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carb rejetting for aftermarket intake exhaust and altitude

Discussion in 'XJ Modifications' started by gitsum911, Dec 9, 2012.

  1. gitsum911

    gitsum911 Member

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    so i have a question on what jets i need to put into my mikuni bs28 carbs. i have pod filters opened up exhaust and live in central utah at about 4600 feet above see level. i know that the bike used to live in oregon but i have no clue if its ever been rejetted or not and the #'s on the mains look like they say 110.... dont know if this is even correct or not. but if anyone has any suggestions for me that would be awesome, and p.s. i dont no anything about actually puttin them in to see if there the right size so any info would help. thanx guys Justin
     
    gitsum911, Dec 9, 2012
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  2. RickCoMatic

    RickCoMatic Well-Known Member

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    Here's the BEST advice your likely to get for your particular situation.

    Before you attempt to Tune the Bike for the MODS, ... acquire an AirBox and Boots and Fine Tune it to the Hairy-edge of Stock.

    Once you have the Bike running very well, ... then experiment with the PODS and Re-jetting.

    If your Exhaust is Straight Pipes with No Back Pressure, ... you might NEED a Universal Baffle added to provide a modicum of Back Pressure to alleviate a Lean Condition prevalent with Headers into Straight-throughs.

    Once you have it Dialed-in -- Stock Intake -- you will have a State of Tuning you my easily return to if the experimental Tuning for MODS becomes extraordinarily frustrating.
     
    RickCoMatic, Dec 9, 2012
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  3. gitsum911

    gitsum911 Member

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    ok thats a good suggestion but my problem with that would be my frame is totally reworked cause i bobbed my bike and now all my electronics are in place where the air box would go... so any other ideas maybe? as for my exhaust its cut off right where the mufflers went and i put on about 18 inches of 2" strait pipe. i can say when the bike was stock intake and exhaust it ran like a raped ape lol
     
    gitsum911, Dec 9, 2012
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  4. RickCoMatic

    RickCoMatic Well-Known Member

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    Go back to the Drawing Board.
    Re-Fab.
    Return to Raped-Ape status.
     
    RickCoMatic, Dec 9, 2012
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  5. gitsum911

    gitsum911 Member

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    Re: carb rejetting for aftermarket intake exhaust and altitu

    Lol ok ill see what i gotta do. Thanx for the suggestions
     
    gitsum911, Dec 9, 2012
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  6. Ted

    Ted Member

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    Re: carb rejetting for aftermarket intake exhaust and altitu

    RickCoMatic is right, it's always best to get it running properly before getting crazy with the mods, but here's the answer you were looking for:

    http://xjbikes.com/Forums/viewtopic/t=36972.html

    I found this for you just using the search function. It's got a pretty good step-by-step in there for determining a starting point on jet sizes. Every bike is different so there's never a sure-fire answer but this will get you started.

    BTW, I just ordered some jets here:

    http://jetsrus.com/

    Great prices but I can't vouch for their service yet. They also have some good info about tuning and re-jetting if you click on the "FAQ/Tuning/Video" link at the top of the page.
     
    Ted, Dec 9, 2012
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  7. gitsum911

    gitsum911 Member

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    Hey thanx i actually came across that also and determined that i gotta go to 112.5 on my mains and #41 on my pilots. And i also came across jetsrus.com today also haha great minds think alike dude and thanx for the help
     
    gitsum911, Dec 9, 2012
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  8. Ted

    Ted Member

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    FYI, I would run through the formula to help you find the right jet size to start with but I don't know what your bike is... helps a lot if you add it to your signature! :wink:
     
    Ted, Dec 9, 2012
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  9. gitsum911

    gitsum911 Member

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    Cool but i dont have a clue how to mess with my sig as of now ill have to do it on a desktop instead of my phone but btw i also found out my carbs are Hitachi and not mikuni so sorry bout the confusion and also my bike is an 82 xj650 bobber. Wish i could post pics cause the bike is sick
     
    gitsum911, Dec 9, 2012
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  10. gitsum911

    gitsum911 Member

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    I think i got my sig fixed..... i hope
     
    gitsum911, Dec 9, 2012
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  11. gitsum911

    gitsum911 Member

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    ok i was able to get one pic up in my gallery
     
    gitsum911, Dec 9, 2012
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