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| warped one |
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warped one
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| plugger147 |
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plugger147
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 Posted: 02:16 - 02 Jan 2009  Post subject: |
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Thats the problem, you've changed your gear ratio's by wearing down your tyre so the speedo will be out. 
There could be loads of reasons why, needing a service/weather/binding brakes etc. Do you have any other symptoms?
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| Finglonga |
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Finglonga
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| Kickstart |
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Kickstart
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| Posted: 15:01 - 02 Jan 2009 Post subject: |
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Hi
If you are needing more revs in the same gear for the same speed then that suggests the clutch is slipping, or the tyre is seriously worn / low on pressure (very seriously low....). Clutch slipping could be the clutch plates, could just be badly adjusted, could be contaminated oil (ie, one of the oils that wet clutches do object to, or worse something like Slick 50).
Could also be the speedo is reading incorrectly (or was before and is now more accurate).
This is assuming you haven't put on new sprockets and changed the gearing.
All the best
Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing |
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| Pie-Roe |
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Pie-Roe
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| Posted: 16:30 - 02 Jan 2009 Post subject: |
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Is your chain loose? I swear I got told a loose can drain power.
Pyro
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| Al |
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Al
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| owdamer |
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owdamer
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| Kickstart |
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Kickstart
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| Posted: 17:22 - 02 Jan 2009 Post subject: |
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Hi
In any particular gear the revs and the speed speed are directly proportional. The only way for the revs to change at the same speed is if you use a different gear or something in the transmission is slipping (or a very slight change from tyre wear).
Basically doing 4500rpm rather than 4000rpm at the same speed in the same gear means that there is a mechanical problem.
All the best
Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing |
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| Pie-Roe |
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Pie-Roe
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| Posted: 23:04 - 03 Jan 2009 Post subject: |
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| Kickstart wrote: | Hi
In any particular gear the revs and the speed speed are directly proportional. The only way for the revs to change at the same speed is if you use a different gear or something in the transmission is slipping (or a very slight change from tyre wear).
Basically doing 4500rpm rather than 4000rpm at the same speed in the same gear means that there is a mechanical problem.
All the best
Keith |
I'm sure this is very simple but I still don't get it, but I'm really not physics or mechanically minded.
Surely if there is more resistance, like if you have a flat tyre or a loose chain, you lose power being put wheel to ground, and therefore you need higher revs per speed?
So for example with a correct tyre, if I'm doing 60mph in 3rd at 5k, if my tyre is worn, or my chain is loose wouldnt it cause the loss of power being transferred from the crank to being put down on the ground. So at 5k there'd be less power going to the ground and therfore you'd be going slower, but the engine would be working the same?
If I'm being completley retarded ignore me 
Pyro
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| Kickstart |
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Kickstart
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| Posted: 23:18 - 03 Jan 2009 Post subject: |
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| pyroforlife wrote: | Surely if there is more resistance, like if you have a flat tyre or a loose chain, you lose power being put wheel to ground, and therefore you need higher revs per speed? |
Err, think you are getting confused.
Yes at a constant speed if there is more resistance you need more thrust to overcome this. Normally you get that from using more throttle.
If you need more thrust than the engine can deliver at the revs that equate to the speed you are doing in the gear you are in then you change gear to one that is more appropriate, and then the revs change for the speed you are doing. Eg, 5000rpm in 5th gear might be 85mph, but 5000rpm in 4th gear might be 75mph.
It isn't the load that has changed the ratio of revs to road speed, but the change in the gearing that you are using. Those gear ratios on a normal gearbox cannot change themselves.
| pyroforlife wrote: | So for example with a correct tyre, if I'm doing 60mph in 3rd at 5k, if my tyre is worn, or my chain is loose wouldnt it cause the loss of power being transferred from the crank to being put down on the ground. So at 5k there'd be less power going to the ground and therfore you'd be going slower, but the engine would be working the same? |
To answer your last sentence, yes there would be less power and that would mean (assuming you are on full throttle) the car would not maintain the same speed and would slow down. But the engine revs would also slow down by the same ratio.
All the best
Keith
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| plugger147 |
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plugger147
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| Pie-Roe |
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Pie-Roe
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| Posted: 23:50 - 03 Jan 2009 Post subject: |
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| Kickstart wrote: |
Clever stuff
All the best
Keith |
I get it now, I knew gearing isn't dynamic but for some reason I was assuming it was changing along with the resistance and revs.
Pyro
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| Matthie |
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Matthie
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| Posted: 01:06 - 04 Jan 2009 Post subject: |
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One of the biggest factors I have noticed that changed speed/performance is tyre pressure, made a difference of 10mph on the top end of the FZ and a hell alot of stability. The tyres were dangerously low though, never presume the last owner had them at the right pressures. 
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