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Discussion Starter #1
The Grom guys have a top speed guru. Who is going to be the guy with the fastest Monkey? I think there’s a guy with a 170cc on here. My top speed on flat ground, no wind, no tuck, full face helmet, 225 lb ride is 60.5mph gps verified. Stock 125cc, 16t and 32t. Stock sprockets was 52 mph top speed. I drafted a semi at 69.5 with new sprockets, it felt stable. I have the yuminashi 1 to 1 fourth gear to install, but I think the 181 NEO will be able to power the stock 1 to .92 fourth gear. It felt real good drafting the semi, almost like third. I can only hope our troll buys a Monkey. One of our Grom heavy hitters bought one.

And we need Monkey stunters.
 

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Those monkey bike should be able to hit 80+mph with the right porting on the head, the right throttle body, the right F/I, the right ECU, the right gearing.

A 170-2v or 183-2v with the right porting and cam will EZ get you 70-80mph

Let the DIY and testing begin.
 

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Discussion Starter #3
Those monkey bike should be able to hit 80+mph with the right porting on the head, the right throttle body, the right F/I, the right ECU, the right gearing.

A 170-2v or 183-2v with the right porting and cam will EZ get you 70-80mph

Let the DIY and testing begin.
Thanks CiscoSanJose. I was looking back at your posts. I like your build style, fast but streetable. I saw a post from 2014 where you were determining how to install an O2 sensor. Thanks for laying the groundwork. I don’t necessarily want the fastest Monkey, I just want to keep up with cars. My Yamaha xt225 had 20hp, it did everything I need in the highway. So, I want a 24 hp Monkey. I’m going with a 181 Neo, port the 2v head, the injector that comes with the Neo kit and full Aracer RC1 setup.

So, which throttle body?

Any other fast Monkeys???
 

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a 170cc won't get you much in top speed even with changed gearing. The 170 kit will give you a lot of bottom end power, but top end is pretty much the same. I had a 170cc kit with a yoshimuira cam. Top speed was unchanged for the most part. It was just easier to fight a headwind.

I'm 250lbs. 125cc stock piston, Fueling, Yoshimuira cam, and full yoshi gets me right at 60mph verified GPS sitting bolt upright with no drafting or wind. top speed typically increases as it gets hotter outside with these bikes. So I'll revisit in the summer months.
 

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For reference, I'm 165lb and my basically stock Yellow without ABS with the full Yoshimura system, 14t front sprocket hit 61.7 mph in a tuck the other day, verified using the iOS Speedomter App at 5,053ft of altitude. My speedo showed 67mph.
 

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Discussion Starter #6
For reference, I'm 165lb and my basically stock Yellow without ABS with the full Yoshimura system, 14t front sprocket hit 61.7 mph in a tuck the other day, verified using the iOS Speedomter App at 5,053ft of altitude. My speedo showed 67mph.
ok, now we are getting some baseline. Awesome. I am cornfused. Is 14f stock? I think I changed to 16f 32r for top speed. The Grom top speed guys like 16 32. I think.
 

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Discussion Starter #8
For reference, I'm 165lb and my basically stock Yellow without ABS with the full Yoshimura system, 14t front sprocket hit 61.7 mph in a tuck the other day, verified using the iOS Speedomter App at 5,053ft of altitude. My speedo showed 67mph.
why change to a 14? I thought we wanted 16 32 for top speed.
 

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A monkey with a full exhaust, cam, and a fueling solution won’t pull top speed in top gear usually. You often have to shift down to third to make it up steeper hills and such. With the 14t front, you can stay in 4th.
 

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A monkey with a full exhaust, cam, and a fueling solution won’t pull top speed in top gear usually. You often have to shift down to third to make it up steeper hills and such. With the 14t front, you can stay in 4th.
Yep, and honestly I'm not going for top speed here. Our elevation where we live is a little over 5,000ft and I'm planning on riding my Monkey up to over 12,000ft so I need all the torque I can get up those mountain roads. The 14t has definitely helped out in acceleration and responsivness throughout the gears.
 

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Discussion Starter #11
Awesome info, thanks. I am at sea level in the Florida Keys. I plan to install a Neo 181 soon. Then fourth should have the power to push the 16 32. Should I keep the stock 1 to .92 fourth gear or go with 1 to 1? If the 181 can push it, the .92 should offer more top end. I drafted a semi and stock fourth was amazing, easy 69mph gps verified. It felt very responsive like third. So I think .92 might work with more displacement. There is no replacement for displacement!! I want the fastest Monkey in the USA.
 

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Just FYI, I've tried 17/32 and 16/32 on my NEO 181 and I finally settled on 15/32. 15/32 would get me to 84 or 86 mph dependent on the direction I was traveling. 16/32 or 17/32 was slower as the bike didn't have enough ass to push the tall gearing in 4th gear.
 

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Discussion Starter #13
Just FYI, I've tried 17/32 and 16/32 on my NEO 181 and I finally settled on 15/32. 15/32 would get me to 84 or 86 mph dependent on the direction I was traveling. 16/32 or 17/32 was slower as the bike didn't have enough ass to push the tall gearing in 4th gear.
I was waiting for you to chime in. I am following a few of you Grom speedsters and our one Grom guy that bought a Monkey. There’s only one guy missing. I’ve talked to him on the phone. Who could it be? Oh, and I pulled our troll out on my first thread. He went all in.

Anyway, thanks a million for the sprocket info. What do you think the yuminashi 1 to 1 fourth would do to the equation? It might let the 181 spool up.

I am laying out an eighth of a mile drag strip.
 

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It may help by closing the gap between 3 and 4th. I'm sure if I had a 5-speed the 16t would've been fine. The problem is the gap between 3 and 4 are so damn big you lose the rpm needed to keep pulling when shifting into 4th. 15t gave me enough pull to get out of the bottom of the gap and into the upper rpms to start pulling again.
 

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Discussion Starter #15
It may help by closing the gap between 3 and 4th. I'm sure if I had a 5-speed the 16t would've been fine. The problem is the gap between 3 and 4 are so damn big you lose the rpm needed to keep pulling when shifting into 4th. 15t gave me enough pull to get out of the bottom of the gap and into the upper rpms to start pulling again.
Very interesting, firsthand experience. I looked at the 5 speed. The final ratio is .92, same as stock. You are spot on, the only thing I saw was closer ratios bringing the rpm up to the .92. So...what should I do? Get the 5 speed? Use the yuminashi 1 to 1? The 1 to 1 might give me enough. I just want to terrorize Key West!!
 

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Discussion Starter #16
It may help by closing the gap between 3 and 4th. I'm sure if I had a 5-speed the 16t would've been fine. The problem is the gap between 3 and 4 are so damn big you lose the rpm needed to keep pulling when shifting into 4th. 15t gave me enough pull to get out of the bottom of the gap and into the upper rpms to start pulling again.
Very interesting, firsthand experience. I looked at the 5 speed. The final ratio is .92, same as stock. You are spot on, the only thing I saw was closer ratios bringing the rpm up to the .92. So...what should I do? Get the 5 speed? Use the yuminashi 1 to 1? The 1 to 1 might give me enough. I just want to terrorize Key West!!
Ok, I was wrong about the 5 speed final gear ratio. Not .92, but 1 to 1. So, I am definitely using the 1 to 1. What does it take to push the .92? Can anybody do it?
 

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Ok, I was wrong about the 5 speed final gear ratio. Not .92, but 1 to 1. So, I am definitely using the 1 to 1. What does it take to push the .92? Can anybody do it?
Grom Fatherz 210cc will pull it.
 

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5 speed vs stock gear ratios
the 1:1 is the Kitaco 5-speed, you will need to also order their speed sensor. If you do the Takegawa 5-speed you can keep your current sensor.
 
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