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Discussion Starter #1
Anyone got a clue about this...

I have noticed recently that my engine response has been a bit odd.
It's a 1999 900 Supersport (FI engine) and she pulls beautifully and smoothly up to about 7500 rpm and then continues to make power after that but without the oomph and with a distinct 'fluttering' sound. The engine will rev all the way up to the rev limiter at 9500 but without much conviction.
It's hard to explain whether the 'fluttering' is a sound or a sensation - it seems like the gases are just escaping past the valves under load or something like that.

Does this ring any bells with anyone?

I'd love to be able to diagnose and fix this myself but I've no idea where to start.

Any input is greatly appreciated.

Thanks, Bill.
 
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Discussion Starter #2
Re: Can anyone recognise this engine problem? (Bill)

Clogged fuel filter
 
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Re: Can anyone recognise this engine problem? (section8superbike)

If your pipes have the emission testing holes on them, I'd check them to see if one of the bolts came loose.

I had that happen to my 999, had exactly the same issue which turned out to be a "massive exhaust leak".

Once new bolt was installed to plug the hole, bike started to run strong once again.
 
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Discussion Starter #4
Thanks guys.

I checked the emission testing bolts and they are both still in place and firmly tightened. So I went and got a new fuel filter and installed that.
Unfortunately the problem persists.

I'm now noticing that the revs between 7500 and 9000 are really lumpy and uneven. Not sure if it was always like that and maybe I just didn't notice.

I'm an idiot as far as this is concerned but my riding buddy said it could be a coil not giving enough spark at higher revs. Is it possible/probable that a coil may be at fault? This is a '99 EFI bike.

Any ideas? Please save me from having to to take my baby to the professionals..
 
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Discussion Starter #5
Re: (Bill)

Sounds like it may be a FI/ECU problem to me, but how many miles since the valves were last adjusted?
 
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Discussion Starter #6
Re: Can anyone recognise this engine problem? (Bill)

Bill,
I dont mean to change the subject, but you state your rev limiter is at 9500? Mine is at 8800rpm.


As far as the prob goes, do you have a PCIII on it?
 
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Discussion Starter #7
Re: (DesmoBob)

DesmoBob, I adjusted the valves just about 900 miles back.. everything seems nice and snug.

CaliDuc, I must apologise - I actually meant 9000 revs. DUH... Sorry about that.
No Power Commander - I bought my bike 25K miles back with 5K on the clock and it already had the DP Chip and slipons fitted... it has always revved up to 9000 where it hits the limiter...

This is perplexing.
 
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Discussion Starter #8
Re: (Bill)

Make sure the charging system is working correctly...
 
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Discussion Starter #9
I really do appreciate everyone's input here... although I'm starting to feel a bit out of my depth.

JHord, could this be affecting the engine in a certain rev range? Should I be looking to diagnose at rest or with the engine running (at high revs?)

Am I barking up the wrong tree with the ignition coil idea? Not that I can find them anyway... they certainly are not where Haynes suggested looking (pre '99 model admittedly).
Further idiotic question: do the FI bikes have the same coils as the carb models?

Yesterday I took her out on the freeway after I installed the new fuel filter and tested the engine behaviour at different revs. Slowly accelerating past 7500 induced a very lumpy uneven feel to the engine but it managed to get to 9000. I tried to maintain 7500 and was lurching unevenly along the road.

Today, quickly accelerating past 7500 there was no lumpiness but a slight fluttering sound like the valves clattering..





Modified by Bill at 5:24 PM 6/5/2005
 
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Discussion Starter #10
Re: (Bill)

Have you checked or replaced both plugs? Also I am thinking it is fuel related. Maybe a fuel pump going bad or maybe a clogged injector?
 
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Discussion Starter #11
Re: Can anyone recognise this engine problem? (Bill)

Did this problem just start out of the blue? Did you or anyone do any work on the bike recently? Did it come out of winter storage like this? How long has the problem been occurring? Have you checked all of your electrical connections to seen if they are firmed seated and corrosion free? Especially the injectors, tps sensor, etc?
 
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Discussion Starter #12
Re: Can anyone recognise this engine problem? (jager)

it is not common for a coil to fail. if it is ignition related, check the easily replaceable parts first the wires and caps, and the connection between the wires and the coils.
 
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Re: Can anyone recognise this engine problem? (cdansan)

Perform a compression test to evaluate the condition of the engine. Make sure the valves have been checked/adjusted prior to testing. Good luck
 
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Discussion Starter #14
Great input, thanks for the ideas. I work away from home a lot so only get the chance to work on the bike at weekends. I'll be checking some of these things out.
Caliduc, Cdansan, no I haven't even checked the plugs. Actually, I think they're due for replacement anyway - that would be a shocker if that was the problem. Hope it's not the fuel pump - do you know of a way to verify?
Jager, I had a lowside last year and had to replace the throttle control, slip-ons a nd a few other parts. I first noticed the problem after that. I've tried swapping the stock slipons and chip out for the DP items I have on now. The problem persists whichever setup I use. I am going to check over all the connections you mentioned this weekend - hopefully it is something simple like that.
Osofast, I'm going to have to do some research on that... I've never done a compression test before. Is that a big job?

Thanks for the ideas everyone.. I've got a lot to be getting on with now to try and fix this.
 
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Discussion Starter #15
Re: (Bill)

throw a set of plugs in it. might just fix it.
 
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