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Thread: Carburetor Adjustment

  1. #1

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    Carburetor Adjustment

    1988 Mitsubishi Mighty Max 2.6 Mikuni California Carburetor Adjustment

    How do I go about adjusting the carb to perfection? Going to the carb shop is getting pricy. Need to learn to do it myself. Is there anyone kind enough to teach me?

  2. #2

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    Anyone???

  3. #3

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    I think the general consensus here is that our Original Mikuni carbs were too frustrating to tune and keep tuned.,.even whenthey were new....

  4. #4

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    Yup, frustrating for sure. I just need it tuned to pass smog, the smog report says it is using too much gas. How do I go about adjusting the fuel?

  5. #5

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    Yes, mine was too. I'm sorry I don't know and can't help you but I think I saw some posts or stickies that were talking about tuning the Mikuni..?

  6. #6

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    I really don't have the money($60) to tune the carb. The last time I had it tuned, it took the carb shop only 1minute to tune. C'mon, it can't be that hard if it only took them a minute. Someone, please share the secret.

  7. #7

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    The Cali carb is probably the worst of the 32/35DIDTA's to mess with - if there's a fault with the emissions controls or vacuum lines you're going down the rabbit hole fast. The adjusting screws are all the same but you have a mountain of vacuum hoses and control circuits to work around. Cleaning out the EGR valve and testing that it works goes a long way to fixing rough running issues.

  8. #8

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    Carb runs great, no rough idling. Just using too much gas. Need this fixed, otherwise I can't get my 2019 sticker. I need this truck for work. If you are interested in moving to California, just know you will have smog testing to deal with. Help, someone.

  9. #9

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    Does your truck have an O2 sensor and what condition is it in? This can also be a cause of high fuel usage. Here is a list of common problems that affect fuel economy (not all of them will be relative) -

    http://dannysengineportal.com/excess...l-consumption/

  10. #10

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    Do they make smaller jets for this carb or does it use metering rod? Can you braze the jet and drill a smaller hole?
    I know on my 86(years ago).. i swapped a carb from a 1978 arrow and it fixed a ton of driveabilty issues.

  11. #11

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    Guys, all I know is the carb shop uses a screwdriver and they twist the screw to a certain way to adjust the carb right. they do it in less than a minute. I just don't know the secret, they also won't let me see how they do it because obviously I'd figure out how they do it.

  12. #12

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    Quote Originally Posted by Can1991Ram View Post
    Do they make smaller jets for this carb or does it use metering rod? Can you braze the jet and drill a smaller hole?
    I know on my 86(years ago).. i swapped a carb from a 1978 arrow and it fixed a ton of driveabilty issues.
    The carbs built pre-80's engine were the last of the leaded fuel, derestricted carbs that were aimed at making power. In this case that BJH is experiencing, the factory jets aren't the problem. There's an underlying problem that is causing it to run rich. Winding in the air idle circuit needle 'may' affect the mixture at idle but not across the whole rev range (start the engine, wind it in until the needle either seats or the engine conks out, then back it out 1/2 a turn at a time. Should be 1-1/2 to 1-3/4 turns max) This won't fix the problem if there's a vac leak somewhere, the O2 sensor is dead or the EGR valve is coked up.

  13. #13

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    bowl vent diaphragm

    071998_09.pdf

  14. #14

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    Thanks for the help internet people's. I'm just going to get a better carb and get rid of the old one. Too much of a hassle to be fiddling around with this carb.

    Edit: sorry for the late reply.

  15. #15



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    Quote Originally Posted by ikeepzitclean View Post
    bowl vent diaphragm

    071998_09.pdf
    Ooh, that may be relevant to my interests -- anyone know where to obtain a new bowl vent diaphragm these days?

  16. #16

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    Quote Originally Posted by SubGothius View Post
    Ooh, that may be relevant to my interests -- anyone know where to obtain a new bowl vent diaphragm these days?
    For an '87 engine with a Mikuni carb that has an electric choke, you want the bowl vent valve for sale in these listings:

    https://www.ebay.com/itm/TOMCO-7404-...Bsg:rk:52:pf:0

    https://www.ebay.com/itm/NOS-Tomco-7...O52g:rk:2:pf:0

    The listings and the manufacturer describe it as a choke pull-off valve, but that's incorrect. In both listings the pictured item is the bowl vent valve you need for that year and carb.

  17. #17



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    Thanks for that parts ref. I did the "blow into the bowl vent hose" test, which instantly killed a running engine and seemed to confirm the bowl vent issue for me, so I ordered a new one; however, I ran into issues starting to install it...

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