Make 125 go 5mphish faster

[Lalababa]

Hi everybodie ! Unfortunately I am not in a position to ride more than à 125 atm. I have ridden most of the older carbed 125s, in almost all road situations. I'd say most if operating well could hit the 60mph relatively handy esp. Varadero and shadow.And this speed is adequate enough for 60mph roads etc. However some 125s can only struggle to 60 and may become abit hazardous on a long busy stretch of 60+ road. Also if a headwind or hill.
I really like riding the gn125 but then again these can sometimes struggle to 60.
So it would be a great improvement to increase the top speed (by 5mph?) of these carbed 12hp ish bikes....ybr, cbf, gn,cm,el,gz,..etc.
Has anyone here managed to do this? And how did you do it? And how did it work out?
The more simple + cheap examples I've found on the net are: hiflow airfilter with larger main jet and needle raised,coupled with a hole drilled in exhaust.And/Or front sproket down one tooth.
I'm not interested in losing weight or going 150cc bore.
Also I'm thinking of getting a cm125 (probally post around 1990 ,as I think earlier ones were just over the 15bhp rule)
and I wondered if ye have any thoughts on these and what is their top speed?
Cordially yours,
Lalababa.
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Lalababa

[WD Forte]

Go on a diet if you is a fat boy.
Power to weigh ratio like innit?
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bikers smell of wee

[MarJay]

5mph is a huge percentage. You really would be better off just buying a bigger bike.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Lalababa]

I'm not fat just BIG BONED!
I can't get a bigger bike as I'm stuck on a 125.
I could just get a varadero or shadow (bit more expensive aswell)but I really like the gns or maybe à cm with straighter bars. I'll probally get a 12hp bike and do à bit of tinkering.
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Lalababa

[Lalababa]

Oh another mod I've heard would be to put a small windshield. What do ye think?
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Lalababa

[Ste]

[WD Forte]

As well as power to weight ratio there's wind resistance.
I've read that after a certain speed, most of the power from an engine is used just to overcome this.
Think about the mad speeds cyclists can achieve when riding close behind a pace car with a wind barrier.
Racers tuck down behind a fairing too, so they're not used just for looks are they?

As most 125s are regulated to a certain power output, getting an A2 licence at least would open up your options
and most of us seem to agree it's money better spent than going in the bigger piston 'moar powah' route.

Even if you were one of the few folk who could tune a 125 engine to the max without fucking it up
The frame, suspension, transmission and brakes were not designed or built to handle it so there could well be consequences.
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bikers smell of wee

[WD Forte]

OR
buy a scooty

My Deliveroo guy tells me his Forza and PCX 125s would do 70
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bikers smell of wee

[Lalababa]

That's it then! I've decided! After all the helpful advice a certain course of action has reared it's head in a most predetermined way!
1. Buy a 10hp marauder
2. Fit a small screen
3. Hiflow airfilter
4. Change jets up 2 steps, n needle down 1
5. Drill several holes in exhaust
6. Up 1 tooth front sproket
7. Polish ports
8. Get 150cc bore kit
9. Upgrade cam
10. Upgrade cdi
11. Use paraffin
12. Buy a shadow
13. Get a license
14. Buy a bigger bike
15. Lose weight
16. Sit back and enjoy.
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Lalababa

[MarJay]

There is a saying that applies to this and it starts like this “Ask a silly question…”
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[slowasyoulike]

If it has to be a 125 then the answer is surely to get yourself some lunatic old 2-stroke like the Cagiva Mito. You will be as fast as fuck then, at least for that magical 30 seconds before it explodes in a hail of piston shrapnel.

Or, y'know, pass your test and buy an old CB500. Or a Suzuki Burgman. Or pretty much anything really, if all you want is 65mph.

[Fullers1845]

My CB125F sits happily at 65 with a +1 front sprocket, will do 70 but that's right at start of red on rev counter.

I should add that I'm a weedy bag of bones though.
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Honda CB125F, Kawasaki ZX6R J1, 1978 Kawasaki KZ650, 1922 Sheffield-Henderson Blackburne grasstrack/sprint

[slowasyoulike]

[Fat Angry Scotsman]

[lisaansley]

I had a GN125 years ago, and honestly, 60 was about the limit. You can make them breathe a bit better with an air filter and exhaust, but don't expect miracles.

[Skudd]

[jeffyjeff]

In my lifetime of riding motorcycles, I have owned and ridden one 125, which I still ride regularly. My sample size is one, take it for what it is worth. I have noticed that as my YBR accumulates mileage, its performance at the top end is getting better. When my bike was new, I could usually achieve 95 kph, and occasionally coax 100 kph in a tuck if there was no headwind. Now it has 22000 km on the speedometer; I can hit 100 kph with ease, and coax 105 kph+ when conditions are right on my bone-stock motorcycle.

My advice to you, if an extra 5 mph is your worthy goal and regardless the bike that you eventually purchase, is to ride it hard. You know, like an Italian tune-up everywhere you go, every time you ride. Got a destination in mind? Choose the fast road and pin the throttle. You can coax your 125 to a higher level of performance without being abusive. Your bike is probably capable of giving you more than it is right now, it just needs to be pushed a little over an extended riding distance. As the miles increase, the engine will loosen up; internal friction and parasitic losses decrease, leaving you more at the rear wheel for increased velocity. I have observed this happening on my bike over time, and continual improvement hasn't topped out yet.
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History shows again and again how nature points out the folly of men - BOC