Where's my top end power?

[MB3]

Any reason you guys can think of why my bike runs cleanly and pulls strong in the first 3 gears, but when on the track, on the straightaways, it struggles once in 4th, 5th and 6th gears. What happens is that the according to the tach the bike hits about 10k, 10.5k rpms then wont pull to redline. I end up short shifting 4th and 5th just to get into 6th gear at about 9k rpm to maintain my drive. I understsand that chances are it wont hit redline in 6th, but should rip there in 4th and 5th gears. I am geared 15/43. My dad says to lose weight, thanks. Im 6'2" and 240lbs. My size is one of the reasons why I enjoy my big Kawi so much, it just fits right, and has incredible corner stability. The motor has 32k miles and has been compression tested across all 4 cylinders at 185lbs. The air filter is clean. Thanks in advance for any help.

[rybetz42]

Have u done any jetting yet?

[clarkmanning]

Fuel Pump?

[rybetz42]

Well if you have upgraded the jets in the carb, then the only other thing to do is change your sprockets. Some of them are designed mainly for acceleration, and some others are designed for top end, but you may loose some accel...

[Kawi_T]

No way is it the sprockets. If it couldn't pull 6th thats one thing, but it should pull 4th no problem. Sounds like a lean condition or fuel delivery problem. When you had the plugs out did they look really white? When lean they look really white, ideally they should look brownish but not necessarily black.

BTW, I went to Lehigh U and lived in Bethlehem for 4 years.
Tom

[MB3]

Thanks guys. Currently it has stock headpipes with a Yosh slip-on. The previous owner said it has an Ivans jet kit. I have a full Muzzy exhaust on another machine that I have been pulling parts off of. Unfortunately there is only 1 complete zx7r at any given time. Do you think the race exhaust would open up the top end? Or is it just more noise at the expense of smooth low and mid power delivery?

[rybetz42]

i deffinetely think an aftermarket exhaust will give some more top end power, not to mention if jetted right it will make your bike run richer. Most aftermarket exhausts effect all all ranges of power to your bike

[davewaibel]

I suspect you removed too much emissions stuff, and your actually running out of fuel- there is a pressure equalization circuit that allows the fuel to flow correctly into the carburator, if you removed all of the emissions stuff, you are suffering from this, you need the part that is on the front of the air box area, that keeps everything running right, other wize you will only attain about 80hp, before you begin to starve from lack of fuel.