Please note, the following information is provided as a supplement to the normal, simple installation process. Green Sky Adventures, Inc. ships HAC kits calibrated, and ready to install. Simply change the appropriate main jet, and that's it. However, if there is ever a reason to doubt the function of the HAC, or if one wishes to perform a periodic inspection, The information below is "must have"

Early HAC chambers were shipped with instruction to verify calibration upon initial installation and annually. Within a few years, field experience indicated calibration from "factory" settings does not change (unless a failure occurs). The previously removable screw 2, above, in current production, is sealed over. Calibration can still be checked, but adjustment  cannot be made without removing the sealing material and screw.  Variation from proper calibration  can alternatively be corrected by custom jetting change. For that reason you may see conflicting recommendations for jetting.

Calibration check requires:  Density Altitude information and  the corresponding HAC metering pin position information. (see table, below)  Because the metering pin moves with changes in Density Altitude, it's position is referenced to that and can be measured. Metering pin position measurement is taken by measuring the space between the top of the metering pin and the end of the vacuum connection pipe.  (Dimension E) Example at right:  After determining Density Altitude and the corresponding Dimension E, a wooden insert was cut to that length and dropped into the vacuum connection pipe. It should be flush with the top. Allowable variance is plus or minus .5 mm.  If the metering pin is out too far,  (dimension E too small) the sealed screw must be loosened to bleed pressure from the sealed side of the chamber.

If the metering pin isn't out far enough (dimension E too large), loosen sealing screw, and apply slight suction to the vacuum connection pipe with the remaining tubes blocked off. Close the sealing screw. At this point, the metering pin should be almost to the top (Dimension E = 0) then, just as above,  loosen the (previously) sealed screw, gradually,  bleeding out pressure till the pin goes back down and dimension E is correct.

http://weather.noaa.gov/weather/ccus.html http://wahiduddin.net/calc/calc_da.htm

Metering Pin Indexing Table Dimension E (mm) / Density Altitude (ft)  12.0 mm  Max Diaphragm deflection 6.0 mm 8,940 12.0 mm -5,331 5.5 mm 9,842 11.5 mm -3,937 5.0 mm 10,745 11.0 mm -2,625 4.5 mm 11,647 10.5 mm -1,312 4.0 mm 12,549 10.0 mm 0 sea level 3.5 mm 13,451 9.5 mm 1,312 3.0 mm 14,271 9.0 mm 2,543 2.5 mm 15,092 8.5 mm 3,773 2.0 mm 15,912 8.0 mm 4,921 1.5 mm 16,732 7.5 mm 5,987 1.0 mm 17,470  7.0 mm 7,054 .5 mm 18,208 6.5 mm 8,038 0 mm 18,865

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Density Altitude Sample We worked a sample on Mar 10, 2003 out of Gainesville Florida. Above is the view of the National Weather Service input, and the the DA calculator results. As luck would have it, on this morning, the DA calculated out to 0 feet msl.

Jetting changes are required. There are a variety of conflicting data in published charts. In setting up an engine for HAC operation, a technician must take into consideration the default is generally towards rich, meaning the HAC is continuously leaning the mixture. Initial jet selection therefore is larger. Below, is a recommendation which may be used as a starting point. This may not ultimately be the final combination of jets for a particular installation. As always, careful monitoring of EGT is mandatory, especially during set up process.

• Jan 2003:  Randomly checking calibration, our observation indicated a larger main jet requirement than certain published suggestions. The chart below is a modified Bing chart. These are the the jets provided with HAC kits shipped between November 2002 and Mar 2003

Measuring Deflection Sea Level 4,700 ft msl Mar 2003: In the past few months, Green Sky Adventures, Inc has performed numerous actual altitude tests of HAC chamber function. Testing was performed to verify HAC function against a published calibration chart. Field reports indicated HAC function at density altitude of 0 feet msl and below was incorrect. Prior to this date, the remedy has been to increase Main Jet size significantly.  Effective Mar 2003, All HAC units supplied by Green Sky Adventures, Inc. are checked for conformity to published calibration chart 2S 89-E

Important Clarification and Jetting Note: Standard 503 Dual Carb without air intake silencer, and without HAC was changed around 1992.  Old jetting used an 8L2 Jet Needle in Position 1 and a 2.74 Needle Jet.  On that vintage, when HAC was added, the only jet change was the main jet. It went from 158 to 185.  In the early nineties, the standard mid range jetting was changed to the current 11K2 Needle in position 2 and a 2.70 Needle Jet. This setup yielded about the same mixture, but would allow for Needle Clip adjustments, as required. (notice the early version had the clip at extreme top position leaving no available adjustment) When the jetting change was made, that change was never reflected in the  503 DC HAC jetting chart. Consequently, those who changed to the HAC setup on late engines have been reverting to the older version mid range jetting for no valid reason. Initially, HAC installation should only require Main Jet changes. Close monitoring of EGTs may indicate other changes, but only on a case by case basis. If other mid range jetting is effectively in use, initial change of the Main Jet, only, is the general recommendation.

 

3.  Slide or Piston   4.  Jet Needle Clip   5.  Jet Needle O-ring   6.  Spring Cup   7.  Slide Spring   8.  Carb Top O-ring   9.  Carb Top 10.  Carb Top Screws 11.  M6 Jam Nut 12.  Cable Housing Adjuster 13.  Cable Grommet

14.  Mixing Tube 15.  Sieve Sleeve 16.  Float Needle 17.  Float Needle Clip 18.  Floats 20.  Float Hinge 21.  Float Chamber Gasket 38.  Idler Jet 39.  Needle Jet 40.  Main Jet       Float Bracket