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Thread: Jet size help

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  1. #1 Jet size help 
    C-Moto Regular
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    HI there i have a apache 125. Its got a sports exhaust on it aswell as a cone filter. I was wondering if anyone knows what size jet i should running it on with these little mods. I was running a 98 but the bike didnt want to run aswell as it should. So ive just brought a 105 and still cant it running right but need to spend more time on it. Any advice would be greatly appreciated. Thanks
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  2. #2 Re: Jet size help 
    C-Moto Guru
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    Did you also rise the needle too?
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  3. #3 Re: Jet size help 
    C-Moto Regular
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    Ah no I didint. How do you do that. And thanks for reply mate
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  4. #4 Re: Jet size help 
    C-Moto Noob
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    small washers 1mm and keep starting and checking after each one to see how it runs some bikes have clips to raise them depending on carby.

    youtube carby needle mods theres a few on there.
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  5. #5 Re: Jet size help 
    C-Moto Guru
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    Check this video for example (your carburetor is probably more like the second one they show):


    In your case you'd most probably need more rich mixture, so put the clip on the lowest position and see if gets better. If not, you might need a bigger main/slow jet. Or a leaner mixture.

    Keep in mind that needle position affects mainly throttle response.
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  6. #6 Re: Jet size help 
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    the bike is getting to 6-8000 rpm and then it stutters. Ive tried making the mixture more rich and lean but doesnt help at all/ Any clue
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  7. #7 Re: Jet size help 
    Senior C-Moto Guru ZMC888's Avatar
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    Quote Originally Posted by Bradleyrayner View Post
    the bike is getting to 6-8000 rpm and then it stutters. Ive tried making the mixture more rich and lean but doesnt help at all/ Any clue
    The idle jet adjust screw only does idle. The main jet only does the main torque mid range powerband so you need to lift the needle a few mms to let in more fuel for the bike to run rich enough at high revs if your carb is a needle type.
    Put in a new spark plug, run the bike at 8000 rpm and then hit the kill switch, pull the plug out if it's whiteish on the electrode it's running too lean. Probably why it's stuttering too lean at high rpms.

    Hope this helps!
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