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Discussion Starter · #1 ·
Okay, here we go... This mod is intended to improve three things, throttle response, quicker acceleration and more mph. You should notice instant throttle response improvement throughout the rpm range from idle to redline and quicker revs/mph from 20 mph and above.


Tools needed: 5mm allen, phillips screw driver, drill w/step bit, grinder or razor blade.

1. Remove left side tank shroud, I removed both sides for convenience.


2. Remove airbox cover, 8 phillips screws. Remove air filter, 1 phillips screw. I didn't take a pic of the air filter, what you'll find is a back fire screen on the back of the filter. Remove it by grinding the 4 plastic nubs or slicing through them with a razor.

Behind the air filter you'll see the intake tube to the throttle body, it's designed by Honda to have flow restriction without a restriction plate by being tucked into the corner of the air box. Look closely and you'll see that it's actually a two piece tube with a restrictive coupling joining the two pieces together. Remove the short tube and coupling, pull apart the hose and cut the two plastic nubs holding the metal bracket. Re-install the air filter and air box cover.



3. On the top left side of the air box you'll see the inlet air tube facing rearward (first pic). Disconnect the gas tank breather, grab the base of the inlet tube and rotate it 180 degrees, re-attach tank breather hose on inside of inlet (second pic).


4. Left side inner shroud, take your drill and step bit and drill six 1/2" holes in the two middle vent slots(or cut how you see fit). Your airbox inlet tube lines up perfectly behind these two vent slots. Those of you who are worried about rain... No Worries bc the inlet tube sits far enough back from the vent holes.




5. Re-install your panels, go for a ride and notice the diff. This mod will work even better when you upgrade your oem paper filter for an aftermarket foam.


Enjoy and hope this thread helps.
 

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I should mention... part throttle acceleration was noticeably improved from my similar mods, but full throttle acceleration was fairly similar. Full throttle stock though the bike started to drop in power around 8,000rpm. Now it carries smoothly to redline. This definitely helps free up the upper RPM power and part throttle torque.
 

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Wicked mod! Nice of you to even share that with us. Thanks man. Did you notice any difference in the suction sounds?
 

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Hells yes! Hopefully I have time to do this one today! Have to swing by Lowe's and get some of those step bits first...

Anyone know if there's a foam filter, or a K&N or something, for the Grom yet?
 

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Hells yes! Hopefully I have time to do this one today! Have to swing by Lowe's and get some of those step bits first...

Anyone know if there's a foam filter, or a K&N or something, for the Grom yet?
I've read it's a similar filter to the 250R but I haven't confirmed that myself yet. Do a search on the forum and I think you'll find the post about that. If so, then yes the K&N would be available already. If not I'm sure one will be out soon.
 

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very cool mod. rain would be an issue where I'm located so maybe not something i should be getting into
This mod as described in this guy's thread won't be an issue with rain. Just drilling holes in the front airbox cover though WILL be an issue with rain. If you do exactly what was described in this thread then you'll be fine.
 

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Discussion Starter · #15 ·
Those of you who are worried about rain... No Worries bc the inlet tube sits far enough back from the vent holes.
Very nice acceleration through the rpm range from idle to redline. Intake noise is very subtle, an aftermarket foam filter would be a better option vs the oem paper.
 

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Discussion Starter · #16 ·
Some other ?'s/answers regarding this topic on another forum, thought I would share here in case it comes up later...

Air Fuel ? regarding this mod w/without a full system: Not to aggressive of an airflow mod, your bike will still run in the stoich air fuel range Honda runs all of there street worthy bikes off the show room floor.

Stoichiometric air-fuel ratio
: air-fuel ratio at which exactly all the available oxygen is used to burn the fuel completely or atleast to the best possible value.

Generally you'll see your factory off the floor bike running an AFR of 14:1-15:1, yes that's pretty lean and mostly bc to meet federal emissions standards even sound pollution in some cases. On the other hand... We have performance to gain from this through tuning


After this mod and a full system, I would recommend some type of fuel controller. Doing some research now with the new PCV(power commander)which will allow a wide range of tuning options. Just a few are fuel/timing maps, rpm control, launch control, quick shifter and even more... More info to come soon.

You'll be fine with this mod and a full system AFR wise, your ECM will compensate enough. For tuning purposes I would recommend a fuel controller with both mods together to extract maximum power with correct AFR's, should tune for 13:1 across the board. Yosh full system by itself bolt and go gives you 1hp over stock.

? regarding direction of inlet tube (stock location vs rotating) and the option of drilling/cutting holes vs not:

Drilling holes is not true ram air but does allow cool air to enter the intake rather than pulling heat/hot air from top of motor. Cool air equals more power


I did notice improved acceleration from idle to redline and def more up top.

Hope this helps answer some ?'s, good luck and happy modding!
 

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Just wanted to give a big thanks to Joyridn for posting this up. I had several people asking me to do this on mine and make a video/thread about it but with so many requests lately I just hadn't got to this one yet. Very appreciate you got to this first so that all of our forum members have quick access to a wonderful free mod.

:motorcyclesmilieK:
 

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I ripped mine out

That was pretty easy since I already had my panels out.



Some other ?'s/answers regarding this topic on another forum, thought I would share here in case it comes up later...

Air Fuel ? regarding this mod w/without a full system: Not to aggressive of an airflow mod, your bike will still run in the stoich air fuel range Honda runs all of there street worthy bikes off the show room floor.

Stoichiometric air-fuel ratio: air-fuel ratio at which exactly all the available oxygen is used to burn the fuel completely or atleast to the best possible value.

Generally you'll see your factory off the floor bike running an AFR of 14:1-15:1, yes that's pretty lean and mostly bc to meet federal emissions standards even sound pollution in some cases. On the other hand... We have performance to gain from this through tuning


After this mod and a full system, I would recommend some type of fuel controller. Doing some research now with the new PCV(power commander)which will allow a wide range of tuning options. Just a few are fuel/timing maps, rpm control, launch control, quick shifter and even more... More info to come soon.

You'll be fine with this mod and a full system AFR wise, your ECM will compensate enough. For tuning purposes I would recommend a fuel controller with both mods together to extract maximum power with correct AFR's, should tune for 13:1 across the board. Yosh full system by itself bolt and go gives you 1hp over stock.

? regarding direction of inlet tube (stock location vs rotating) and the option of drilling/cutting holes vs not:

Drilling holes is not true ram air but does allow cool air to enter the intake rather than pulling heat/hot air from top of motor. Cool air equals more power


I did notice improved acceleration from idle to redline and def more up top.

Hope this helps answer some ?'s, good luck and happy modding!
 

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Just wanted to give a big thanks to Joyridn for posting this up. I had several people asking me to do this on mine and make a video/thread about it but with so many requests lately I just hadn't got to this one yet. Very appreciate you got to this first so that all of our forum members have quick access to a wonderful free mod.

:motorcyclesmilieK:
Yea you're the only one getting super indepth vids..... Come on
 
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