Top end increase

[chrisgsxr]

Hi every 1 ... Has any body any idea how to increase my cbr 600's top end speed?

Its good for 120 but sometimes thats just not enough lol

Any suggestions would be great

[alpine]

Only 120mph? I thought they could do more..

Would also help if you listed out any mods you have done so far?
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Current bike - FMX650.

[Dischord]

120MPH to be fair is pure shit, it must have been down geared or the engine is nackered. Check the sprockets and then go up a tooth on the front and down 3-4 on the back...or you could go up 2 on the front and down 6 on the back etc depends what you want.
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2012 KTM EXC 250

Check out my vids - https://www.youtube.com/user/KTMSparky/videos

[bish777]

aye that is low.

Is it revving out in top?

I'd think that a CBR600 should nudge 140+ even the earliest models.
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GSXR1100J

[lilredmachine]

Sounds like it's restricted? How old was the owner before you?
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Bikes: too many, too much for one man to maintain anyway.

[TUBZ69]

[G]

120mph seems a bit high for 33hp restricted, even if used to own a mito!

Unless it's quite downgeared, I reckon it's more likely it's just not running right.

If it was me, I'd clean out the carbs, clean the air filter and check the exhaust first.

Then maybe stick it on a dyno if it's still not doing great.

[Mr Nice Guy]

Couldnt it be a Jap import? Aren't the bikes limited to 112 like the cars?
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Suzuki GSX-R750K4 ~ Mivv GP

[Wafer_Thin_Ham]

[chrisgsxr]

I have no idea how to change the gearing of it maybe thats a job for the garage ?? .. its proper rapid all through the gears so no way is it restricted.

Maybe a dyno run is the answer ?

[chrisgsxr]

And it is deffo a UK bike not an import

[bish777]

you can change the gearing easily with a fairly basic toolkit.

A good start would be to buy a standard chain and sprocket set.
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GSXR1100J

[G]

At 120mph are you at the redline in top gear?
If you are, it's been seriously down geared.

It's not too hard a job to change sprockets yourself, but the front one can be a bit of hassle.

[mrlee1974]

Ive been 142mph on the early cbr600,that was 2up aswell so it does sound a little restricted.

[chrisgsxr]

Thing is .... and dont shout at me !!! it isnt at top revs at 120 lol its just that i dont think it wants to rev past like 7 when im at that sorta speed .. should it rev till red easily u think ?

[G]

First off, to do decent speeds, especially if the bike's getting a bit tired, you should be going up through each gear to redline, then changing up at the redline.

If you're not doing this, try doing this. Not sure on the gearing, but you'll probably get more power at 120mph in fifth than in sixth, so if there's more go in fifth that might get you to a higher rpm in sixth where it's got more power.

However, this sort of issue is usually more associated with peaky two strokes rather than older 600s.

[Fawbish]

If it wont rev past 7, I reckon its restricted mate. Resriction does not limit how fast you can go through the gears, rather what revs you can reach in each gear, like G said.

but if it wont rev past 7, 120mph with a 10% out speedo, could easily be restricted, my zx6 did just under 115 (probs about 110 true) and didnt rev past 9 when I had my restrictors in

Get it to a mechy mate, or to a garage, they can have a look for you. Try getting a mate though, cos garage will charge labour for looking
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"Oh....it looks like Average Joe's is forfeiting the match!" - "Yeah, its a risky strategy but lets see if it pays off for 'em Cotton."

[bladerunner]

If your doing 7K in top you aint riding it right. you should be in 4th at that rate. It's not a car and the 600's and 750's need revs to work properly. Try throttle to the stop and change up just before the red line.through the gears..See how fast it goes then. A lad down the road bought a vfr750 off me a couple of months ago and could only get 130 out of it..Until he learnt to give it some through the gears now he reports an indicated 150+

I've also just derestricted a honda hornet and with the restrictors in (Honda factory) it wouldn't pull more than 90mph at 8K rpm..so your revs vs speed sounds to be miles out!!! @17mph/1000 rpm

My blade is geared for 15mph/ 1000 rpm in top I dont think your cbr600 should be geared higher than a bike with 50%more cc

[Robby]

[Wafer_Thin_Ham]

[prawny1]

Find a nice long road and nail it in the higher gears you may be suprised at the pull in top at higher revs. sounds to me that you are just holding back on the throttle a bit if your getting 120 at 7000rpm you can easily drop a gear or two and then nail it to the red (but never over).
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hellkat wrote:

Some people are only alive cos its against the law to kill them.

[prawny1]

As far as restictors go most restrict airflow only, restricting your throttle would have the same effect, incidently is your throttle cabl e correctly adjustd and are you getting a full 90 degree rotation of your carb butterflies?
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hellkat wrote:

Some people are only alive cos its against the law to kill them.

[Pete.]

I don't agree with some of the comments above - the bike should make it to redline in top (supposing it's capable) no matter how early you change up the gears.
Once the revs have passed peak torque in top there should be no less reason for it to pull to the redline than if it had been thrashed to the limiter in every gear before. All that would change is the overall time it would take to accomplish it.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[G]

It may not have passed peak torque by 7000 rpm.

This is definitely an issue on smaller bikes like 125cc 2 strokes, especially unfaired ones.

However, I wouldn't expect of a 600 of that age in decent nick to have the same problem really.

[Pete.]

Well yeah but any bike that is accellerating should keep accellerating until drag overcomes power, no matter how low the revs when starting out. The example of small strokers is about the only time I could envisage where there could be two such occasions in one rev-range. No four-stroke would do it.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good