MNSBR: Super Grom Build - MNSBR

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Super Grom Build

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Posted 27 March 2018 - 09:01 AM

Over the winter I studded some Grom tires and rode on Lake Martha. Tons of fun!

Video from our old friend Momentum Photo



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Now I bought a 2nd Grom for a standard commuter and something to let family and friends ride who don't have a Grom/Scooter. I also want to use it as learner bike since I've spoken to so many people that want to learn to ride but don't have an opportunity to do so. (My primary Grom is built for stunting and not great for beginners.)

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The plan...
...is to build up my primary Grom to get some more HP and get it to cruise around a little more effectively. A stock Grom gets about 8.5hp to the wheel and if I go the route of a "Super 125" build, it will be about 15hp. The Super 125 kit keeps the 125cc cylinder and lower hardware, but adds a high compression piston, replaces the stock head with a ported/polished head, stiffer valve springs, larger throttle body/intake and a larger injector. A big bore kit (BBK) would be a bit cheaper, but the reliability on them doesn't seem to be quite as good.

I also have a new oil pump coming that will pickup oil from the back of the case during wheelies.

I have already built up the front suspension with an Ohlins kit and put a YSS shock in the rear. This alone was a complete transformation. With the engine build it should be a capable little scooter.

I also bought a new set of plastics (Full OEM set $126 :D ) This set is black. I might mix and match with the yellow, but I like the idea of going all black.

And I just picked up a 2nd set of OEM wheels to mount up my summer tires. Wheels are NOT as cheap as body work! This way the ice tires can stay right where they are on the original wheels.

The last piece I'll have to get before finishing the engine build is an aftermarket exhaust. I want to stay stock for keeping the volume down, but that would kill power on this build. Best exhaust option I can see now is the Yoshimura RS-2. It comes with a silencer plug.

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I haven't bought the Super 125 kit yet, but it will happen soon. The guy says he won't have stock in till the end of April.


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Posted 27 March 2018 - 10:07 AM

Cute Razor.

:popop:
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Posted 27 March 2018 - 10:13 AM

There's 4 big toys in the basement yet to come out of hibernation.
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#4 User is offline   crakerjac Icon

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Posted 27 March 2018 - 10:53 AM

Have you considered a ZS190 swap? It's a Chinese motor, but people seem to be going nuts over them. Apparently they bolt right up to the Grom (and Grom clone), put out about 15hp out of the box and have a 5 speed gearbox...
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Posted 27 March 2018 - 11:13 AM

Yes, but that's a carbureted motor, and still Chinese. I like the idea of a simple head/piston/injector upgrade to get 15+hp. I want it to last forever, if possible. The Super 125 kit will run on 91 pump gas and is claimed to make 16+ hp with the right computer setup. I'm going with a cheaper fuel programmer route and settling with the claimed 15+ hp. The cheaper programmer will have a richer fuel mix (less lean than other higher hp programmer options) that will help with cooler operating temps and longevity. People say they're still getting the usual ~100mpg with this. I'll be paying close attention to whether that's true.
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Posted 27 March 2018 - 12:13 PM

I'm not sure if this is needed, but does anyone have a 125cc hone? If I'm putting in a new piston and rings, I figure I better look into it. The Grom has over 4k miles.
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Posted 27 March 2018 - 01:38 PM

I'll be following this. I've been tooling around on my Z125 and I'm starting to understand why these bikes are so fun... but also frustrating.
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Posted 27 March 2018 - 02:02 PM

It will probably be early May when I make a real update. The Super 125 kit won't be shipping till late April.
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Posted 29 March 2018 - 03:28 PM

This super 125 kit sounds pretty sweet. 15hp would make these things stupid fun. What's that kit selling for? I went out and bought a diesel to replace my daily driver gas truck, so I'm seeing my self riding the grom everywhere and chance I can save the miles on the diesel truck.
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Posted 29 March 2018 - 03:45 PM

With the cheaper ECU option, it was $944 after shipping. Then I still need to buy an exhaust after that.

Kit: 749
ECU: 165
Shiping 30

Pipe: 450 if I get the Yoshi RS-2. That's a hard one to chew, but it's either that or a POS pipe that's way too fucking loud and still too expensive.
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Posted 29 March 2018 - 03:48 PM

That's not too terrible. What is are the ecu options? Just using a simple microsquirt setup or something?

Exhausts are stupid sounding and expensive for these damn things. That's for sure.
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Posted 29 March 2018 - 04:00 PM

It's all here: https://ren-mw.com/p...t/super-125-kit



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ARacer RC Mini Plus 2 ($400)
ARacer RC Mini Plus 2 Package ($725)
ARacer RC1 Super ($589)
ARacer RC1 Super Package ($1,189)
Finbro ECM ($165)



You can get a PCV or whatever else, I'm sure. But that's the list this guy offers on his website.


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#13 User is offline   Jim Hubert Icon

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Posted 02 April 2018 - 06:32 AM

View PostPOE, on 27 March 2018 - 09:01 AM, said:

And I just picked up a 2nd set of OEM wheels to mount up my summer tires. Wheels are NOT as cheap as body work! This way the ice tires can stay right where they are on the original wheels.

Luke, it's tempting to leave the ice tires mounted, but you really should dismount one side when you're done for the season. Moisture always finds its way inside and the wheels tend to rot from the inside out.

And say hi to "our old friend at Momentum Photo" for me.

EDIT: I just looked at the photos again. Can you run those dirt tires tubeless? If so, I'm thinking they may seal well enough that you could ignore what I wrote above (except the part about Jonah).

This post has been edited by Jim Hubert: 02 April 2018 - 06:56 AM

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Posted 02 April 2018 - 07:09 AM

Haha, yup, tubeless! I had to get the shortest screws they make (3/8") and they fit just perfect without poking through. For all of 8hp, I was hoping they wouldn't get ripped out. So far they look to be doing just fine.

I might just air down to try and minimize chance of moisture trapped in there. Good thinking.

I'm sure I'll run into Jonah soon enough. I'll pass along the message :thumbup:
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Posted 02 April 2018 - 09:26 AM

I once tried to break a bead by using a vacuum pump -- it did not work. But that would get all the air, and any moisture, out.
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