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Discussion Starter · #1 ·
New to the grom world as of a couple months ago when I picked up an SF. Not a newbie to modifying minis, just new to a grom.

To start, this bike will be stunted and cruised down backroads. Not interested in gaining more top end or higher top speed but if it happens that's fine too. I'm looking to get the most bottom end power out of the stock bore. My main goal is to keep it reliable and dependable so BBK wasn't my first choice. Looking for advice from someone that has done the same. From a few searches I have started to gather these items:
Dingerbuilt Mid Length intake
Yoshi RS2
CJR Reflash
Kitaco Clutch Cover (I realize this takes weight off, but I see cartridge filter as a necessity)
Gearing changed to 15/40
60% Kitaco springs
Lifter Plate

Things I'm questionable if it will benefit the lower end:
Ported Stock Head
Yoshi ST-1M Cam
HC piston - not sure what brand

If anyone has any input, it would be greatly appreciated. If any of these takes away from lower end power than I am not interested and would appreciate the advice.
 

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I think your list looks great. I personally wouldn’t bother with the HC piston or ported head. We put a DHM HC piston in my buddy’s bike, it didn’t make much difference. I could see the ported head and HC piston combined doing more, but for what you want to do, I don’t think I would bother with it. The gearing you are wanting to run will probably make the biggest difference stunting.

The Yoshimura ST-1M cam is supposed to be great for low to mid power. I run the ST-2M cam because I wanted more top end.

Be sure you modify your oil pump, so you don’t starve the head for oil while doing wheelies.
 

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Takegawa or Kitaco Type 1 cam over the ST-1M. You could clean up the ports and maybe open up the exhaust a bit more, but anything more would shift power to the right.
 

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My opinion, you're not going to get more low end power from a Honda 124 cc single for stunting and cruising than the stock setup.
 

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Just stick with the gearing change. -1 countershaft and +2 rear gave my bone stock Grom more pop on acceleration and didn't cost any top end speed. Kinda makes me wonder why Honda didn't ship the bikes that way from the jump.
 

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Discussion Starter · #6 ·
I think your list looks great. I personally wouldn’t bother with the HC piston or ported head. We put a DHM HC piston in my buddy’s bike, it didn’t make much difference. I could see the ported head and HC piston combined doing more, but for what you want to do, I don’t think I would bother with it. The gearing you are wanting to run will probably make the biggest difference stunting.

The Yoshimura ST-1M cam is supposed to be great for low to mid power. I run the ST-2M cam because I wanted more top end.

Be sure you modify your oil pump, so you don’t starve the head for oil while doing wheelies.
Thanks for the input guys. I will ditch the idea of the HC piston for the moment. As for cams, it looks like from research that the best ones for low end power would be Takegawa S stage, and the Yoshimura ST-1M, unless there is one I am missing or overlooking. Of those two, which would give me the most low-mid range? If I do the cam I will likely put on the ported head as well.

And I already installed the Kitaco straight up oil pump just in case I went big bore further down the road.

Open to any and all ideas.
 

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takegawa, no head. That head will flow more air than you need low to mid range on a 125, therefore slowing down the velocity/ performance.
I agree with this 100%.
 

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Long tube header, long tube intake.

Exhaust that loops under the bike like Yamamoto or one that runs up under the tail.

Intake, Dingerbuilt has the long intake.
 
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