no power at high rpm

hello, im new to this site and i just picked up a 1982 kz750e. when the bike is in neutral with no load on it, it will rev to red line, but while driving it will only rev to 6 or 7 thousand rpms. it has no power on the highway and will only go 75mph. the carbs are clean, stock exuast, pod air filters and 135 main jets. any replies will be helpfull thanks.

Reving a bike to redline with no load is a very bad thing to do!

You have a carburetor problem. Your slides are not raising up the way they should. This is a common problem with CV carbs that have had pod filters put on them without modifying them to deal with the lowered vacuum. In many or most cases the carbs have to be rebuilt professionally to take the pods. Depending on who you give them to this may cost anywhere from $300-$600

Would also assure proper functioning of automatic advancer. Might be frozen in idle position, which allows reving up in neutral, but not under load.
With strobe-type timing light, should be able to watch timing move back and forth as rpm is varied by blipping throttle.
Good Luck!

he'd probably be getting alot of backfiring if the advancer was stuck in the idle position. Mine was stuck at the halfway point and she backfired like hell in the higher rpms.

If not already done, would also assure valve clearances being to specs and perform compression test.

Good Luck!

With 135 secondary main it should have lots of power. Assuming your carbs are Keihin CV34 like mine

Like patton says check the compression and the advancer and valve clearances.

I have to admit I have never heard of slides not rising being a common problem with CV carbs with pods Perhaps take off the carbs and check the slides and particularly the rubber diaphragms looking for holes or rips.

Finally, and this may be a dumb question........but are you sure it's firing on all cylinders. Fire it up, let it warm for a minute and spit or spray water on the exhaust pipes. Should sizzle right off.

JR wrote:

With 135 secondary main it should have lots of power. Assuming your carbs are Keihin CV34 like mine

Like patton says check the compression and the advancer and valve clearances.

I have to admit I have never heard of slides not rising being a common problem with CV carbs with pods Perhaps take off the carbs and check the slides and particularly the rubber diaphragms looking for holes or rips.

Finally, and this may be a dumb question........but are you sure it's firing on all cylinders. Fire it up, let it warm for a minute and spit or spray water on the exhaust pipes. Should sizzle right off.

I tuned up a suzuki GS850 that would not go over 30mph without the box on.

nads.com wrote:

JR wrote:

With 135 secondary main it should have lots of power. Assuming your carbs are Keihin CV34 like mine

Like patton says check the compression and the advancer and valve clearances.

I have to admit I have never heard of slides not rising being a common problem with CV carbs with pods Perhaps take off the carbs and check the slides and particularly the rubber diaphragms looking for holes or rips.

Finally, and this may be a dumb question........but are you sure it's firing on all cylinders. Fire it up, let it warm for a minute and spit or spray water on the exhaust pipes. Should sizzle right off.

I tuned up a suzuki GS850 that would not go over 30mph without the box on.

Kz440 slow to 7grand and no power without the box.