Changing sprocket size - CG 125

[MisterPrice10...]

Evening all

I am considering putting the 900 into hibernation for the winter and getting myself a cheap commuter instead.

Ideally I would look at a cb500 or similar however a cg 125 is the winner at the moment as the missus can whack L plates on it.


My question is this:

Having always run standard sprockets on all of my bikes, would dropping the rear down a few teeth AND raising the front by a few make for a better top speed?

Having never done it I only have a basic understanding of how to change ratios etc.

Would this be too drastic of a change? Im not expecting a 150mph cg here, just one that will reach 70 comfortably without screaming the life out of it.


Thanks in advance!
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18 bikes later and still no idea what i'm doing.

[Riejufixing]

Initial feeling: leave it as it is, go "flat out" and change the oil more often.

Next feeling: If you're going to change the sprockets, add 1 to the gearbox sprocket (if that's possible) and keep the (new) rear the same, from an engineering point of view.

Another: It might achieve a slightly higher top speed, depending on whether there's any limit apart from power available.

Last: Buy something else that's a 125 but has a higher top speed as standard. Consider an RS3.


Edit: Wat is this about people wanting to tune CG125s? Just buy it and use it, just as it is. Maybe *still* change the oil more frequently, and oil other bits too as routine maintenance.

Re-edit: If Mr Honda wanted his CG125 to do 70 by having differently-sized sprockets, he would've made it like that.

[jaffa90]

"""" just one that will reach 70 comfortably without screaming the life out of it. """"
If you get one that does 65 comfortably let me know.

[WD Forte]

Do it!

Unleash the CGs power!
Get more miles to the gallon
A new head of hair
Lose pounds of unsightly fat
and save save save!

What could possibly go wrong?
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bikers smell of wee

[Teflon-Mike]

No.
Top speed is a function of power, not gearing.
Raise the gearing on a CG that much, it will likely just top-out at the exact same speed it does now... about 60-65 in favorable conditions.. just in 2nd or 3rd gear... and struggle to accelerate like you had pulled away in 2nd or 3rd gear!

On L-Plates.... you are limited to 15bhp. That allows about 70-75mph, again in favorable conditions. This is the preserve of the 'premium' 125's like the CBR125 or such, and even there not all will achieve them speeds that often, depending on their style. It's not in the perview of anything much that has air-cooling and just one cylinder, and certainly not anything with push-rods!

Learn to live with it... the low-power begging you work that much harder to get what little they may offer, CAN be 99% of the fun, meanwhile you can enjoy the ecconomy....
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[BusterGonads]

[BusterGonads]

[BusterGonads]

[MisterPrice10...]

Cheers everyone for their advice

It would seem that (not for the first time) my limited knowledge has led me astray! I had hoped changing the ratios might achieve the desired results but oh well!

I would rather ask on here first and learn something new than go out and buy one and be disappointed with the end result aha.

Might just convince the other half to do her full test, then can buy something with decent power I can commute on and she can have at the weekends!

Until the next silly question, cheers!
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18 bikes later and still no idea what i'm doing.

[bladerunner]

I'd still say gear it up a tooth on the front..maybe 2 if the engine is a good one that like to rev. Early jap CG's generally had a bigger carb and less restrictive exhaust and could rev untill the valve gear couldnt keep up...I dont know about the newer types but the CG is geared a little on the low side so you can carry a family of 5 up a mountain with no issues! worst case if you have reached top speed of 60-70mph in 4th then at least when you have a tail wind or down hill stretch then you can use 5th as your overdrive .....I regularly would hit an indicated 80-85mph down hill but still be the same speed up them. It's not like a CG has a narrow powerband or widely spaced gears anyhow. For the sake of £5 give it a shot.
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[Teflon-Mike]