How to: ND4's fork upgrade mod.... 15 bucks, worlds better!
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How to: ND4's fork upgrade mod.... 15 bucks, worlds better!

This is a discussion on How to: ND4's fork upgrade mod.... 15 bucks, worlds better! within the Grom How-To's and Guides forums, part of the Honda Grom Forums category; NOTE: This does not work on the 2nd gen groms as they have different fork caps. If anyone needs these parts PM me, I can ...

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Thread: How to: ND4's fork upgrade mod.... 15 bucks, worlds better!

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    How to: ND4's fork upgrade mod.... 15 bucks, worlds better!

    NOTE: This does not work on the 2nd gen groms as they have different fork caps.

    If anyone needs these parts PM me, I can get them to you for ~15 bucks shipped.



    Alright, as we all know the stock forks are super soft, bottom out stupid easy and dont have much travel.

    So after looking at options from racetech, ohlins etc and looking at how the forks were built i was like... hmm i dont feel like dropping 300+ bucks for fork upgrades, but id like to do something about it. So i purchased some 20wt oil, but while that was coming in the mail i decided to take it one step further, Get me some more suspension travel.

    On the grom front forks this is actually REALLY easy and can be done CHEAP, im talking 5 bucks in parts at the hardware store. Essentially i made the internal damper rod 1inch longer via a 1inch long steel spacer to move the top of the rod down one inch. This is not adding preload to the spring, but increasing overall travel (similar to the racetech fork upgrades and how they are 20mm longer than stock). Personally i like the soft springs as they provide a nice ride and i do a good amount of off roading as well... so this mod has a twofold benefit as i get ground clearance, more suspension travel etc.

    Here are the stock top cap internals taken apart
    How to: ND4's fork upgrade mod.... 15 bucks, worlds better!-img_20160116_134643.jpg

    And stock top cap internals stacked together as they come out. Note that the damper rod goes through the center and there is a lil cir clip on the rod that holds the big washer you see from sliding down the rod.
    How to: ND4's fork upgrade mod.... 15 bucks, worlds better!-img_20160116_134734.jpg

    Below are the parts I used for the spacer. The row at the top are parts I bought at the hardware store. An M8 x 50mm long cap head bolt, a 1inch long spacer that just so happened to be the perfect size (same OD as the damper rod ~ 12mm), 2 small thin 1/2in ID rubber washers to take up some space, and a small OD M8 washer to hold the stock bottom out washer in place (this was the job of the small circlip previously)
    How to: ND4's fork upgrade mod.... 15 bucks, worlds better!-img_20160116_135202.jpg

    Here is the spacer seated in the stock top cap
    How to: ND4's fork upgrade mod.... 15 bucks, worlds better!-img_20160116_135218.jpg

    Here is the stock rubber bottom out bumper over the new spacer (2 thin rubber washers went between the top cap and stock rubber bumper). Note how there is a little extra of the spacer sticking out. The stock bottom out washer slides over this and gets held in place by the M8 washer purchased above)
    How to: ND4's fork upgrade mod.... 15 bucks, worlds better!-img_20160116_135329.jpg

    And this is the final product that gets screwed back on the damper rod. Yes the silver M8 washer is much larger than the stock circlip used to hold the bottom out washer, but its not an issue, the inner diameter of the stock lower fork tube that this assembly goes down into is PLENTY big enough for this washer to clear. In essence the spacer and silver m8 washer are sandwiched between the stock top cap and the top of the stock damper rod.

    How to: ND4's fork upgrade mod.... 15 bucks, worlds better!-img_20160116_135411.jpg

    While i was doing this mod, I also changed out the fork oil to 20wt maxima fork oil at the recommended height (YOU CAN NOT increase oil height by much at all!!!!, after some measurements and experimenting with oil height, stick with the stock 75mm of oil height. Going taller makes it to where there is no room for air when the fork is compressed... NOT GOOD!)



    Overall impressions.... HOLLY SHIT, WORLDS better, I had to TRY to make it bottom out now, places where it would bottom out before didnt even come close.

    For 15 bucks (10 for fork oil, 5 in parts from the hardware store) I could not be happier with the results!!

    Feel free to ask questions.

    Quote Originally Posted by nd4spdbh View Post
    FYI here are the quantities hillman part numbers and description if anyone wants

    Quantity - part-number - description

    2x - 59363-F - 1in Spacer (5/16ID - .469in OD - 1in Long)
    4x - 3815-F - Neoprene washer (7/16ID - 1in OD)
    2x - 43110-N - M8x50 1.25 pitch bolt
    2x - 43893-E - Small M8 Washer
    Quote Originally Posted by nd4spdbh View Post
    Here you go.
    From left to right with quantity needed. 1. Steel spacer 2x, 2. Rubber washer 4x, 3. Longer bolts 2x, 4. Small OD m8 washer 2x.

    These are all Hillman Fasteners brand part numbers.

    Attachment 26630Attachment 26631Attachment 26632Attachment 26633
    Here are the part numbers used.


    Quote Originally Posted by Epic Trekker View Post
    Thank you nd4spdbh!!! What a deal to change the uber poor performance of those stock forks! I didn't do the 20wt yet (couldn't wait, but oh what a difference. Here's how I did the mod, hope I did it right:


    Sent from my SM-T230NU using Tapatalk
    Quote Originally Posted by jzehren11 View Post


    Decided to make a video of us doing this mod! What a huge difference!
    Last edited by nd4spdbh; 10-19-2017 at 10:36 AM.

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    Awesome write up! I'm thinking of switching to springs with the proper rate for my weight but I'm now really interested in doing this. Does this change the geometry of the bike at all? Like does it make the front end higher?

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    Quote Originally Posted by brendon View Post
    Awesome write up! I'm thinking of switching to springs with the proper rate for my weight but I'm now really interested in doing this. Does this change the geometry of the bike at all? Like does it make the front end higher?
    It raises the front of the bike by 1 inch, exactly the same amount as the spacer added. This will increase rake a little. I think someone else did the measurements and its around 1-1.2*, this should make the bike a little more stable at speed at the sacrafice of every so slightly harder turn in. Neither of those are likely felt much.

    After doing some more riding with the spacer setup and thicker oil, its worlds freaking better. The extra inch of uptravel actually allows the stock valving to work in the thicker oil SO MUCH BETTER. I use to bottom out hard on the bottom out washer at the top cap all the time with the original fork setup and all that is nearly gone now.
    Epic Trekker and ikeus685 like this.

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    What is the stock oil weight and can you go even thicker without hurting the valves, say 30?

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    Quote Originally Posted by keit29 View Post
    What is the stock oil weight and can you go even thicker without hurting the valves, say 30?
    Stock oil weight is 5 or 10wt. Honestly i wouldnt go above 20 as then you might get into the realm of the suspension not being able to keep the tire on the ground properly (suspension moves too slow). 20wt with the extra fork height seems to work very well. That stated i am light, 160lbs.

    Some have gone to 30wt however and have reported good results!

    You can always give it a try, its 10 bucks for a quart of fork oil.
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    I'm a good 230lbs after a poop. So I need some beefier shocks.
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    Great mod - need to stop by the hardware store I think. Looking at the stock exploded diagram, am I right that the damper rod just rests on the little tapered bolt in your first picture? I'm 6ft 200lbs and the bottom out and brake dive is getting pretty old, this looks like a perfect solution without having to drop massive money on springs.

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    Quote Originally Posted by bostonbacon View Post
    Great mod - need to stop by the hardware store I think. Looking at the stock exploded diagram, am I right that the damper rod just rests on the little tapered bolt in your first picture? I'm 6ft 200lbs and the bottom out and brake dive is getting pretty old, this looks like a perfect solution without having to drop massive money on springs.
    The weight of the front is supported by the cap that are held by that tapered screw.

    I should of added as well, that when the fork bottoms it bottoms out on the big washer n rubber bumper (also supported by the top cap)
    Last edited by nd4spdbh; 01-24-2016 at 10:10 PM.
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    Quote Originally Posted by nd4spdbh View Post
    The weight of the front is supported by the cap that are held by that tapered screw.

    I should of added as well, that when the fork bottoms it bottoms out on the big washer n rubber bumper (also supported by the top cap)
    Got it! Thanks for the info. Looking forward to doing this once the weather warms up a bit and I can work in the driveway without my fingers turning into icicles.

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    Quote Originally Posted by bostonbacon View Post
    Got it! Thanks for the info. Looking forward to doing this once the weather warms up a bit and I can work in the driveway without my fingers turning into icicles.
    Obviously this how two is at your own risk, I did measurements and tests and the 1inch spacer should work without issue. I did make sure that i filled the forks with the proper amount of oil so as not to run out of room when the suspension cycles.

    Did some more riding on the grom today including some off roading, never bottomed once!

    How to: ND4's fork upgrade mod.... 15 bucks, worlds better!-today.jpg

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