Carburetor trouble – HELP PLEASE!
Thread Starter
Race Director
Joined: Sep 2001
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From: Southern Indiana
Carburetor trouble – HELP PLEASE!
I just took the carburetor out of my truck, cleaned it (by soaking the metal parts in carb cleaner) and changed the seals. I also checked the Dry Float Level, Float Drop, Vacuum Break, Secondary Throttle, Fast Idle, and Unloader Adjustments. I slightly changed the Dry Float Level and Fast Idle Adjustments to put them within specs. The others were already w/in spec. However, when I put it back on the truck, I now have a major new problem that I didn’t have before. The engine idles fine now, but stumbles and dies any time I bring the RPM past about 2500. I’m not sure what I could’ve done that caused this. Please Help me!
The truck is a 1982 Datsun 720 Pickup. The carburetor is a Hitachi Model DCR 342. Here is a blowup of the carburetor, showing all parts and part labels. http://www.geocities.com/rworkman98@...l.net/carb.htm I put this in the C3 tech section, because I figure you’re the only people who know carburetors. I couldn’t find a forum anywhere devoted to this truck.
The truck is a 1982 Datsun 720 Pickup. The carburetor is a Hitachi Model DCR 342. Here is a blowup of the carburetor, showing all parts and part labels. http://www.geocities.com/rworkman98@...l.net/carb.htm I put this in the C3 tech section, because I figure you’re the only people who know carburetors. I couldn’t find a forum anywhere devoted to this truck.
Last edited by xwing; Jun 13, 2007 at 03:41 PM.
Limping across the line
Joined: Oct 2002
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From: Peoria Az
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
We don't know a darned thing about Japanese carbs, but here are some general comments on your issue:
Below 2500 rpm, the carb is generally operating on the idle circuit and the transition circuit - all fuel is flowing from the idle mixture hole and through the transition slot. Once you get above this range, the main discharge circuit starts feeding the fuel. If you have a lean-out and fuel starvation issue at elevated rpm, you have a main circuit fuel feed problem. This can be caused by an obstruction in the main discharge circuit or any issue causing a blockage or a discontinuity of the circuit (such as an incorrect gasket). You might want to take the carb back apart and trace through the circuit using WD40 and the litle red plastic tube that comes with the can: By blowing WD through the circuit, you can trace it out and verify that you're flowing fuel all the way from the primary jets to the discharge nozzle. Hopefully this will identify where you're seeing a problem.
Good luck...
Below 2500 rpm, the carb is generally operating on the idle circuit and the transition circuit - all fuel is flowing from the idle mixture hole and through the transition slot. Once you get above this range, the main discharge circuit starts feeding the fuel. If you have a lean-out and fuel starvation issue at elevated rpm, you have a main circuit fuel feed problem. This can be caused by an obstruction in the main discharge circuit or any issue causing a blockage or a discontinuity of the circuit (such as an incorrect gasket). You might want to take the carb back apart and trace through the circuit using WD40 and the litle red plastic tube that comes with the can: By blowing WD through the circuit, you can trace it out and verify that you're flowing fuel all the way from the primary jets to the discharge nozzle. Hopefully this will identify where you're seeing a problem.
Good luck...
Thread Starter
Race Director
Joined: Sep 2001
Posts: 16,507
Likes: 84
From: Southern Indiana
Oh and try a better search engineDatsun Forum
Melting Slicks
Joined: Mar 2004
Posts: 3,472
Likes: 18
From: Lake Ozark, MO
If you still have the old gaskets compare them against the new..you may have blocked a critical passage. On Japanese carbs there are many variaitions (especially the Cali C.A.R.B. cars/trucks) of carbs. You may have gotten the wrong kit....
