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DIY throttle body butterfly install and port?

This is a discussion on DIY throttle body butterfly install and port? within the Grom Performance forums, part of the Honda Grom Garage category; Ive spent quite a lot of time trying to figure out if anyone has attempted to install a larger TB butterfly into their stock TB ...

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    MotoTG26's Avatar
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    DIY throttle body butterfly install and port?

    Ive spent quite a lot of time trying to figure out if anyone has attempted to install a larger TB butterfly into their stock TB and cant seem to find any information.

    is this even possible? i want to attempt this. porting the TB isnt an issue for me, but I need to find some how to's on butterfly replacement.

    idk if im just not searching the correct terms or what but i cant seem to find anything.

    can anyone help a fellow grommer out??

    i spoke with Monkey Father today and we have both came to the conclusion that my stock TB may be bottlenecking my set up.

    even if i fail miserably, it wont cost me much but time. im trying to get to 26mm. right now im running the finbro head with matching 25mm inlet, koso 170cc bbk with cam, chimera intake, pro circuit exhaust, api tech efi. 1st-3rd gear is amazing, but im having issues with 4th gear and its my belief i may not be getting enough air

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    a_morti's Avatar
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    If you've taken monkey fathers time getting that advice I think it would be the decent thing to do to buy his bigger throttle body kit. Otherwise you're looking at trying to bore a 24(?) hole out to 26, on a perfect centre without wrecking it. If you don't get it centred it won't seal when you close the throttle. Most people can't use a mill that accurately. Most people including me don't have access to a mill at all.
    gromhawk likes this.

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    Can you? Yes, is it worth your time? No

    boring the TB and installing a larger butterfly is what MonkeyFather does, just spend the coin and save yourself the trouble

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    damnit thats what i was affraid of, im trying to limit my spending at this point

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    As someone said before me- it can be done. However I seriously doubt that it would worth the effort.
    Depending on the size you'd want to end up one can buy either PCX 150 TB (26.4mm) or a cbr125 TB (31mm) from a salvaged bike. Pre 2015 PCX has single cable throttle, later ones double wired. I've seen healthy 31M CBR units on fleabay for less than 20GBP including the sensors and injector.
    Heck that is what I call value for money.

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    Better off buying one.

    here is a stock one bored.
    https://www.steadygarage.com/store/c...honda-grom-125

    or the new koso one
    https://www.steadygarage.com/store/k...honda-grom-125
    Follow me @longballer on instagram.
    FrankenStein Build thread

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    Quote Originally Posted by MotoTG26 View Post
    Ive spent quite a lot of time trying to figure out if anyone has attempted to install a larger TB butterfly into their stock TB and cant seem to find any information.

    is this even possible? i want to attempt this. porting the TB isnt an issue for me, but I need to find some how to's on butterfly replacement.

    idk if im just not searching the correct terms or what but i cant seem to find anything.

    can anyone help a fellow grommer out??

    i spoke with Monkey Father today and we have both came to the conclusion that my stock TB may be bottlenecking my set up.

    even if i fail miserably, it wont cost me much but time. im trying to get to 26mm. right now im running the finbro head with matching 25mm inlet, koso 170cc bbk with cam, chimera intake, pro circuit exhaust, api tech efi. 1st-3rd gear is amazing, but im having issues with 4th gear and its my belief i may not be getting enough air
    What motor are you using, stock OEM motor
    BBK 183 finbro with the heads and Port/polish inlet pipe.

    Since we do not know what engine and mod you have I'll take a stab at what you need.
    Bigger port/polish inlet pipe with matching 27mm plastic spacer. The stock OEM throttle body works great with the bigger inlet pipe and bigger better F/I
    PC-150 F/I or Finbro 6 hole type 2 F/I
    full exhaust system and matching airbox mod or upgrade.
    Good map if you are using a PCV-WB02 unit.
    Good cam

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    here shortly ill be running the full blown finbro 183cc bbk. i have his head with bigger valves etc, and his inlet bored out to 25mm. i have the koso cam but may be upgrading to the DCR, idk yet. Chimera intake. i do have dual crower dual valve springs as well. pro circuit full exhaust, and finbros api with his map. aem guage with wideband o2, opmid temp guage, ohlins suspension, most of the bike is now carbon fiber with protaper honda mini bars. so basically the only thing that is stock is the TB itself

    i ended up seizing my 170cc bbk last night due to my own stupidity and frustrations, but thats another story for another time.

    hard racing is sending me everything i need to have the full blown finbro bbk, i just placed the order today

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    Quote Originally Posted by MotoTG26 View Post
    here shortly ill be running the full blown finbro 183cc bbk. i have his head with bigger valves etc, and his inlet bored out to 25mm. i have the koso cam but may be upgrading to the DCR, idk yet. Chimera intake. i do have dual crower dual valve springs as well. pro circuit full exhaust, and finbros api with his map. aem guage with wideband o2, opmid temp guage, ohlins suspension, most of the bike is now carbon fiber with protaper honda mini bars. so basically the only thing that is stock is the TB itself

    i ended up seizing my 170cc bbk last night due to my own stupidity and frustrations, but thats another story for another time.

    hard racing is sending me everything i need to have the full blown finbro bbk, i just placed the order today
    How'd you seize up the motor? Did you have to cut valve reliefs in the piston to run the Finbro head with larger valves?

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    What 170cc kit did you seize, by any chance a BrianS 170? If it is a BrianS 170 do you have his ported head with the duel Crower valve springs and valve stem caps? PM me if you do.

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