Over Jetting

by Barb & Eric

"So I went to my local FLAP and found the biggest jet he had, a 130. Gee. I didn't think I was supposed to feel acceleration or be able to break 60mph on the highway. All that and significantly cooler oil temps at speed."

We think you might have gone with the wrong solution. The stock main jet for your bus was a 116. You are probably running too rich in the lower RPMs while accelerating, which will wash out your rings with too much fuel in the lower RPMs. Instead, you probably would be better off with a smaller air correction jet in your carberator.

There is not one jet, but three jets that you have to have right to match the engine size, air cleaner, and even how the different engine compartments breath. The pilot jet sets your idle with the air/fuel adjusting screw doing a little fine tuning. The main jet does the low to medium RPM acceleration fuel delivery. The air correction jet actually allows more air into the fuel system the bigger this jet is and it controls the fuel mixture at the higher (about 2,500-4,000) RPMs. So check out your Bentley manuals for your size engine and then check the other Bentleys for your bus and see if you need to compromise between the two.

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