Carburetor trouble

[rworkman98]

I just took the carburetor out of my truck, cleaned it and changed the seals. I also checked the Dry Float Level, Float Drop, Vacuum Break, Secondary Throttle, Fistle 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@sbcglobal.net/carb.htm

[]2eDeYe]

The link doesn't work.

 

Accelerator pump?

[banzai510(hainz)]

I hate Stock carbs to many varibles to go wrong when putting them back together.

 

sticky float needle valve causing carb to go dry.

But Im just winging this here. if 2500 is OK I assume the main jet is clear

[rworkman98]

2eDeYe;9773']The link doesn't work.

Accelerator pump?

I fixed the link. Thanks! I don't see "accelerator pump on the parts diagram. Where would it be?

 

I hate Stock carbs to many varibles to go wrong when putting them back together.

 

sticky float needle valve causing carb to go dry.

But Im just winging this here. if 2500 is OK I assume the main jet is clear

It seems to have trouble getting gas anywhere above idle, but starts having the real problem starts ~ 2500 RPM.

[datzenmike]

First did you remove the primary and secondary main jets? They are below the fuel bowl behind 12mm plugs and could have been interchanged causing an extreme rich condition. The primary jet, furthest from the valve cover, has a smaller hole than the secondary. Were any other jets, air bleeds or emulsion tubes removed and possibly put back in the wrong places?

 

It is possible that the carb is running dry at speed. On the carb front is a small window to view the fuel level. Find a deserted section of road and drive untill the motor begins to stumble. Immediately turn the engine off and pull over and check that there is indeed fuel showing in the round window. If the carb is running dry you don't want the fuel pump to refill it as you stop, so turn the key all the way off. As always use all possible caution and common sense when doing this on the roads.

[rworkman98]

First did you remove the primary and secondary main jets? They are below the fuel bowl behind 12mm plugs and could have been interchanged causing an extreme rich condition. The primary jet, furthest from the valve cover, has a smaller hole than the secondary. Were any other jets, air bleeds or emulsion tubes removed and possibly put back in the wrong places?

 

It is possible that the carb is running dry at speed. On the carb front is a small window to view the fuel level. Find a deserted section of road and drive untill the motor begins to stumble. Immediately turn the engine off and pull over and check that there is indeed fuel showing in the round window. If the carb is running dry you don't want the fuel pump to refill it as you stop, so turn the key all the way off. As always use all possible caution and common sense when doing this on the roads.

 

Thanks for the tips. I did make sure not to interchange my primary and secondary jets. I also checked the fuel level. I can't drive it on any roads, since it can barely make it out my driveway. But I did have my wife hit the accelerator w/ the truck in neutral, and I watched the fuel in the window. It is slightly below the indicator dot, but only by about a mm or two.

[Duke]

vacuum leak?

[ggzilla]

Most common problem: The gasket was put on incorrectly, often upside down. I've seen it a million times, and done it myself more than once.

 

I would take the top back off and ensure the gasket lines up with all the passages. Some rebuild kits have more than one gasket, so make sure the right one was put on.