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Grom build

  1. #1
    Unsafe At Any Speeds Jim's Avatar
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    Grom build

    Marks R7 thread, and Jamesí threads over the years have inspired me to make one of my own.

    Been track riding since 2009 and racing since 2011. Two years ago, I finally picked up my first pit bike. Unfortunately no one warned me about the obsession over modifying Groms.

    Apologize for using pics from Instagram. Itís all I had in my phone.


    Picked this up and had it delivered via Uship to NJMP on a race weekend



    Fork seals were blown and forks had no oil. So good opportunity to upgrade. Ohlins fork internals installed










    Reached out to the exhaust vendor to get mounting hardware. Bike was using zip ties and wasnít doing its job.




    The rear tire had a nail in it and was totally worn to the cords. So new tires, installed at NHMS.



    Ditched the airbox and installed something easier to service.



    Upgraded the cam and a flashed ECU. This bumps the rev limiter from 8k to 10k.






    Next was the high flow oil pump, 60% clutch springs, and billet clutch plate. For anyone that knows Honda single cylinder engines, they use an oil spinner to cool everything down and no oil filter. The clutch cover available for these bikes removed the oil spinner (2.5 pounds of rotating mass off the crank) and adds an OEM Honda oil filter.





    The OEM chain spacers are garbage and I wanted spools.





    The bike was used for MiniGP racing so it had -1/+4 gearing. Dropped down a tooth to go +3 and installed a new DID 420 chain. Since I hate clip master links, I safety wired and covered it in silicone.



    Now this is a function mod. Riding in the pits when the ground is wet, my back gets soaked. This $30 piece of plastic from Amazon was well worth it.


    The rear shock was actually a fake replica. The adjuster knobs werenít actually knobs and just pieces of plastic on the shock. Also had no oil in there. Note the difference in length on the new Ohlins.


    The exhaust can was rattling inside. Got a replacement with new minting hardware.



    Brembo RCS14 master cylinder. Motion Pro Rev3 throttle kit. The new Rev3 has a super short reel.




    Up next is the NEO 181cc 2v motor kit. This is a complete kit with the crank, head, gaskets, cam, and even included the spark plug.

    Piston, crank and internals have been WPC treated. Crank was welded and balanced. Head was ported and polished. Also going with the 5-speed transmission. This motor kit is just as reliable (if not better) than the OEM motor. Horsepower on these kits will triple the horsepower from 8hp to 23-24hp on 93 pump gas.

    Big gotcha is all the other required components. So with the engine build is also:
    - oil cooler
    - bigger fuel injector
    - bigger throttle bodies
    - bigger starter
    - bigger battery
    - oil catch can
    - aRacer ECU and tuning
    - 4th bearing kit to support the crank
    - upgraded chain tensioners

    Because I want to monitor temp, I went with the Koso dash. Totally programmable and had a gear indicator too. Can set your RPM range, red line, and shift light. So itíll be set properly after a dyno run.




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    Last edited by Jim; 06-05-23 at 09:37 AM.
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  2. #2
    TWINS! xrocket21's Avatar
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    Re: Grom build

    Sick build! Getting real deep into it!

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  3. #3
    Lifer nt650hawk's Avatar
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    Re: Grom build

    You'll never use all that Grom!

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    Gino
    HAWK GT Racer Expert #929
    2012 CCS LRRS ULSB Champion
    2012 CCS LRRS P89 Champion
    2008 CCS ULSB National Champion
    ECKRACING Bridgestone Street & Competition Woodcraft MOTUL On Track Media Pine Motorparts Vanson Leathers

  4. #4

    Re: Grom build

    Oh. You've done A LOT.

    I've had mine since pre order in 2014 if I recall and I've done nothing in comparison!

    Grom build-gromcapture-jpg

    How fast does yours goes with the spinner removal? I can typically maintain 60/65 stock gearing. Can get into 70's downhill and drafting.

    Following

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  5. #5
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    Re: Grom build

    DAM! Nice work, that's a Lot O parts.....

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  6. #6
    ....................... PinHead's Avatar
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    Re: Grom build

    Holy smokes!

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    2018 Harley Road Glide
    2000 Ducati 900ss
    2003 Harley Softail Deuce

  7. #7
    Angry Gumball RandyO's Avatar
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    Re: Grom build

    I'll race ya with my K-Pipe

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    RandyO
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  8. #8
    Unsafe At Any Speeds Jim's Avatar
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    Re: Grom build

    Quote Originally Posted by Vovchandr View Post
    Oh. You've done A LOT.

    I've had mine since pre order in 2014 if I recall and I've done nothing in comparison!

    How fast does yours goes with the spinner removal? I can typically maintain 60/65 stock gearing. Can get into 70's downhill and drafting.

    Following
    spinner just makes it rev up quicker and doesnt impact top speed. i hit 69 MPH downhill with -1/+3 gearing right now, and i have a device that corrects the speedo error with the gearing changes. the new dash i bought allows you to enter your gearing there and it'll make its adjustments.
    stock gearing i think is 15/34. with the NEO, i'll be using 17/43

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  9. #9
    Being A Dick PurplePackage's Avatar
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    Re: Grom build

    I have a red lower cowl piece somewhere if you're interested in putting one on. I'm sure it isn't OEM.

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  10. #10
    Awesomeness, Inc. MattR302's Avatar
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    Re: Grom build


    There’s a couple companies that make kits to swap in the CBR250/CBR300 motor, if you want a low-stress 24/30 hp with only a ~40lb weight penalty

    My Monkey has almost 7k on it, almost all from the previous owner. I have a spinner delete clutch cover waiting for the next oil change, but I’m trying to resist the temptation to do any performance stuff to it.

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  11. #11
    Lifer OneCheekRider's Avatar
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    Re: Grom build

    Very cool build! I have a love/hate relationship with my z125 and keep contemplating throwing parts at it or selling it. It's been stock since I bought it with 40miles on it.

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  12. #12
    Unsafe At Any Speeds Jim's Avatar
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    Re: Grom build

    Quote Originally Posted by MattR302 View Post

    There’s a couple companies that make kits to swap in the CBR250/CBR300 motor, if you want a low-stress 24/30 hp with only a ~40lb weight penalty .
    there's a guy that put a turbo on his swapped CBR300 motor. only thing is, it's not really a Grom at that point

    - - - Updated - - -

    Vortex 34 rear sprocket and Shorai battery just arrived.

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  13. #13
    Unsafe At Any Speeds Jim's Avatar
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    Re: Grom build

    Quote Originally Posted by OneCheekRider View Post
    Very cool build! I have a love/hate relationship with my z125 and keep contemplating throwing parts at it or selling it. It's been stock since I bought it with 40miles on it.
    there isnt much in the aftermarket world for the Z125 compared to the Grom. I did do an Ohlins fork valve kit on one in my garage. they're easier to get off the bike compared to a Grom but slightly more work to service

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  14. #14
    Angry Gumball RandyO's Avatar
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    Re: Grom build

    Quote Originally Posted by Jim View Post
    there isnt much in the aftermarket world for the Z125 compared to the Grom. I did do an Ohlins fork valve kit on one in my garage. they're easier to get off the bike compared to a Grom but slightly more work to service
    I didn't think there was much aftermarket for my K-Pipe either... till I discovered the performance pit bike market, there is a ton

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    RandyO
    IBA#9560
    A man with a gun is a citizen
    A man without a gun is a subject LETS GO BRANDON

  15. #15
    Unsafe At Any Speeds Jim's Avatar
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    Re: Grom build

    Just picked it up from one of the more known Grom builders in the US. This bike rips!

    Say hello to 24hp on a 2 valve




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  16. #16
    Unsafe At Any Speeds Jim's Avatar
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    Re: Grom build

    NEO 181cc kit: crank, piston, head
    head sent out for port and polish
    crank welded and balanced
    ported throttle body spacers
    manual cam chain tensioner
    titanium valve spring retainers
    brass throttle body screw
    big 34mm throttle body
    crank and motor internals WPC coated
    PCX150 10-pin fuel injector
    high flow oil pump
    cam
    4th bearing crank support
    upgraded starter
    upgraded lithium battery
    7 row oil cooler
    aRacer ECU and AF2

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  17. #17
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    Re: Grom build

    So, guessing this will be around for a while?!? I can never sell something once I customize it this much.

    ENJOY IT!!

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  18. #18
    TWINS! xrocket21's Avatar
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    Re: Grom build

    Does it even wheelie?

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  19. #19
    Your Father csmutty's Avatar
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    Re: Grom build

    I want a head to head race with your gixxah. I think the grom will win.

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    -Christian LRRS/CCS HasBeen ECK Racing
    2011 Pit Bike Race CHAMPION!

  20. #20
    Unsafe At Any Speeds Jim's Avatar
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    Re: Grom build

    Quote Originally Posted by xrocket21 View Post
    Does it even wheelie?
    Still doing the break in, but I was told it will lift around 6500 RPM at WOT


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  21. #21
    Unsafe At Any Speeds Jim's Avatar
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    Re: Grom build

    Koso dash installed. This is before the adapter plate from The Ruck Shop to utilize the factory headlight fairing




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  22. #22
    Unsafe At Any Speeds Jim's Avatar
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    Re: Grom build

    After the adapter plate from The Ruck Shop to fit the Koso dash. OEM cowl installed.




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  23. #23
    Unsafe At Any Speeds Jim's Avatar
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    Re: Grom build




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  24. #24
    Unsafe At Any Speeds Jim's Avatar
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    Re: Grom build

    Oil cooler and NEO head




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  25. #25
    Unsafe At Any Speeds Jim's Avatar
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    Re: Grom build




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