I would be very grateful to get an answer a fundemental question around sizing SHA 12.14 Main jet sizing in context of Relative Air Density (RAD).
I know and appreciate the methods for sizing the main (and only) jet using the RPM, Engine temperature and spark plug condition as well as using Gunson Colortune. However, I would like to augment these methods using Relative Air Density that effectively takes into account all the weather factors- as a starting point for a testing weekend/ session.
The Question
If I have an engine with an SHA 12.14 Carb performing perfectly with a 58 size main jet at 100% RAD, what main jet should I try if, say, RAD increases to 105%?
Should I, as a rule of thumb, estimate the next jet size by increasing the '58' by 5%- i.e. 58 x1.05= 61 (rounded up) jet size? Or is there another metric based approach?
Using RAD does provide a means to account for temperature, altitude, barometric pressure and humidity- since RAD is a product of all of these factors. So my question is not engine specific but very much a generic one.
I am not looking for a definitive engine tuning metric as that would of course be engine dependent but I am looking for a generic/ general rule of thumb guide.
Any help will be much appreciated.
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Dellorto SHA Carb Jet Sizing by 'Specialist' << You are here!
