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Thread: 1980 sport mikuni carb idles good at first... carb interchange

  1. #1

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    Exclamation 1980 sport mikuni carb idles good at first... carb interchange

    first off what carb cane stock on a 1980 d50 2.6 spring edition sport California? And can you swap it with a 32-35 mikuni? I also have a carb off of a 1982 from a truck I I just stole at auction for 50 bucks!
    Now for my problem is that I had the carb rebuilt and put it back on and it was running rough. I cleaned and rebuilt distributor put a new coil oem cleaned the emissions galleries put a new cat and muffler and put ngk bpr5 plugs in it with a 190 thermostat, jiggle valve at 12 oíclock when your standing in front of the motor. I flushed the cooling system also. I took off the valve cover and put the mark on the cam gear at 12 oíclock and inserted the distributor marks aligned and it twisted in rotor pointing at #1 on cap. Timed at 7 degrees. I replaced the fuel filter and vac lines also. It would start and idle well and then it wants to crap out when it gets warm.
    After about 3 weeks of researching and spending all my time after work and on weekends on it my girlfriend has had enough of her lack of attention ahaha
    Ire-removed the carb and there is a couple of things I noticed, the intake has a pretty big puddle of gas in it. Also the holes in the gasket look to be partially covering some of the galleries and I think one of the check ball things is missing on the drivers side of the carb.
    Also when I look down the carb while itís running it is making a loud gurgling crackle noice and it looks like fuel is spraying into the primary under the choke. And when the car is off and I twist the throttle linkage the squirt in the primary isnít a solid stream itís more like a small spurt.
    I hope my description can stir up some troubleshooting ideas so my ol lady doesnít leave me aha donít worry Iíll never get rid of the truck lol Iíll be donating after I post this because this place is the Bible for these trucks and it is badass how much work is put into it. thank you in advance for any knowledge

  2. #2

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    The small stream of fuel is from the accelerator enrichment pump. That shot of fuel is letting you know it's working so that is good. You won't get any fuel from the primary or secondary jets while the engine is off - it's all engine vacuum doing the work. I know how sensitive these carbs are and as a result I'm always 'fanatical' about trimming the internal gaskets of overhang. I pin and align all of the vacuum galleries and open up any restrictions with a small drill bit by hand and use a sharp knife to trim off any gasket material overhanging in the throats. Kits are hit and miss when it comes to the quality of the gaskets. Do all of the basic checks - check the fuel level in the bowl and make sure the float is set correctly. Also check the auto choke function. If it's not opening when it's warmed up it'll drown in fuel. Are your fuel lines' orientation correct? (crossed fuel lines will starve it of fuel as soon as you open the throttle) Is your air/fuel mix needle in the ball park? IS THE BRASS FUEL CHECK VALVE & THE BALL BEARING IN THE CARB BODY? If you've lost them, it won't be running. They are hell easy to lose if you've never messed with these carbs.
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  3. #3

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    Quote Originally Posted by geezer101 View Post
    The small stream of fuel is from the accelerator enrichment pump. That shot of fuel is letting you know it's working so that is good. You won't get any fuel from the primary or secondary jets while the engine is off - it's all engine vacuum doing the work. I know how sensitive these carbs are and as a result I'm always 'fanatical' about trimming the internal gaskets of overhang. I pin and align all of the vacuum galleries and open up any restrictions with a small drill bit by hand and use a sharp knife to trim off any gasket material overhanging in the throats. Kits are hit and miss when it comes to the quality of the gaskets. Do all of the basic checks - check the fuel level in the bowl and make sure the float is set correctly. Also check the auto choke function. If it's not opening when it's warmed up it'll drown in fuel. Are your fuel lines' orientation correct? (crossed fuel lines will starve it of fuel as soon as you open the throttle) Is your air/fuel mix needle in the ball park? IS THE BRASS FUEL CHECK VALVE & THE BALL BEARING IN THE CARB BODY? If you've lost them, it won't be running. They are hell easy to lose if you've never messed with these carbs.

    Okay so can I use a carb off of an 82 2.6? They look different in a few ways.
    also I have the ball and check valve but there is a galley next to it that is tapered at the bottom, does another check ball go in there? Also there was no hole in the gasket for it so I think that might be why the fuel was spraying into the primary throat.

  4. #4

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    The Mikuni only has the one brass float and ball bearing. The brass check valve only fits in one gallery so you're safe. It's unlikely they didn't punch the holes for all of the fuel + vacuum circuits. All of the 2.6 carbs swap over but make sure they have the necessary sockets for electric solenoids as later model trucks have electronic feedback carbs and they won't work without a signal from the control module. You can 'solid state' them to work but I'd have to go into a detailed post of converting it and it requires a number of mods that are a little complicated. If in doubt - post up pics. They will more often than not lend clues to what/if there are underlying issues that are causing problems.
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  5. #5

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    Right on I will post pics tonight and the other 2 carbs I have have the black plastic body but still only 2 Black and white wires like my original. Also have the three vacuum ports instead of the one at the base of the carb and the two spread out vacuum ports with the rubber fitting on the side that go to the solenoid on the fender instead of the single one by the coil that my 1980 has

  6. #6

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    use a little rubber cap. doesnt need vacuum LINES in most places, just a cap

  7. #7

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    Quote Originally Posted by Salteen View Post
    use a little rubber cap. doesnt need vacuum LINES in most places, just a cap
    I live in California lol

  8. #8

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    you have to have all vacuum lines on??? thats ridiculous. i live in south carolina, no inspection, no emission laws.

  9. #9

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    Everything must be factory setup and fully functioning it’s thorough aha

  10. #10

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    You'll need a Cali emissions carb. Gotta love 'em
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  11. #11

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    welcome to the land of feds who get butthurt over a little tricked out mini truck, but will gladly allow oil mines to be planted on the coast if it means more dollars to them. crooked

  12. #12

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    So I was cutting the holes out of the carb top gasket that were missing and it has some channels cast ito the carb. Do I cut those out too? And also the meeting surface looks a tiiiny bit warped. Can I correct this with a softer gasket the same thickness?

  13. #13

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    Ignore channels in the base of the carb. The ones that will grief you are galleries between the body and the throttle plate (misaligned gallery holes in the gasket - use a drill bit the same size as the gallery and twist them out by hand) and overhanging gasket in the throats between the top cover and the carb body (use a new sharp blade and gently plane it away). Make sure there aren't loose cardboard fibres hanging off any trimming you've performed. It's a few extra minutes of work and it's fiddly, but it means you'll get the most out of your fresh carb rebuild. And another tip - once you know you've got the gaskets trimmed as good as you'll get it, make sure you've got them aligned and assemble it, then give the top cover a couple of light hits with a soft faced hammer to seat the gaskets in, then check your screws and retighten as required. Don't attempt to reface the top cover, the gasket should be enough to make up for any minor alterations to clearances.
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  14. #14

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    Okay I cut the channels out before reading this because I have another gasket just in case, can I run the one I cut still?

  15. #15

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    Yeah it shouldn't affect anything Are you still using the original bakerlite spacer? Make sure it isn't cracked anywhere or it'll have an air leak in the worst place...
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