[Sergeant Pepper]

Hello everyone,

I'm wondering since the beginning how could we push that god dam 4th gear over 8k RPM ?

So far, with a full exhaust system + K&N filter i still can't push the 4th gear, it's stuck around 8k rpm + around 116 km/h in descent and around 106 km/h on flat road.

The gears 1,2,3 can easily reach the 9.2k RPM limit, but the 4th gear is definitely "heavy", where do you think that problem is coming from :

1) Injector / ECU limit
2) Mechanical limitation from the camshaft
3) Mechanical limitation from the cylinder / piston kit
4) 4th gear design

It's quite disappointing to have this 4th gear stuck, i'm quite sure that if it could reach the 9.2k RPM the top speed would be around 125-130 m/h

 

[StrayDog]

I think it just that 4th is just too tall for the power avalable.
Y ou need to either drop a tooth from the front sprocket,
or get more power ( 150cc upgrade)

 

[fashionrider712]

^^^^^ yes. with my 14t front i can hit the limiter on downhills with medium head wind. and on the flats with light head wind. but i also could hit the limiter stock in a full tuck downhill too.

 

[Sergeant Pepper]

Yah but i don't have any downhill long enough to push the limiter in Bangkok, the only ones are the bridges and they're not long enough to reach the limiter, anyway no bike should require a 2km downhill with no wind in order to reach a decent speed, its ridiculous !

 

[AJ Nin]

My Grom is stock and I have to watch myself or I get over redline. Exactly how high it would go, I don't know. I'm 136 lbs. and 5'6" which might be a factor. I think of 4th as an over-drive gear for cruising at wot so you don't stress the engine but I agree it is a little unusual for 4th gear speed to be under 3rd gear speed. This may be by design. What good is a redline if you ignore it though? I know they do this with race bikes, but they wind up doing a lot of engine work when they do that too. Redline is 64 mph on my bike and I have had it at 67 mph when I was tucked and not watching the tach. There are some other bikes like the Buddy with a 170i engine that doesn't go any faster than the Grom. Still, if I could safely get another 5 mph out of the bike, I would want that.

 

[CraftyCraft]

Depending on how much I food and water I consumed before the weigh in, the scale will read at 190-200 lbs. Not once have I bounced off the limiter in 4th without significant help.

IMO, pnp and better valve/spring combo. Bolt ons only go so far.

That being said, you can only go so far with what classifies as "bolt ons".

oh, and...

 

[BiG Chris]

Dont gear the whole thing down just change out the 4th gear to use the power you have

 

[fashionrider712]

Dont gear the whole thing down just change out the 4th gear to use the power you have

Where do u get the replacement 4th gear?


Sent from my BlackBerry 9900 using Tapatalk

 

[averian]

If you're going to crack the cases to install a 4th gear, maybe wait for a stroker crank to go along with?

 

[rkwfxd]

Yah but i don't have any downhill long enough to push the limiter in Bangkok, the only ones are the bridges and they're not long enough to reach the limiter, anyway no bike should require a 2km downhill with no wind in order to reach a decent speed, its ridiculous !

My Grom reaches a "decent speed" everytime I ride it. Is it decent for a 250-300? No, it is way too low. Is it decent for a 49cc scooter? Oh heck yeah it is way faster than any of those. Is is decent for a $3000 125cc economy Monkey bike? Yep - does just what I thought it would do.

 

[Sergeant Pepper]

My Grom reaches a "decent speed" everytime I ride it. Is it decent for a 250-300? No, it is way too low. Is it decent for a 49cc scooter? Oh heck yeah it is way faster than any of those. Is is decent for a $3000 125cc economy Monkey bike? Yep - does just what I thought it would do.

Well, i have to disagree.

The bike is way too slow, i'm not even talking about the price cause i bought it there and it costed me like 2.2K usd, but the bike is too slow and the 4th gear sucks this is not something that we can refute.

 

[ShapeShifter]

Well, i have to disagree.

The bike is way too slow, i'm not even talking about the price cause i bought it there and it costed me like 2.2K usd, but the bike is too slow and the 4th gear sucks this is not something that we can refute.

I disagree. For a 125cc horizontal it is right in the ballpark, in stock configuration that is.

More speed requres mods, either bolt on, glued on, welded on, cracked and stacked, or tapped.

 

[poolsgold]

The Grom is no way slow. I've owned 3 Yamaha tw 200's and non of them went over 70 without help. For a 125 the Grom is above average I would say.

 

[BiG Chris]

Where do u get the replacement 4th gear?


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Here you go YUMINASHI 25T FOURTH GEAR SPROCKET WITH CRANKCASE & CLUTCH CASE GASKET SET

 

[Sergeant Pepper]

Hi,

Will this change impact the speedometer ? If so, is there a way to reprogram it ?

 

[slevin]

The Grom is no way slow. I've owned 3 Yamaha tw 200's and non of them went over 70 without help. For a 125 the Grom is above average I would say.

I agree, I've owned only one tw200 and I feel that the grom 125 is more then average for sure.

 

[Gremlin]

I agree, I've owned only one tw200 and I feel that the grom 125 is more then average for sure.

^^yep!


Sent from my iPhone using HondaGrom.net mobile app

 

[Sergeant Pepper]

Yah but the tw200 is far away to be a reference in terms of speed.

Here in asia we got bunch of these small 4 stroke 125 cc of all kinds, for ex the msx's got more torque / power than the honda wave (honda innova) but no more top speed, the 20 years old 125cc honda sonic is faster, the new suzuki shogun is faster, all much cheaper.

 

[JimmyD]

The TW will beat a Grom in a straight line by a wide margin, though. The Grom might do 60 mph but it takes twice as long to get there.

My TeeDub pulls to 110 quite easy but it won't do much more than that. It takes a very LONG time to get it to 120. I changed the gearing to something taller than stock but I forget what.

 

[Nicksgrom]

Hello everyone,

I'm wondering since the beginning how could we push that god dam 4th gear over 8k RPM ?

So far, with a full exhaust system + K&N filter i still can't push the 4th gear, it's stuck around 8k rpm + around 116 km/h in descent and around 106 km/h on flat road.

The gears 1,2,3 can easily reach the 9.2k RPM limit, but the 4th gear is definitely "heavy", where do you think that problem is coming from :

1) Injector / ECU limit
2) Mechanical limitation from the camshaft
3) Mechanical limitation from the cylinder / piston kit
4) 4th gear design

It's quite disappointing to have this 4th gear stuck, i'm quite sure that if it could reach the 9.2k RPM the top speed would be around 125-130 m/h

Reset your ECU after 100 or so miles it bounces off that rev limiter in 4th I tested it down the motorway in (storm ciara) with strong winds tucked and was pulling 80mph with out a problem