Race bike power loss - Kawasaki ZX-10R.net
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post #1 of 16 Old 06-28-2010, 09:57 PM Thread Starter
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Race bike power loss

I have a road race bike that I am having a mystery problem with. The bike normally has 160hp on my sponsors shop dyno. I was racing a national event this weekend and the bike dynoed 143hp

I can see in the graph that the bike looks to have a flat spot from 9500-12000 and it just levels out at aprox 140hp

I have swapped fuel pumps, dyno was the same.

I have done a leak down test and there is less than 1% loss per cylinder

I am hoping that someone may have some thoughts on where to begin.

ANY INFO WOULD BE APPRECIATED.

thanks guys

Justin
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post #2 of 16 Old 06-28-2010, 10:30 PM
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Dynos vary a lot, does it feel down on power on the track? What does the air/fuel look like during this late 'flat spot'?

Have you ever degreed the cams? Did you locktite the cam sprocket bolts? A slipped cam could cut power, especially if it is worse at high RPM.

Swap your spark plugs, coils, injectors.

1% leakdown is very little, a typical tight motor is more like 3-5%. Did you do the leakdown? Is it your gauge?

good luck,
Dean
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post #3 of 16 Old 06-28-2010, 10:40 PM Thread Starter
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I was unable to pull top gear fr more than a moment while accelerating down the straight during my last race. It is more than just the dyno #

While doing the leak down, at 100psi there was about 1 psi differential.

I have swapped plugs tonight, coils will be done as well. I do not have injectors though.
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post #4 of 16 Old 06-29-2010, 01:25 AM
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you could have a bum fuel injector, especially if you have been running race fuel in it for a long time. Do all of the spark plugs look like they are burning the same? i would also be suspicious of the cam sprocket slipping as mentioned before.
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post #5 of 16 Old 06-29-2010, 08:46 AM Thread Starter
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I will look at the cam sprocket tonight. I will have to see if I can get another set of injectors if the cam is ok.

Someone suggested to me the tps might be screwed. Is that a possibility?
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post #6 of 16 Old 06-30-2010, 12:57 AM Thread Starter
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Cam timing, leakdown, and valve clearances are all OK. New coils , fuel, and plugs added.

I will be doing a dyno pull tomorrow with the Power commander installed and if the problem persists, one with it removed.

Any other thoughts?
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post #7 of 16 Old 06-30-2010, 08:36 AM
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The TPS idea is good. You could try swapping out the throttle body assembly.
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post #8 of 16 Old 06-30-2010, 09:56 AM Thread Starter
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I will bring another TPS with me when I go to the dyno Room. I will have to see if the process of elimination works for me.
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post #9 of 16 Old 06-30-2010, 11:55 PM
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Do you still have your secondary butterflies in? I have seen where they won't open all the way. If they are still in take out the secondaries and see if that helps.

Green ones are faster

'05 ZX10
'05 ZX10 Race Bike
'92 KX 500
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post #10 of 16 Old 07-01-2010, 12:37 AM
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Do you loose power in all gears between 9500 and 12k? Might be worth checking each gear for a similar flat spot, even if you don't have baseline data for each gear. If it's a particular gear, I'd be thinking the trans has something wacked.

Trans slippage can cause power loss in autos, but I don't know M/C trans very well. Does it buck or surge during the flat spot, even slightly?

Just a WAG, but might the KIMS be kicking in from a false (not necessarily faulty, mind you - could be operating out of normal range, but still acceptable; don't know the parms and values involved) TP reading? Likely not, since KIMS doesn't operate at full throttle (assuming the throttle assembly can reach that point, as referenced in the ECU), however it's a thought IF you haven't already disabled it.

Since it's high in the rev range, vibration induced anomalies can occur, like the dreaded grounding problem. If you can monitor your voltage at those rpms, that might help (watch if it fluctuates). Your charging system and battery can also cause all kinds of strange behaviour, so ensuring they're up to snuff - terminals that are corroded and vibrate when loose may cause the injectors and fuel pump to loose some power, not to mention the coil packs.

I've done some work with autos and I've modified my own bikes, but I'm no pro. Just some things to think about. G/L.
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