-discussion at lists.nsrca.org<mailto:nsrca-discussion at lists.nsrca.org> 
  Sent: Sunday, February 25, 2007 7:07 AM
  Subject: [NSRCA-discussion] ZDZ mixture change when I fly on the back


  Hi all,



  Have a mixture issue which I suspect more of you may have experienced, maybe someone knows a cure. 



  Running a ZDZ 80 RV in a Yak 54. Prop is a Mejzlik 26x10. MTW-cannister.  Turns about 6200 RPM.



  Engine picks up wonderfully, does great 3D. but, on in back-flight, the RPM sags a lot from mid- to high-range. Don't get full power at all. Flip it around, immediately full power. From Back-flight, certainly from harrier, if I push it up for a torque, the engine hesitates big time but never quits.



  All in all, I run the engine fairly rich, it seems to be very tolerant to mixture setting as long as it's on the rich side. I have tried to lean it out to fix the back-flight issue, but then it doesn't pick up as well for 3D.



  Hope someone can help.



  Happy Landings ;-))



  Patrick

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