DYI01's street/kart track build
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DYI01's street/kart track build

This is a discussion on DYI01's street/kart track build within the Grom Builds forums, part of the Honda Grom Forums category; So I recently picked up a used 2015 for $2000 with 511 miles on the odometer. I looked for a while till this gem popped ...

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Thread: DYI01's street/kart track build

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    DYI01's street/kart track build

    So I recently picked up a used 2015 for $2000 with 511 miles on the odometer. I looked for a while till this gem popped up and drove about 165 miles each way to pick it up. It had a Vagabond fender eliminator kit, TST front flush mounts/electronic flasher relay, and some cheap Aprilia style mirrors. Besides those mods it was completely stock, hadn't even had the first service done. My plan for the Grom is to build it up to be a bike I can ride to my local Kart track, spend a few hours there, and ride back. The track is about a 10 minute ride from my house, so its super convenient. I can pack some snacks/drinks, a few tools, mini tire compressor, camping chair in a backpack, wear my track gear over there, remove the headlight/taillight/tag and be good to ride.

    It passed inspection without issue and I got the reg/tags/title/insurance all sorted out. The first thing I did was swap out the stock Vee Rubber tires for a pair of Pirelli Diablo scooter tires. I hadn't found many reviews of these tires but I figured I'd give them a shot. The literature on them makes it sound like they are just a downsized version of the Diablo Rosso Corsa 3 tires.





    Front tire profile


    Rear tire profile


    These things are miles better than the stock Vee Rubber which felt like I was riding on some Lego tires. The profile on the tires makes the Grom turn in really fast, and they hold a line pretty damn good. I feel like I can get on the brakes without fear of the Vee Rubber tire just washing out. It's a very confidence inspiring tire. I'll be able to give more feedback on the tires once I get some more miles on them, but initial impressions are very good.

    I wanted some lower and wider bars to be able to get down and off to the inside of the bike, and get a bit more weight on the front end. I ordered up a set of the ProTaper Honda Mini bars as they are lower/wider/and should hold up to a crash way better with the center brace. I topped them off with a pair of the Domino MotoGP grips.



    I went simple on the footpegs and went with a set of PSR's. I may go with a set of Driven or Woodcraft rearsets in the future, but these made a huge improvement in grip, which was my major gripe with the stock footpegs.



    Next on my list for track prep was getting some real suspension on the bike. I'm kind of a suspension snob and need a really tuneable suspension and have it setup correctly. I also ride an R6 with a full RaceTech setup and it's amazing. After doing lots of research I went with the Racing Bros fork kit and shock simply because of all the adjustability. For most people the Ohlins will probably be suitable as an upgrade in the forks, but I think it would drive me crazy not being able to tune it. The Racing Bros shock only adds a high speed compression damping circuit over the Ohlins, and its a good deal cheaper too.









    Fork tubes clamped in the vice using the Racing Bros foork tool.


    Heating up those fork lowers to soften up the threadlocker.


    Nasty crud between the lower and tube.


    Cleaned the crud off.


    Removing the spring cap off fork tube.



    Done installing the fork kit.


    Rear shock is a breeze to install.

    The suspension REALLY made a big difference to the Grom. Tires were a big jump, the forks and shock were a leap. The suspension doesn't just bottom out with me bouncing on it. With stock suspension at pace if you hit a mid corner bump, I felt like I was getting bounced off of my line. Now the suspension just moves and bumps barely upset the chassis. Under hard braking I could pretty much get the fork to almost bottom out, now there is actually support under hard braking, and I'm not afraid of bottom out, as we all know once the fork is bottomed out, the tire is the next thing to slide. This Grom is just a pleasure to ride around town, or in anger on the kart track. Next time when I service the forks I will use 10w oil as I'm close to the end of the adjustments on the forks using the recommended 7w oil.

    While I had the rear cowling off to install the rear shock, I went ahead and installed the new CustomLED BlasterX tail light and Targa fender eliminator kit. I know this is an aesthetic mod, but for me, it was more of a quick change setup for the track. Two nuts off the back of the tail light and the plug and it comes out. Two nuts and bolts for the tag and it comes off, and we all know how easily the headlight comes off.



    Part 2 in the next post.
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    Nice write up and pic, I like those shocks and front fork setup

    Ride safe and ride it like you stole it

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    OpusNectar's Avatar
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    Very nice start to your build!

    To get the most out of your rear shock setup, you'll want these: https://mnnthbx.com/product/mnnthbx-...or-honda-grom/

    Eliminates the bindings the stock rubber bushings cause. HUGE difference over stock.

    100% agree on the recommended 7W being too thin. I am almost all the way in on my rebound circuit.
    2015 Grom
    Koso 4V | Aracer AF1, DG1, MiniPlus2 | Kitaco Crank | Takegawa 5 Speed
    Kitaco CCT | Takegawa Oil Pump & 4th bearing | GF Billet Cam Cover
    34mm TB | MP Rev2 | PT CR High | Renthal Clamps
    Kitaco Clutch Cover & Oil Cooler | GF Speed Spacers
    Brembo 4P & P34 | BRAKING Rotors | Galfer SS Lines
    Driven TT Rearsets | OTB V2 Adjusters | MNNTHBX Swingarm Bushings
    RacingBrothers Sus. | Hindle High Mount | Saddlemen Seat | 428 conv. 15/36
    Mitas MC35S 100/120 | Gcraft Linear Damper Setup

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    After the suspension was done I spent some time getting a really good feel for it, tuning it and really getting it dialed in how I like it. I really wanted to see if there was a noticeable difference for when I swapped out the rubber swingarm bushings for the MNNTHBX bronze bushings. The install was straight forward, it took me a little time to figure out a simple way to get the rear wheel off the ground NOT using a rear stand. I basically just left the bike on the side stand, and leveraged the back wheel off the ground, and shoved a jackstand under the right side of the frame where the lower rear set bolt is. The installation with the bushing tool is cake, just follow the YouTube video instructions.








    I left the rear shock settings as I had used them on the stock bushings to see if there would be any difference in setup. Right off the bat I noticed how stiff the suspension felt and there was barely any sag with me sitting on it. This told me how much the stock bushings were causing the swingarm to bind and not want to move at all. Previously I had about an 35mm of sag setup and I was barely getting 10mm after the bushings. After taking about 2 full turns out of the preload adjuster, I got it back to around 35mm of sag again. The rebound and compression were also way stiff. The rear suspension definitely feels livelier and more active vs. the stock swingarm bushings. After spending some time tuning the Hi/Lo speed compression I was able to get it feeling plush on the harder hits like on potholes and bumpier roads, while be very supportive while cornering hard. These bushings are a "must do" mod IMO if you want the best suspension action out of your Grom.

    As you can see, I removed the stock exhaust when the swingarm came out for the MNNTHBX bushing install. Well I wasn't just going to put that heavy ass stock exhaust back on after I just took it off.




    Not the greatest scale, but it says the stock system weighs 11lbs.



    And the Yoshimura system weighs 5lbs.




    I love the sound this thing makes without the baffle in place, the baffle just makes it sound airy and farty, not so much quieter. I have a few videos of the exhaust, but there are so many Yoshimura exhaust videos on YouTube, I don't think we need anymore. The top end gain in power was noticeable, you can feel the power build a bit more and then kind of levels off vs. just falling right on its face after 6k rpm.

    I finally got around to safety wiring my oil fill cap and oil drain bolt for tech at the local track, they let it go the first few times, so I wanted to make I got it done before the next time I went. I installed the PSR oil fill cap and a generic magnetic oil drain plug. I did the first service on the bike cleaned a ton of crap out of the oil spinner and mesh screen. Checked the Valve clearances and they were on the tight end of spec, I'll check them again in about 700 miles when I plan on doing the next oil change. While I had the clutch cover bolts out, I also installed the TST Industries frame slider kit. It's a robust piece of kit and it bolts together perfectly, just follow the YouTube video tutorial and you wont go wrong. hopefully I wont have to test them lol.






    The next thing I wanted to address was the terrible headlight, I did a swap to a SF regulator/rectifier unit and H4 LED bulb. Made a huge difference in light output with no hit to the electrical system. I did a write up in the "How to guide" section of the forum for those interested in how to cleanly install the SF R/R without making a bracket AND still keep the rear brake reservoir in the stock location. The high beam indicator on the dash still works too.







    I'm currently working on the beginning stages of a stock airbox intake mod. I don't like any of the intake options on the market right now with the fairing rod support setup, not a fan of it at all. I took elements from a bunch of different airbox mods I had seen online. I don't think anyone has done an airbox mod quite like this. Once I get all the parts and figure out how it will all go together I'll post up about it. IMO when installing any intake system, that gets rid of the factory throttle body inlet tube, should be what I call velocity porting the throttle body. Using the stock throttle body without porting causes a ton of turbulence in the intake tract. I bought a used stock throttle body on eBay and did the port job on it. I started with a carbide single cut bit, a bastard cut file, then finished off with 180 grit sand paper. I may go smoother on the finish but not sure if the effort is worth the gain.




    Last edited by DYI01; 10-28-2019 at 11:48 AM.
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    Quote Originally Posted by OpusNectar View Post
    Very nice start to your build!

    To get the most out of your rear shock setup, you'll want these: https://mnnthbx.com/product/mnnthbx-...or-honda-grom/

    Eliminates the bindings the stock rubber bushings cause. HUGE difference over stock.

    100% agree on the recommended 7W being too thin. I am almost all the way in on my rebound circuit.
    Already ahead of you chief!

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    Quote Originally Posted by DYI01 View Post
    I'm currently working on the beginning stages of a stock airbox intake mod. I don't like any of the intake options on the market right now with the fairing rod support setup, not a fan of it at all. I took elements from a bunch of different airbox mods I had seen online. I don't think anyone has done an airbox mod quite like this. Once I get all the parts and figure out how it will all go together I'll post up about it. IMO when installing any intake system, that gets rid of the factory throttle body inlet tube, should be what I call velocity porting the throttle body. Using the stock throttle body without porting causes a ton of turbulence in the intake tract. I bought a used stock throttle body on eBay and did the port job on it. I started with a carbide single cut bit, a bastard cut file, then finished off with 180 grit sand paper. I may go smoother on the finish but not sure if the effort is worth the gain.




    Lookn good man, You are definitley off to a good start... Awseome porting of your TB, dont forget the intake manifold and isolator. A big fan of DIY airbox mods, cant wait to see what you've come up with
    Super!Stock 2018 DSR Honda Grom

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    Takgawa Hi Ign Coil w/NGK Cable
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    Galfer Disk Wave Rotors and pads
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    Ohlin Fork Springs Ohlin HO 424 Rear Shock
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    Quote Originally Posted by dubSolo View Post
    Lookn good man, You are definitley off to a good start... Awseome porting of your TB, dont forget the intake manifold and isolator. A big fan of DIY airbox mods, cant wait to see what you've come up with
    The stock manifold entry and the throttle body exit look to be pretty close in diameter, if anything, the manifold is a tad larger. The manifold exit is definitely way smaller than the isolator. I haven't measured the cylinder head intake port but that seems to also be really small. I have a used head on the way that I am going to have some light port work done to, mostly just port matching the entire intake and exhaust tract. It will likely get a valvetrain upgrade and definitely a camshaft upgrade. But I'm not looking to go any further on the engine than the top end at the moment. Looking at brake upgrades at the moment, thinking about the Brembo p2 34 front caliper upgrade and just doing a line and pad for the rear.

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    Quote Originally Posted by DYI01 View Post
    The stock manifold entry and the throttle body exit look to be pretty close in diameter, if anything, the manifold is a tad larger. The manifold exit is definitely way smaller than the isolator. I haven't measured the cylinder head intake port but that seems to also be really small. I have a used head on the way that I am going to have some light port work done to, mostly just port matching the entire intake and exhaust tract. It will likely get a valvetrain upgrade and definitely a camshaft upgrade. But I'm not looking to go any further on the engine than the top end at the moment. Looking at brake upgrades at the moment, thinking about the Brembo p2 34 front caliper upgrade and just doing a line and pad for the rear.
    Carpimoto is still running their sale on P4 calipers

    https://www.carpimoto.com/en-US/4240...embo-P4-30.htm

    Stock master works very well with this caliper. Night and day leap in performance.
    2015 Grom
    Koso 4V | Aracer AF1, DG1, MiniPlus2 | Kitaco Crank | Takegawa 5 Speed
    Kitaco CCT | Takegawa Oil Pump & 4th bearing | GF Billet Cam Cover
    34mm TB | MP Rev2 | PT CR High | Renthal Clamps
    Kitaco Clutch Cover & Oil Cooler | GF Speed Spacers
    Brembo 4P & P34 | BRAKING Rotors | Galfer SS Lines
    Driven TT Rearsets | OTB V2 Adjusters | MNNTHBX Swingarm Bushings
    RacingBrothers Sus. | Hindle High Mount | Saddlemen Seat | 428 conv. 15/36
    Mitas MC35S 100/120 | Gcraft Linear Damper Setup

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    Quote Originally Posted by OpusNectar View Post
    Carpimoto is still running their sale on P4 calipers

    https://www.carpimoto.com/en-US/4240...embo-P4-30.htm

    Stock master works very well with this caliper. Night and day leap in performance.
    I thought about the P4 calipers, but the fact you need to remove the rotors from the wheel every time you want to remove the wheel or calipers was a huge turn off for me. I'm thinking the P2-34 will be a great upgrade long with a SS line and the better pad compound in the P2. I'm not really big on using the rear brake much during normal riding. I use it mostly when braking really hard to settle the chassis. I'm thinking a line and pad upgrade will suffice.

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    Spent a few hours at the local kart track today and brought along my GoPro. I need to record more when on track as I can see where i'm taking shit lines and where I can improve.





    Shredded these tires pretty good on the track


    Last edited by DYI01; 10-27-2019 at 11:32 AM.

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