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Engine become less powerful between 7k and 8k rpm

  #1  
Old 09-14-2011, 08:10 AM
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Question Engine become less powerful between 7k and 8k rpm

Hi there,

since I have bought this bikes few months ago, I notice that the power delivered by the engine in the bike varies a lot depending on the revs.
I understand that at low revs, engine will deliver less power since that's usual on 4-strokes engines.
From 9k rpm on the engine will deliver the maximum power.

BUT, I notice that between 7k and 8k the engine flattens a bit. Like a power loss.

It is a bit annoying, because 7k-8k is a usual cruising range of revs when going on non-urban roads.

Someone came across the same issue?

Thanks!

Thanks
Angel
 

Last edited by hebbo; 09-14-2011 at 08:16 AM.
  #2  
Old 09-14-2011, 05:38 PM
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Is that a stock exhaust? The power band is all about fuel delivery and
moving the maximum air through the engine. Think of a giant pump.
The exhaust (in part) controls how the air flows out of the engine.

Usually, following a change in exhaust system, the fuel-injection will need to be tweaked.
Yours might not have been. The F4i guys will be more authoritative in their comments.
I'm still a carberated guy (F3).

But, ideally you should be pulling through in a smooth
curve of HP. My bike starts to pull hard at 5-6k and by 7-8k and beyond, you better be definetly settled to the bike. My flat point is in the 4-5k+ -ish part of the band.

Being sane and on the street (not to mention gas milage), I seldom peek over the 12-14k band.

I'm not sure how you change the programing on a fuel-injected bike, but there is a way.
Other-wise, possibly run some Seafoam (or similar additive) to the fuel for a
couple of tanks, see if that clears out anything.

Ern
 
  #3  
Old 09-14-2011, 05:59 PM
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Hard to tell by the pic but it looks like a stock exhaust. And yeah, Ororo just finished her morning stretch and is ready to wake up around 7k RPM.

How much of the bike's history do you know? Did the previous owner install a PC or change the sprockets?
 
  #4  
Old 09-15-2011, 05:56 AM
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Thanks for your replies.
I know absolutely nothing about what has been done in te bike since I am the 6th owner! XD

The exhaust is the factory one, but looks like it was fit just before I got the bike from a dealer. I can notice this power loss since I got the bike, but really did not pay it too much attention. Now I am suffering it a bit more since I am more confident with the bike. (My first big bike)

At least, I wanted to know whether this is normal in these big 4-stroke bikes, or this model. My guesses were:
- Faulty spark plug not working properly at this range of revs
- Faulty injectors not working properly at this range of revs
- Faulty fuel pump?
- I would dismiss faulty exhaust although yeah, maybe the electronic commander is misconfigured.

Any thoughts?
Cheers
 
  #5  
Old 09-15-2011, 07:04 AM
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Look under the seat for something labelled Power Commander or something on the wireharness between it and through ecu. If a Po had another exhaust but left the pc in, it could be mapped wrong now.
 
  #6  
Old 09-15-2011, 07:12 AM
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I will have a look, but the only visible box under the seat was the alarm box, and I get rid of it few months ago. If it isnt just behind the rear light I dont think there is any PC.
Ill check anyway.
 
  #7  
Old 09-15-2011, 07:14 AM
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Just trying to eliminate the easy stuff before you go tearing into the fuel rails and such for no reason
 
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