I recently changed the needle in my Doug Eichner carb on my 440ex for a richer setting. It was runnig too lean. My problem now is when I go to higher altitudes, the low to mid range wants to spit and sputter. Topend feels great. At home it runs like a top in all rpm ranges. Which way do I need to go on needle height? Lower it or raise it?

 

Anyone???

 

Here's a good ratio to go by:
For every 30 degree change - change one jet size. Example 175 to 180 Cooler is richer
For every 3000 feet of elevation - change one jet size Higher is leaner
For every 30% change in humidity - change one jet size Drier is richer


With elevation the atmospheric pressure is lower. Thus the need to control pressure thru the carb. You could advance your timing to compensate, but that is not easy. So by running lower octane you can burn the fuel faster and increase internal vacuum signal.