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please all MZ2 Mosquito owners... Reply
#41
vortexring - 2/23/2011 10:40 PM
If when on the ground with the rotor rpm at 100% and flat pitch and the EGT's look safe , you might not have a problem with the sustained descents causing overly lean situations, it is normal for some increase in temps.

I agree that this procedure HELPS determine if the needle-jets are correct for your density altitude.
I still feel however, that if there is ANY INCREASE WHATSOEVER in EGT's as you enter a normal descent from cruise flight, then your needle-jets are too lean.

If the EGT's remain 1150-1200 as you lower the colective to descend, your needle-jets are perfectly sized for the density altitude where you are.
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#42
Guess I'm late to this one, but wow, I'm thinking from what Brian is saying, it's way safer to be too rich than too lean. So my plugs are turning a little black in one hour, so what, if black plugs are not a problem then I'm not going to try and fix it by leaning my mid-range (which is already max rich). The old ultralight-mentality codger has little experience and lots of bad luck with engines... thanks Brian for sharing your vast experience, and for caring! -larry,
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#43
Jetting can be a complex issue to deal with. I will try to write something up on jetting as it affects our helicopter operations and post shortly. I don't want to create more confusion than assistance.
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#44
(10-20-2011, 09:03 AM)mosquito Wrote: Jetting can be a complex issue to deal with.  I will try to write something up on jetting as it affects our helicopter operations and post shortly.  I don't want to create more confusion than assistance.

Hi John,

I know this is an old treat but since then did you post something up on the forum on jetting for the newbie like me to anderstand a little more about this important topic ?

Regards,
Fred
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#45
I did post something somewhere but it's probably easier to write it up again here.

Variations in fuel, oil, ambient conditions and the engine itself preclude us from providing set parameters to adjust mixture.  The instructions below are guidelines only.

Finding the correct adjustment for mixture in a two stroke can be evasive.  The primary indicator of mixture is the spark plug color but even this can be modified depending on the contents of the gas and oil being used.  Spark plug color with a good mixture level will be a dark tan color.  Black is too rich and/or too much oil.  Light grey or white are too lean and should be avoided.  Too rich means a poor running engine.  Too lean means EGT's that are too hot and will result in a melted piston and seizure.    

EGT readings are also an indicator but should only be a guidline as well.  EGT's should typically range between 1050 and 1150 deg F when in a hover

The MZ202 engine comes from the factory with 195 jets in the Bing Carburators.  This setting is for sea level at 70F ambient temperature.   You can adjust the main jet size by referring to the chart below.  Simply find your altitude and current average temperature in chart below and adjust the size based on the multiplier.  That will adjust the main jet.  

To adjust the needle I find the best method is to set the clip to the bottom groove.  This is the most rich setting and the safest from the point of view of engine seizure.  Lift it into a hover.  If it is too rich you will feel the nose of the helicopter slightly jerk sideways occasionally due to the engine missing even though you can't hear it.   Adjust the needle to the center position and try again.  If you feel it still missing then try the top groove.   The position that you feel the miss go away is the point at which you are just on the edge of being too rich at which point the engine will run well but be as far away from seizure as possible.

   Make sure the EGT's temps and spark plug color are acceptable as well.  When doing plug color tests don't idle the engine to cool it down.  Just set it down and shut it down so as not to distort the plug color from the hover.


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#46
(11-24-2017, 04:41 PM)mosquito Wrote: I did post something somewhere but it's probably easier to write it up again here.

Variations in fuel, oil, ambient conditions and the engine itself preclude us from providing set parameters to adjust mixture.  The instructions below are guidelines only.

Finding the correct adjustment for mixture in a two stroke can be evasive.  The primary indicator of mixture is the spark plug color but even this can be modified depending on the contents of the gas and oil being used.  Spark plug color with a good mixture level will be a dark tan color.  Black is too rich and/or too much oil.  Light grey or white are too lean and should be avoided.  Too rich means a poor running engine.  Too lean means EGT's that are too hot and will result in a melted piston and seizure.    

EGT readings are also an indicator but should only be a guidline as well.  EGT's should typically range between 1050 and 1150 deg F when in a hover

The MZ202 engine comes from the factory with 195 jets in the Bing Carburators.  This setting is for sea level at 70F ambient temperature.   You can adjust the main jet size by referring to the chart below.  Simply find your altitude and current average temperature in chart below and adjust the size based on the multiplier.  That will adjust the main jet.  

To adjust the needle I find the best method is to set the clip to the bottom groove.  This is the most rich setting and the safest from the point of view of engine seizure.  Lift it into a hover.  If it is too rich you will feel the nose of the helicopter slightly jerk sideways occasionally due to the engine missing even though you can't hear it.   Adjust the needle to the center position and try again.  If you feel it still missing then try the top groove.   The position that you feel the miss go away is the point at which you are just on the edge of being too rich at which point the engine will run well but be as far away from seizure as possible.

   Make sure the EGT's temps and spark plug color are acceptable as well.  When doing plug color tests don't idle the engine to cool it down.  Just set it down and shut it down so as not to distort the plug color from the hover.

This perfect John ! Thank you !!
Fred
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