carburator tuning

[dave]

hello guys,
  i have a b-new ma-3a carb for my 0-235 lyco,  can anyone help me on how to get this "tuned"....what would be the EGT range from FULL RICH TO FULL LEAN @ full static?....how do i know the mixture is ADJUSTED right?..appreciate your help...

[Juan Rivera]

The only adjustment is for Idle mixture, at idle the mixture is correct when the RPM increases slightly when you move the mixture to Idle cut off just before the engine stops.

[Dan Patch]

The only adjustment is for Idle mixture, at idle the mixture is correct when the RPM increases slightly when you move the mixture to Idle cut off just before the engine stops...

Juan is right.  Set the idle mixture for smooth operation and a slight rise on idle cutoff.  

The physical size of the main jet sets the full rich performance of the carb above idle, and you are in charge of the lean performance.  Presumably, your carb is properly jetted for your particular engine.  It is possible to have the wrong main jet installed, I suppose, but I don't have any direct experience with this happening.  Absolute EGT readings aren't terribly useful as the probe location(s) and other factors play a role in what they read, but in general running full rich at sea level you should be about 150 F or more below your peak EGT leaned out.  (Be careful checking this out as you don't want to be running lean at WOT at sea level!)  Having a fuel flow gage to verify that the engine is getting close to the book value of fuel consumption at full rich provides a nice sanity check.  

Bottom line is that you need to see the EGTs go up significantly when you lean to verify that your main jet is big enough, and you shouldn't be blowing black smoke and running rough, full rich, or the jet is too big.  Either condition (wrong jet = too rich or too lean) is unlikely.  Other than that, there isn't any tuning involved, other than what you do normally by proper in-flight, mixture management - which is a whole separate topic.

[Matt]

Absolutely agree with what DeltaPop posted.  A couple of
additional comments.  Each model of MS carb was used on
lots of different engine/airframe setups, each of which may
have gotten a different jetting/venturi.  

Since this is an experimental application,  that adds some
unknowns.  Airbox/filter design, pistons, compression ratio,
and exhaust system design may have significant effects on
jetting.  What DeltaPop posted about checking the setup is
correct.  Just keep in mind that the carb  you have, though
correct by the application book, may require some changes
to work properly.

There are writeups in the yahoo archive about people drilling
out main jets to enrich the mixture.  Sounds kind of tricky,
because there is no going back.

Matt-

[dave]

thanx to all ...always very helpful...!!!
  i have the carb hoooked up to a c-150 style airfilter/ carb heat box...stock filter, stock engine.0-235 c1b..