Jetting

There is no one correct set of jets to use, however there are some good ballpark settings for each application (i.e. 12A stock, street-port, etc.). Racing Beat delivered a carburetor that was set up to provide good performance out of the box with only minor tweaking of the idle mixture screw. Of course even that setup is probably not optimum for all applications as other engine modifications and elevation play a role. However, the average person doesn’t have the time, equipment, and knowledge to find the optimum set-up. My goal with this page is to provide the set-up that Racing Beat delivered (it works for most) and also information from other people on their individual set-ups.

This section is not as complete as it could be as I don’t even have the exact settings that Racing Beat used. Also it is quite possible that Racing Beat changed their jetting settings over time. Also Racing Beat modified the carburetor as delivered by Dellorto. I am not sure what exact changes they made.

12A Engines

12A Stock (from RB)

These settings are from my carburetor. In a few cases I am not 100% sure of the jet size and I won’t tear my carburetor apart just to find out. After my last experience with the pump jet, I need a good reason to tear into it again.

Jet	Size	Notes
Main Emulsion Tube	#7772.8
Main Fuel Jet	#230
Main Air Jet	#230
Idle Holder/Emulsion Tube	#7850.4
Idle Jet	#75
Accelerator Pump Jet	#90	Not positive on this.
Needle and Seat	#300	Pretty sure as it’s the only one that RB had in their catalog.

12A Stock (from Will Claypole) New!

This page is a write-up by Will on his experience getting the Dellorto working on a stock 12A. Will did considerable tinkering with the carburetor to improve the original RB setup. Major changes include modifying the float level and the accelerator pump.

12A Street-Port (from Brad Page)

This page is a write-up by Brad on his experience getting the Dellorto to work well with his street-ported 12A. He found that the intake manifold by Racing Beat to be the reason why people (including RB) have problems getting the Dellorto to work well with a ported engine.

13B Engines

6-Port 13B Stock (from RB) New!

I received settings from Daniel Ciarcia who got them from Racing Beat. Mazdatrix and Hayes also recommended these settings. Only the accelerator pump jet and emulsion tube are different from the 12A setup.

Jet	Size	Notes
Main Emulsion Tube	#7772.8
Main Fuel Jet	#230
Main Air Jet	#230
Idle Holder/Emulsion Tube	#7850.8
Idle Jet	#75
Accelerator Pump Jet	#80
Needle and Seat	#300

6-Port Street-Port 13B

If anyone has settings for this setup please let me know (dave@gruntled.com).