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MZ202 carb jet settings
#1
I have a EXL with a MZ202 45 hrs on it. And new pistons. Bought it in FL where of course it is sea level. I am in New Mexico where the field elevation is 4100 ft. Can anyone tell me where to set the Needle jet clips on the Carbs? The temps are running low. It is set for sea level altitude now. Suggestions? Thanks Vic
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#2
Vic,

Generally you will have to lower the needle a little for higher elevations to reduce the fuel uptake in the thinner air to keep the ratio correct. Temps are running low because you have too rich of a mixture now with sea level jetting. Unfortunately there is no set formula for jets for a given altitude and temperature as different engines vary somewhat.

Reducing the main jet affects the mid to full power range. You can reduce the main jets based on your altitude and ambient temperature based on a chart such as this which is derived from variations in air density with altitude and density. Refer to the third chart down: http://www.ultralightnews.ca/bing/bingjetchart.html.

Changing the needle affects mostly midrange. Once setting the correct main jets from above I usually pick up in a hover and watch the nose to see if it jumps occasionally due to the engine being too rich. I adjust the needle until raising it one more notch will make the nose jump but it stays smooth where I am at. Then you are as close to being too rich as you can get which is a good place to be. Watch your EGT's to make sure they don't get too high (should stay below 1150) and check the plug color after you hover for one minute at what you feel is the correct settings to be sure they are the tan color you are looking for.
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#3
I have a main jet 195, flying at sea level there are no problems. but I made a flight at high altitude with the same cast and the maximum altitude reached was 3300 feet. the EGT had dropped brusquely to 800 degrees F. and I had no more power available. I like john says that we must reduce the main jet to have a leaner mixture.
I'd like to have some feedback.
Maurizio
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#4
Thanks I have  leaner jets coming in with instructions from the factory how to dial it all in. Yall have been a great help. I will keep you updated.
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