Carburetor main jet fuel rate question

[Volksrod]

I know I should ask this in a Kawasaki Forum but trust your answers first.
2001 Kawasaki ZX6 with full aftermarket exhaust operating at 5200 feet altitude.
Bike runs well until about 6000 rpm and power flattens and feels like trailer hitching.
Fuel pump, tap, hoses and carbs have been cleaned both with solvent and compressed air and no longer appear to be cause of fault.
I also tried a "known good" ignition module with no improvement.
Cleaning and balancing the carbs did help but power is still low at higher rpms.
I couldn't verify from the customer if the carbs had been rejetted when exhaust was fitted.
I'm tempted to get out the wire gauge drill bits and open the mains a thousandth or two but would like input.
Thanks for helping with a non Ducati question.

[Bladecutter]

Sounds like a torn carb diaphragm.

BC.

I know I should ask this in a Kawasaki Forum but trust your answers first.
2001 Kawasaki ZX6 with full aftermarket exhaust operating at 5200 feet altitude.
Bike runs well until about 6000 rpm and power flattens and feels like trailer hitching.
Fuel pump, tap, hoses and carbs have been cleaned both with solvent and compressed air and no longer appear to be cause of fault.
I also tried a "known good" ignition module with no improvement.
Cleaning and balancing the carbs did help but power is still low at higher rpms.
I couldn't verify from the customer if the carbs had been rejetted when exhaust was fitted.
I'm tempted to get out the wire gauge drill bits and open the mains a thousandth or two but would like input.
Thanks for helping with a non Ducati question.

[Volksrod]

Thanks for the reply.
I did break down all four carbs, clean and inspect for damage like diaphragms and didn't find that to be the cause on this one.

[Oldfisti]

Sounds like you covered all the bases before having to re-jet. My friend had a similar issue with his Suzuki. Exhaust and stage 2 jetting ran ok.(not great)  He put pod filters on and it fell on its face. The stage 2 jetting was barely adequate for the exhaust. BTW, how do your plugs look?

[Volksrod]

I have opened up the main jets .002 and throttle response improved though loss of power still exists.
What role could throttle position sensor play in this?
It seems to sweep ok on the meter.

[Speeddog]

Perhaps a quickie dyno run to see what the mixture looks like.

Can you go back to the OEM exhaust?

[Volksrod]

I'm going to tape a fuel pressure gauge to the tank and go for a ride.
There are just as many Dynos in Albuquerque as there are Republicans.
I have no choice but to use my a$$-ometer.
Stock exhaust is long gone.
I'm getting frustrated and reading on the ZX forum this problem happens a lot and either never gets fixed or never followed up on..
I don't mean to sound flip, just not having a good time working on this one anymore.

[Volksrod]

It was the !@#@! air filter!!
Clean as could be on visual inspection, but when I rode it this afternoon with no air box the problem was gone.

[Oldfisti]

There's a kick in the pills! Glad you got it sorted. 

[Volksrod]

I don't really feel kicked on this one, and I have been kicked plenty so no ego to support.
The filter looked to be fine as is.
It's made of two layers of foam and after eight years of use and cleaning must have collapsed the cells, if that is how they work.
The bike had multiple problems that finally added up to lousy performance.
Thank you for the help.