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Discussion Starter #1
hey all. was wondering if anyone might have a clue about why my cbr600f4 seems to top out around 120mph? no vibrations or anything that i can tell, just seems to run out of speed at full out...any thoughts?
 

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According to spec, you should be at 161 mph at 13.5K rpm - redline.
If your tire size is oem and so is your tooth count on the sprockets, then I don't know. Seems like you'd hear your engine not sounding right if you really are hitting 13K+ rpm's, and only going 120mph?

I'm an FI guy, so don't know that much about your particular bike. Plenty here do, they'll be along i bet...
 

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Discussion Starter #7
everything else seems fine to me, plenty of acceleration. just wondering where the top end went. had it to 140mph about a yr ago before i ran out of road but seemed to have a little more in the reserve at that point. now, she just feels a little heavy at 110-120mph.
 

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Discussion Starter #9
yea, jondog. like something is holding it back. i'm wondering if the carbs are out of sync. unfortunately i am just going to have to live w/ it for now.
 

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This doesn't make sense. Everything is stock. You're at redline. In sixth gear. Doing 120. Only explanation is that your tach and perhaps speedo are malfunctioning along with something wrong in your engine Holding you back. Sounds like an electronic issue.
 

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how the hell is 120 mph slow? where can you even test this besides an autobarn situation.

so about 200km/h isn't fast enough?

the old 900cc fireblade did 260 but struggled for anything more, the 954 i have doesn't like anywhere near 200, the fairings arn't stable and shake/wobble too much.

don't see why you'd care about top speed except a once off ego boost. unless your racing but they don't care about speed, its about lap times...
 

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sounds like a restriction personally, not that thats a bad thing, it means you going fast enough and time to slow down because if anything goes wrong, you may well die...

omg if my chain broke while i was riding and engulfed my leg, god damn i hope i'm not riding 200+ at the time! no leathers will save that...
 

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Discussion Starter #13
thanks guys. i appreciate the input. CT it's not an ego thing, it's knowing that my machine is running at peak performance...on the streets or the track (a 150mph straight away on a bike doing only 120 is definitely going to affect lap times by the way)
 

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peek performance can be tested in less than top gear/top speed no?

nah **** that, just do 200 on a bike you don't know, pray nothing goes wrong, sounds awesome!!!
 

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Discussion Starter #15
peek performance can be tested in less than top gear/top speed no?

nah **** that, just do 200 on a bike you don't know, pray nothing goes wrong, sounds awesome!!!
you don't know me, my bike, or the circumstances under which i ride. therefore, your commentary is neither appreciated nor asked for. feel free to get lost.
 

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Given that everything is OEM, sprockets, tyres, then the only variable in the transmission department is the clutch. Its the only component that is not 'locked' into place. Higher speeds are the place where a clutch will start slipping as the engine batlles against wind resistance and whole machine weight (rider, fuel, lugguage etc.).
Its where I would look first.
 

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Given that everything is OEM, sprockets, tyres, then the only variable in the transmission department is the clutch. Its the only component that is not 'locked' into place. Higher speeds are the place where a clutch will start slipping as the engine batlles against wind resistance and whole machine weight (rider, fuel, lugguage etc.).
Its where I would look first.
Bingo! I think we have a winner! If the clutch is slipping and you're tached out but only doing 120, it makes sense the clutch is slipping.

Good call jdugen!:thumb:
 

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my 954 had a problem like that. i took into the shop have had a full over haul done on it. after that everything was great. let us know what you find out
 

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Discussion Starter #20
jupiter - did they rebuild your clutch as part of the overhaul? do mind sharing what the cost for the work was?
 
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