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Carb Tuning Techniques

Discussion in 'Mitsubishi Minicab' started by Don-in-Japan, Dec 13, 2008.

  1. Don-in-Japan

    Don-in-Japan Member

    These sheets are from a Mitsubishi Minicab (Year and model I've forgotten now), but the carb setups and design are similiar to most Japanese models, although in slightly different positions. The diaphrams, linkages, and tuning techniques should be pretty close to many, and at least it is a starting point.

    Like I've said, carbs are the Achilles heel in these vehicles. The sheets will do little for a carb that needs an overhaul, or a complete swap.



    Last edited by a moderator: Dec 14, 2008
    Trey 4x4 likes this.
  2. TetsuKuma

    TetsuKuma Member

    Hi Don,
    Thanks for the even more detailed carb (with translation wording) diagrams. The hardest part of doing any of these adjustments are some of the contorted positions required of hands, arms and body! Front right side engine bay vs. rear bed hatch access.
  3. Dan

    Dan Member

    Those pages look really familiar...I have the american manual for a slightly different carbureted mitsubishi. (89-95 mightymits truck 550cc) I put that chapter of the manual online at this link

  4. Don-in-Japan

    Don-in-Japan Member

    I appreciate all the thanks I continue to receive for these translations. :)
  5. zardoz

    zardoz Member

    Keep up the great work Don.... without your translations.. these pages would be useless clutter! :) Sure glad you are here to help us keep our little monsters alive! :D

  6. 3banger

    3banger Member

    Has anyone ever had problems with the "variable venturi" system inside the carb? I'd like to figure out a way to test mine.
  7. sdjenk

    sdjenk New Member

    carb for 3G81 engine problems

    Hi I recently bought a Mitsubishi U15D truck and it has carb problems. I have had it apart several times and it seems to be dumping to much fuel and won't idle at low RPM'S I don't know much about this style mikuni carb I have worked on a lot of motorcycle carbs but not like this. Does anyone know about working on or know were I can get a nother carb? Thanks, Steve
    Dirtdiver and Crespo like this.
  8. akguy09

    akguy09 Member


    depends on which truck and what year, my 88 U15T they are on the left side of the motor. Easily accessible from under the truck
  9. heywire77

    heywire77 New Member

    hey if you still need help with the carb let me know i can rebuild it for you.:)
    Antione Graham likes this.
  10. muddy moose

    muddy moose Member

    Very cool. Tjamx for taking the time to.share this information. Even though you knew the repercussions of your kindness would result in thousands of questions.hahaha
  11. c64us

    c64us New Member

    I had trouble when I first purchased my little truck, would idle fine and ran well up until half throttle, beyond half throttle it would cut off. The carb has a low speed fuel supply path and a high speed fuel supply path, the high speed fuel supply path was clogged completely closed, cleaned it out and it fixed that problem. It also needed a new needle that attaches to the float, I made one from a Holley Carb needle, I just had to machine a little off the outside diameter.
  12. EddieJoe

    EddieJoe New Member

    Tuning techniques are very special and i am lazy at learning this technique and most of the times i get it fixed by specialist. But soon i will get command over it.
    Last edited: Apr 23, 2015
  13. serge

    serge Member

    anyone have a written copy oh how to tuned the carb? im having issues in this department and any info would be great.
  14. Don-in-Japan

    Don-in-Japan Member

    Hey guys.. sorry I haven't been on this forum in a while. It seems my pics are gone.. likely a migration or update issue.

    But here they are again.. luckily I had emailed them to a couple people, and they were still floating around in email land.

    If you cannot zoom in, right click the mouse and click on the "View image option". Should be able to click to enlarge.

    Attached Files:

    Last edited: Nov 26, 2015
    wbmitch likes this.
  15. DonBadajoz

    DonBadajoz New Member

    Thanks Don for re-posting the images... This will help out alot.
  16. Inane2

    Inane2 Member

    Thanks Don, glad to see your name pop back up in the forum. I've been out quite a while as well.
    Don-in-Japan likes this.
  17. Sodbuster

    Sodbuster New Member

    I'm thinking of trying a 36 mm PWM Keihin carb of a 06 650 Artic Cat. This carb has a electric wax choke, main jet 155, 48 slow jet with a rubber manifold between the head and carb with a manifold vacume port to run accessories. I don't no if the bolt pattern will except this carb however ? I want to ditch all the choking emissions that is restricting fuel/air and be able to jet. When and if this can be done next step will be a 10 HP shot of NOS. I have worked with NOS in the past and it's the fastest and safest way to get you into your power band, very safe cost effective.
  18. Sodbuster

    Sodbuster New Member

    I pulled the carb of today and took a look around dang these things have a lot of useless vacume hoses. After I took my carb of and grabbed my 36 mm Kien carb looks like I have plenty of room. Than I grabbed the mounting flange that will attach the carb to the intake manifold. I have a problem to over come, my flange is 70mm from center to center mounting hole and the intake is 80 mm. So I jumped on line and searched closes I can come up with is 75mm from hole to hole. I may be able to long gate the holes and make do and this will happen IF I can't come up with anything, maybe somebody on here can. There is a couple problems that will need to be deleted on this swap. First is There are two water jackets that inters the back of the carb to warm the float bowl these will need to be plugged, I'm thinking taping them and screw in allan studs into place this should take care of this. Next is manifold vacume for power brakes and accessories,, this is no problem two nice size ports on the manifold + my carb has one. Next is ported vacume for vacume advance ? This is a problem my 36mm Kien has none, nor is there going to be any on the manifold just have to figure this one out when I come to it,, may not be a problem at all.

    My mini rig is a 96 Mitsu with a automatic and A/C and once I do this install I'm going to loose the TPS this may be a problem because when and if I disconnect the TPS and take it for a drive I loose a nice hard shift from 1st to 2nd it comes in kinda lazy. I'm not sure if this will be a problem I'm still looking for a speed sensor " AKA" 3 gear lock out speed governor, that has been no were to be found all I have is 1st and 2nd gear but I will find this little Ba$$tard :) I no it's there some were. Next will be the A/C Idle up switch,, not sure how to fix this just have to turn on the A/C and see how nerves it gets ? May not be a issue.

    please jump in and give me some feed back guys.. Thanks, Greg
  19. J.Bradley

    J.Bradley New Member

    Hello All,

    I just bought my first Mini Truck and need some assistance. The Carb was full of ethanol goodies so I have cleaned it and looks good now, The issue is I need just the gaskets and o-rings, I tried to save as much as I could but some never make it. Is there somewhere I could get just the gaskets? Also it there a way to find the age? I found a Disney world tag and badges but have not found a way to tell the year. It is a U14DQHPDL2M.

  20. Don-in-Japan

    Don-in-Japan Member

    Check on the seatbelt where it bolts to the body. Should have a tag sewed on stating month and year of manufacture.
  21. J.Bradley

    J.Bradley New Member

    I saw the post to look there but there are no seat belts in there. I was told it is a 1991 but cannot find where they made the U14d past 1990.
  22. Don-in-Japan

    Don-in-Japan Member

    Take a picture of the data plate. I may be able to run the numbers tomorrow.

    No promises though. Really needs the info off the original/export title.
  23. Dan

    Dan Member

    They stamped a serial number on the body under the drivers seat. These Lefty's were imported through 1994. Post the number and I'll see if it's listed in the books I held on to.
    Alan Hairston likes this.
  24. Dan

    Dan Member

    It appears that the carb did not change for the entire run of the Americanized Mitsubishi. MD 617058 is the gasket kit for the carb body. It doesn't include the pump diaphragm MD 617046.
  25. J.Bradley

    J.Bradley New Member

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  26. Dan

    Dan Member

    The info on the plate is just for the assembly options at the factory. The serial number of the truck is stamped directly on the white portion of the body to the rear of the seat opening.
  27. J.Bradley

    J.Bradley New Member

  28. Dan

    Dan Member

    Your truck was built in the second term of September in 1991
  29. J.Bradley

    J.Bradley New Member

    Great, Thanks for the help. On the hunt for carb gaskets or a rebuild kit now.
  30. Crespo

    Crespo New Member

    I need mine rebuild how will it cost me for the 3G81 carb kit

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