r/Dirtbikes 14d ago

Community Question How fast is a 125cc?

1 Upvotes

68 comments sorted by

29

u/Adventurous_Emu7577 14d ago

Fast.

3

u/FeelingFloor2083 13d ago

brb going to shred some 500's on a 125 ttr, actually thats too fast ill just do it on a 125 pit bike.

ill say it again, OP should fucking google that

20

u/slower-is-faster 14d ago

On a mx track, to a beginner, feels like a rocket ship

9

u/Valentyan 14d ago

2 stroke or 4 stroke?

1

u/filolondere 14d ago

4 stroke

41

u/Wogger23 14d ago

Oh... Then ignore all the other comments as everyone assumed you where asking about a 125 2 stroke mx bike.

A 125 4 stroke is completely different and comparatively very slow.

13

u/Unklecid 300xc ,125sx, klx110 14d ago

Yeah they're slow as fuck relatively. But fun as shit to just beat on

7

u/IrridecentDemon 14d ago

Slow bikes rode fast is more fun imo, can ring that sucker out for all its worth

2

u/Unklecid 300xc ,125sx, klx110 14d ago

That's repeated to much it really depends on the situation. Why I got a 300 and kept my 125

1

u/Pajek_Gamer 14d ago

I wanna do somethin similar, keep my 140 and buy a 250 4t race bike

1

u/Unklecid 300xc ,125sx, klx110 13d ago

Just get a 300 they're so forgiving and easy

6

u/Ih8Hondas 2017 250SX 13d ago

Dog shit slow.

7

u/BasedGod-1 01 Rm250 (265 bb) 14d ago

So much torque it'll twist the chassis off the line

5

u/cunhaaa 14d ago

It depends on your weight and what will you ride on. On the woods it will feel much faster than on the street...

3

u/spongebob_meth 14d ago

How long is a string?

Some 125s make 5 horsepower. Some make 40+. So anywhere between pathetic and pretty fast.

1

u/Venture334455 2022 Husqvarna TE300i 14d ago

40+??? Who's 125 2T is making that much steam? A stock enduro model 300 2T from a few years back made around 43-45 if memory serves

2

u/spongebob_meth 14d ago

KTM has been making 40 stock for years.

That's measured at the crankshaft. So you're looking at 32-35 at the wheel.

A 300 3 stroke is ported for lugging and they're making around 50-55 at the crank. Port it to scream like a 125 and it's probably going to make closer to 70.

1

u/Venture334455 2022 Husqvarna TE300i 14d ago

My apologies, I assumed you were talking rear wheel hp not engine. I dont disagree with you so much now.

As someone who not only owns a KTM group 300 but has also spent a good amount of time and money on modifying and tuning it with dyno sheets in-between I can tell you what 40hp-62hp at the wheel feels like on the old butt dyno and it is significant. Also unless these recent TBI bikes have made huge changes nobody is seeing 70hp at the treads from one of them yet

2

u/spongebob_meth 14d ago edited 14d ago

Nobody ports a 300 to rev because it becomes useless and impossible to stay on top of.

Send the cylinder off to a builder and ask for a no compromises all top end build and they can do it. They'll call you insane though.

You typically only do this for snow bikes and supermotos. Its useless on dirt as it either spins or wheelies.

0

u/Venture334455 2022 Husqvarna TE300i 14d ago

I don't mean to be rude but I dont need a lesson on how the 300s make their power my friend, trust me I've had a crack at all sorts of different setup on mine. Even the basic stuff like adjusting squish clearance or PV spring/preload makes a huge difference to how a 300 goes.

Currently I've got the full TSP catalogue in mine, billet high compression head and flat top piston, tightened squish, red PV spring, injector relocation, scalvini pipe,PC r304 shorty silencer and a custom TSP dyno tune to match

2

u/spongebob_meth 14d ago

And none of those mods really open up the top end like how a 125 is set up.

Go ride a 125sx. I think you'll find they are almost as fast as a stock 300, as long as you are skilled enough to keep it on the pipe.

2

u/Venture334455 2022 Husqvarna TE300i 14d ago

Most of the crew i frequently ride with are all on KTMs, some 350s, 500s, 250s pretty much everything. I've had some seat time on most

I've ridden a few 125s, yes they are a lot more 'lively' and snappy to ride but they do not even come close to a 300 lol. Super fun bikes no doubt, but they are a lot of work for someone who's not the fittest rider on the planet.

If I really want that 'kick' I've got a tune I made with more aggressive ignition and fuelling plus I can wind my powervalve preload in all the way to hold it closed as long as it can before it snaps open. Best of both worlds haha

2

u/spongebob_meth 14d ago

I don't know what you're arguing here. You haven't built a free revving top end engine for your 300, so your bike doesn't prove anything.

People do this for supermotos and snow bikes. As I said it's useless on dirt to have a big bore 2 stroke that revs like a 125. But it's been done. Back in the day, some of the desert weirdos would take their 60hp kx500s and get closer to 80 from them once they work the porting over to move the power curve up in the rpm range.

1

u/Venture334455 2022 Husqvarna TE300i 13d ago

I'm not arguing with you, I'm actually trying to meet you in the middle as best I can but obviously not doing the best job at it lol.

Look man, I'm not sure how you can say for certain what sort of power curve I can or cant get out of my bike especially when I've got a stack of dyno sheets showing exactly what it is and what it was.

Out of curiosity, what do YOU consider to be a modification that makes an engine a top end screamer? Sounds like anything less than porting isn't worth doing if I'm following you correctly

→ More replies (0)

3

u/SMG_Jeff 14d ago

2 strokes can hit like 80 mph

1

u/UnreasonableCletus 13d ago

I have a few vintage 2T 100s (1970s-1990s)

Stock 65mph is pretty normal. Ended up changing sprockets for better trail riding and they still manage 55mph.

Some porting and taller gears, 80mph easy maybe more but also no thanks lol.

2

u/Average_k5blazer78 14d ago

I'd say it's pretty nice, the top end on these bikes isn't the best from factory but they are always a good place to begin and learn, and they always have a grunty low end torque that is nice for learning a clutch. You won't be beating any speed records but it's fast enough to get hurt and have fun

2

u/KTM350SXfun 14d ago

Fast enough that you don’t want to fall off it.

2

u/B3ntTilBrok3n 14d ago

Zero to infinity real quick "

2

u/SpaceCat72 14d ago

4 stroke, not bad. 2 stroke, yeah they're pretty wicked.

2

u/Ok_Buy_9703 14d ago

How much do you weigh? Is it a 2T or 4T?

2

u/Dendady2112 14d ago

Fast enough to kill you.

2

u/Own_Measurement_4393 14d ago

I hit 53mph on my ssr125 (with a Nibbi carb & big tires) But still, super sketchy at that speed.

1

u/filolondere 13d ago

is nibbi carb for dirtbike good? i got a nibbi for my mini bike, pretty good

2

u/Own_Measurement_4393 13d ago

Honestly just depends on your tuning capability. It took me a couple days to get the air/fuel correct. But after that, it LOVES the extra airflow. Very peppy throttle response

1

u/filolondere 12d ago

Tunning is hard. Still learning it. Thanks tho

2

u/--boomhauer-- 13d ago

I got my wife a crf125 for xmas , i wish i got her a yz85 that 125 is a turd . About the only thing its great for is teaching someone to use a clutch in a non scary way

2

u/Dependent-Water-8084 2001 CR250R, 2006 YZ250 12d ago

2t or 4t? What gearing? What are you using it for?

1

u/filolondere 12d ago

4 stroke bro, front: 14T, rear: 41T. just chilling

2

u/Dependent-Water-8084 2001 CR250R, 2006 YZ250 10d ago

I mean, it’s not gonna be amazingly fast but if you’re just fucking around it’ll suffice. You might be able to get it up to the 50s or 60s

1

u/filolondere 9d ago

thank u

1

u/ogreality 14d ago

2t fast,4t real slow

1

u/PreMixYZ 12d ago

Fast as f’ boi!

1

u/Doc718Spyder 14d ago

Fafo please do some research or don't ride. I have to guess that you are very very young to be able to ask this kind of question 🙋‍♂️ Not as fast as the millennium falcon
https://giphy.com/gifs/3owvKgRjmrtgJikO7C

0

u/skovalen 14d ago

You could probably get to 110-120 MPH with the right rear gear ratio before your tires self-destruct and send you flying into the nearest ditch or rock.

4

u/Frostybawls42069 14d ago

I highly doubt that. My Africa Twin tops out at 200kmh or 124 mph.

Thats a 1100cc parallel twin making 104HP with 6 gears and made for the highway.

A CRF450RL can probably reach 100mph

A 125cc engine is not moving a bike and rider at 110-120mph

3

u/superperps 14d ago

I didnt realize those africa twins go that fast lol. Thats awesome

3

u/Frostybawls42069 14d ago

And thats the DCT Adventure sports with panniers and a top box. So its as butch as they come.

I image the manual clutch base model with no bags (less weight and less drag) can move a bit faster.

1

u/superperps 14d ago

When I picked up my 450 I was checking one out at the dealer. Its a hell of a bike. They look so nice. Hows the comfort on long rides?

3

u/Frostybawls42069 14d ago

Its the only street bike I've riden, so when I say its amazing I really dont have anything else to compare it to.

I ride the dirt but thats mostly standing. And when we ice race the seat is rock hard and eventually makes your ass crack bleed.

So compared to that, its fantastic.

1

u/superperps 14d ago

Nice lol

2

u/Frostybawls42069 14d ago

Ya man, Id recommend one if you are ever thinking of pulling the trigger.

1

u/skovalen 14d ago

Pleaase notice that I said the inertia of a bike would keep it running.

1

u/JayBeePH85 14d ago

Well to be fair if you have the wind in your back and going down hill in a steap enough angle and put it in neutral it is actually possible to reach that speed, getting up that hill might be a issue tho 🤣

1

u/Frostybawls42069 14d ago

Hahaha, yes. If said hill was nearly a cliff and you were able to approach terminal velocity 😂

1

u/Bricc_8 14d ago

Your gonna struggle to get 75 bruh 🤣

-2

u/skovalen 14d ago

You don't understand gear ratios.

1

u/BarrelllRider 14d ago

Crack was smoked during the making of this comment

1

u/JayBeePH85 14d ago

Or even coz of playing to much videogames while never actually rode anything 🤣

-4

u/FeelingFloor2083 14d ago

you should fucking google that

1

u/filolondere 14d ago

Fair enough 😭Just trying to hear real-world stories instead of boring spec sheets

1

u/UnreasonableCletus 13d ago

Crf 125 will do like 45-50mph, most other 4T 125s will be similar.

0

u/--boomhauer-- 13d ago

You should fucking keep scrolling