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1980 carburetor tuning

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Hey All,


wondering if you guys have schematics or a video of how to tune the 1980 carb. I got a manual but it is not telling me whats what. I get a lot of blowback out the muffler when I give it a bunch of gas and let go of the throttle. Trying to tune it to stop it as I know that means I am running to rich. 

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Don't mess with the carburetor. Have you checked the valve lash yet? 


Blowback.... I assume this is loud popping and backfire on deceleration?


There is a device called the 'anti-backfire valve'. Maybe the signal vacuum hose is off making it inoperative. It senses an overly high intake vacuum on high speed deceleration and opens a valve letting air into the intake to lower it. Of course it it is a tightly closed system that  regulates the intake manifold vacuum.


Looking for '70 Anti-Backfire Valve Detail - Engine & Drivetrain - The  Classic Zcar Club

The upper hose is filtered air from inside the air filter. Pull the hose off and put thumb over end. Rev engine to 3,000 and suddenly release. You should feel a suction if the AB valve is working. The smaller hose is the sense vacuum line and connects to the intake. The larger bottom hose directs filtered air to the intake when the AB valve is working. The sense hose may be off or cracked.


Try this first and let me know. There are other things to try.



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