power loss/bogging/hesitation in 4th and 5th gear

I recently purchased a 1982 kz650 H2 CSR. I am somewhat mechanically inclined but have limits. It has stock air box and newer air filter. The guy I bought it off of said that he had ultrasonically cleaned the carbs. It ran a bit rough before I had a chance to drain the old gas out but ran perfect when I put new gas in it. One day, after putting about 70 miles on the bike, I attempted to pass a car when I was in 4th gear. She could not get above 5000-6000 RPM and bogged if I gave it more throttle quickly. She has never been the same after that day. I then noticed that if I slowly rolled the throttle, it would eventually and slowly with some hesitation, get above 5-6000. It is even worse in 5th gear and is very difficult to get past 5000. The bike will start fine and will accelerate from 1st to 3rd fine and will redline in these gears if you let it. Even if it starts bogging in 4th and I downshift to 3rd, it will even have trouble in 3rd. Other symptoms to note:(1)- fuel light will come on and off even with tank full when this happens sometimes (2)-When clutch is pulled in while riding, the RPM’s will quickly drop and the bike will sometimes even stall. ….things I have tried…(1)-I have taken the gas tank, pet cock, new in-line fuel filter, and fuel line off and they are all clear/clean. (2)-I tried running the bike with the petcock on the PRIME setting thinking it was possibly a vacuum problem with the petcock but it runs the same this way.(3)- I also bought new carb intake boots(air box to carb) and secured them tightly and it still runs the same…the bike has electronic ignition(no points)

With a half tank (or less) of gas you may want to try cracking the fuel filler cap open a little and see if it still has the problem. It's possible the fuel cap vent is clogged a bit. Just be careful not to let fuel overflow. Ed

Ed, I ectually tried that today with no luck.

Do you have the service manual for the bike?
Have a look at the ignition Advancer, see if it is moving freely. Also with the New fuel lines/ filter, check the flow with the fuel line disconnected from the carbs, but going through everything else. Let it flow into a container, and see how long it takes to say fill a quart.
Drain the float bowls and see if any debris come out, water, rust etc.

Well according to my manual in 82 kawasaki went to BS32 carbs(cv's) on the 650's, (correct me if I'm wrong Ed). Sounds to me like the engine is starving for fuel in the upper gears. Just cause the carbs were cleaned in any fashion doesn't mean that debri didn't get in the fuel system after the fact.The idea that it ran rough when you got it indicates somethin in the system.I'm not sayin you should be , but if the previous owner had the carbs cleaned and then experienced issues like this , he may have gotten frustrated, given up and sold it. I would be willing to bet you got junk in the float bowls, or petcock and maybe in the jets. As part of the repair process I would buy an inline filter and place it in the fuel line between the tank and carbs.Before you tear the carb bowls off take the tank off and be sure the fuel flows freely from it, as the restriction maybe in the petcock. Hope this helps.

Godfrey

Those BS32 carbs will also have a screen at the fuel inlet, to the float valve, just above the needle and seat. These could be getting restricted.

I will look at the ignition advancer later this week and will update with my findings. Was reading about the advancer today in the service manual and didn't check it because I assumed it was fine seeing that the bike would get to the high RPMS in the first three gears. Also , I disconnected the fuel line from the carbs and drained the tank like this(without fuel filter attached) with the prime setting on the petcock. I will try this with the fuel filter attached later this week as well. Drained and cleaned one of the four bowls today and there was only a small bit of loose dark stuff at the bottom of it. I will do the remaining three. Thank you so much for your suggestions as I am learning as I go.
-dan

godfrey,
I beleive the bike was running rough because of the old gas that was in it because after I had drained the old gas out and replaced it with fresh stuff, it ran beautiful for about 70 miles before the problem started. Also there was a fuel filter (in line) on the bike when I got it but I replaced it with a new one when I noticed a small peice of rubber in it after the problem started. But like you said, the jets or bowls could be gunked up. I will update you when I have time to look at it next.
Thank you!

sounds like you probably have a handle on it, hope its a quick easy fix, best of luck

Motor Head wrote: ... look at the ignition Advancer, see if it is moving freely....

Good advice, imo.

danno8852 wrote: ... reading about the advancer today in the service manual and didn't check it because I assumed it was fine seeing that the bike would get to the high RPMS in the first three gears....

Assumption not necessarily correct, imo.

Would use timing light to determine whether the advancer quickly moves back and forth as rpm is varied by blipping the throttle.

At the very least, would lubricate the advancer pivot points (via access through the timing window).

The decrepit example shown below would likely seem to rev okay in neutral and might also get to the high RPMS in the first three gears.




Good Fortune!

.

First thing comes to mind is complete tune up including carb sync...

Do you happen to know if this bike was originally jetted for your elevation/climate conditions?

Condition (carbon, base ring, ground strap etc...) of the spark plugs may inform you quite a bit...