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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.

    Don
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    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.
    Later!
     
  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

    http://www.box.net/shared/0kpymfg7bs
     
  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

    z
     
  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
     
    Crespo likes this.
  8. candyk123

    candyk123 Guest

    Thanks for this Don!
    Now I have another question for you or anyone on this forum;

    Where are the spark plugs, and what spark plugs do I buy at the store, and do I need a special tool to change them?

    How do I check them, how will I know they are in need of changing?

    Thanks,

    Candyk
     
  9. akguy09

    akguy09 Member

    sparkplugs

    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
     
  10. candyk123

    candyk123 Guest

    Bravo Mini Van Spark Plug Location

    Oh lovely. I'm looking forward to getting under my van. Yoy. Mine is a 3g83, U42V. 3 cyl, DOHC. Does that help you or anyone else to know whether the plugs are easiest reached under the seat or under this van?

    I couldn't get it started in the end of winter, but changed the air filter and finally got it started with some persistence after that, let it run for a half hour, and haven't started it for about two weeks. Haven't really needed it, but want to make sure I'm not going to be stranded the next time I take it out.

    Any help from anyone would be greatly appreciated!

    --Candy
     
  11. heywire77

    heywire77 New Member

    hey if you still need help with the carb let me know i can rebuild it for you.:)
     
  12. 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
     
  13. 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.
     
  14. 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
  15. 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.
     
  16. 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
  17. DonBadajoz

    DonBadajoz New Member

    Thanks Don for re-posting the images... This will help out alot.
     
  18. 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.
  19. 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.
    Greg
     
  20. 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
     

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