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I think that's a key phrase right there. To accelerate heavier weight to those final 5 mph, takes considerably longer
Near top speed, it's everything to do with wind drag, and almost nothing to do with weight.

At 0 mph, it's all about weight, and nothing to do with wind drag (unless you've got a 45 mph head wind, lol.)

It's not that the lighter riders weigh less, it's that we can physically hide in the shadow of the fairings/windscreen better.
 

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Hit 97 drafting a bmw M4 going over 100. The rpm was almost at redline, this is stock gearing. As soon as I changed lanes my speed dropped back down to 92-93. Btw 90 mph is the speed of traffic flow on this freeway before anyone says its excessive, it's not. It's a normal passing pace :)
Were you in the tuck position?
 

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Last Weekend I tried to go as fast as possible, was the first time after first Service. It reached 150 kmh ( 93mph ) easily, the fastest recorded speed was 159 kmh (98,8mph).
Thats on a cbr300r full tuck, meaning chin on tank, measured with GPS on Autobahn with stock sprocket. I will try again soon with 15 sprocket.
 

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This is my bike that I did my record on, also since setting my record my bike has gone caput with fuel delivery issues and f'd up injector :/ a little secret on the bike's is the back pressure box (in two strokes this is a boost bottle mod) located under the tank by the injector. I will sell a mod box for it soon for 45$ to members of this forum and the cbr250r forum. As an alternative I will be posting a diy on modifying the oem box.
 

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Hey buddy.. I am right behind you..soon 60. ;)

Ummm..not in the same bed...lol
The good thing about being a Pensioner (Senior) as you guys call it.
Upside: You can get a free bus pass, no tax on government pension, or have to pay national insurance (health care), free prescriptions at chemists (pharmacy).
Downside: tax on private pensions, no holiday pay, can't take motorbike on the bus.
Def a no no re the bed, have the misses to keep me warm :)
 

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Specs 1858 miles Box Stock CB300F with Puig Naked Windscreen - 89 octane no alcohol

My 222lb and 88lb wifey - 1st runs - She like to go fast! (not the bike) hehe

Slight up hill - Up wind - 75 pegged for a mile

Slight down hill - tail wind - 87 (probably can work on that more)

Id like more power but I think its a good and safe starter bike, around town bike, have fun bike.

My brother (Serious crazy sport-bike rider) said "it can still kill ya"
 

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My CBR250-R would max out at 147-155kph. Fitted a straight through sports exhaust and K&N air filter.
Most I ever seen was 161kph going slightly downhill for about 6 kilometres.

Now have fitted the 305cc big bore kit. Bigger exhaust pipe, fuel controller, etc. On the dyno, power is now 35.4hp @ 9640rpm from 24.2hp @ 8500rpm. Went over 160kph with ease but now hit the limiter at 173kph.
Have a 15T gearbox sprocket that I will fit when I replace the 4 year old clutch (now screeching on initial take off).

Not for more speed is the sprocket getting fitted, more to alleviate the horrendous fuel consumption. Before getting 23.2Km/L which is around 65-66 mpg. Now it is 15Km/L, around 43 mpg. A horrifying 33% increase, that is near what my Isuzu pick-up does.

Can anyone advise me on how to modify the speedo to compensate for the 15T sprocket. Thanks.
 

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My CBR250-R would max out at 147-155kph. Fitted a straight through sports exhaust and K&N air filter.
Most I ever seen was 161kph going slightly downhill for about 6 kilometres.

Now have fitted the 305cc big bore kit. Bigger exhaust pipe, fuel controller, etc. On the dyno, power is now 35.4hp @ 9640rpm from 24.2hp @ 8500rpm. Went over 160kph with ease but now hit the limiter at 173kph.
Have a 15T gearbox sprocket that I will fit when I replace the 4 year old clutch (now screeching on initial take off).

Not for more speed is the sprocket getting fitted, more to alleviate the horrendous fuel consumption. Before getting 23.2Km/L which is around 65-66 mpg. Now it is 15Km/L, around 43 mpg. A horrifying 33% increase, that is near what my Isuzu pick-up does.

Can anyone advise me on how to modify the speedo to compensate for the 15T sprocket. Thanks.
The metric models in K/ph read 10% fast on the speedo - sorry to burst your bubble on the top speeds you claim. :D

By fitting a 15T front you reduce that error down to reading 3% fast, so it's a nice bonus.

I worked all this out using a GPS and the speeds shown to me on the electronic police 'your speed' signs back it up.
 

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The metric models in K/ph read 10% fast on the speedo - sorry to burst your bubble on the top speeds you claim. :D

By fitting a 15T front you reduce that error down to reading 3% fast, so it's a nice bonus.

I worked all this out using a GPS and the speeds shown to me on the electronic police 'your speed' signs back it up.
:eek: :crying:

Hi 'Kiwi rider"
I know by law, in the UK true speed must be lower than indicated. So aware that my readings would be higher than true. But having your bubble burst hurts :crying:
Thanks for the advise that my speedo will now only be +3% from true.
You can work out true speed using gearing, tyre diameter (distance covered 1 rotation) and rpm. Still have my old slide rule, remember them??

In 4 months will be 62 yr old.
Want see 200kph on my R3 after tweaking and will report what my CBR305R does at full belt

Ford in the UK had the most optimistic speedos fitted in their XR3 1.6i.
One neighbour said his could do 130mph, told him that was quicker than my 3.5 V8-S Rover. So challenge was on. He was flat out on my speedo at 108-110mph.
I pulled out, passed him and got home. He said I were doing over 140mph, replied that I never went over 115-118 mph and he never went over 110mph. His reply? My speedo was reading low.......
 

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... Can anyone advise me on how to modify the speedo to compensate for the 15T sprocket. Thanks.
As kiwi rider said, the 15T front sprocket will reduce the factory speedo error to about +3%, which most owners find acceptable, or close enough. That said, if you want to get your speedo readout spot on for any sprocket size or tire size changes, you'd accomplish that by using a unit called a Speedo DRD which is a small circuit board that plugs into the speed sensor wiring harness. It's very easy to install and program. The Speedo DRD sells for about $80 USD. I've been using one on my '12 CBR250R to correct for both the factory speedo error (+4%) and the error created by my 13T front sprocket (+7%).
 

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As kiwi rider said, the 15T front sprocket will reduce the factory speedo error to about +3%, which most owners find acceptable, or close enough. That said, if you want to get your speedo readout spot on for any sprocket size or tire size changes, you'd accomplish that by using a unit called a Speedo DRD which is a small circuit board that plugs into the speed sensor wiring harness. It's very easy to install and program. The Speedo DRD sells for about $80 USD. I've been using one on my '12 CBR250R to correct for both the factory speedo error (+4%) and the error created by my 13T front sprocket (+7%).
MotoMike,
Thank you for advise.
If it still reads +3% high then that is acceptable out here. The local police will shake you down if you have been speeding (Around $6.00) so I will leave as. When I get around to, will post my avg fuel consumption and top speed, albeit +3% high.

Go safe :angel:
 

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Remember too that, if your speedo is out by +3%, your odometer will be too. Bear this in mind if you want to be really accurate when calculating fuel consumption.
 
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Remember too that, if your speedo is out by +3%, your odometer will be too. Bear this in mind if you want to be really accurate when calculating fuel consumption.
Good point JNO. That odo inaccuracy can work in your favor tho. I'm about to advertise my bike for sale with 13% less K's on the clock than it's actually travelled. Sneaky eh.
Running that super tall gearing combo has paid off twice - improved fuel economy and a lower mileage on the clock. Gonna be dam hard sleeping straight in bed at night tho. :D
 
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