hesitation around 4000 rpm
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hesitation around 4000 rpm
26 Jul 2011 15:55
I have a 77 KZ400 A with 17000 miles. I got it a couple of months ago. After having it for about 2 months, it has started hesitating a bit around 4000-4500 rpm with light throttle. If I give 'er a bit more throttle she takes off.
In the two months I've had it I've:
1. changed the spark plugs to B8ES from B7ES (original owner had these in)
2. started running premium gas, then switched back to regular as per advice on a forum
3. changed oil putting in motorcycle synthetic blend oil (previous owner put in blend car oil)
4. adjusted clutch and clutch cable as per manual specs
The previous owner told me he "rebuilt the carbs" just this spring though I'm not entirely sure what that entails (though he is a mechanic so I assume he knows what he's doing).
Any ideas on what it could be? Timing? Carbs need synced/adjusted? Need to run premium fuel with slightly cooler plug? Thanks.
In the two months I've had it I've:
1. changed the spark plugs to B8ES from B7ES (original owner had these in)
2. started running premium gas, then switched back to regular as per advice on a forum
3. changed oil putting in motorcycle synthetic blend oil (previous owner put in blend car oil)
4. adjusted clutch and clutch cable as per manual specs
The previous owner told me he "rebuilt the carbs" just this spring though I'm not entirely sure what that entails (though he is a mechanic so I assume he knows what he's doing).
Any ideas on what it could be? Timing? Carbs need synced/adjusted? Need to run premium fuel with slightly cooler plug? Thanks.
1977 Kawasaki KZ400 A with approx 17000 miles
Ann Arbor, MI
Ann Arbor, MI
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- MFolks
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Re: hesitation around 4000 rpm
26 Jul 2011 16:05
How's the compression? Air filter in good shape? Electronic ignition or points? Checked the valve clearances? No rust in the tank or float bowls?
1982 GPZ1100 B2
General Dynamics/Convair 1983-1993
GLCM BGM-109 Tomahawk, AGM-129A Advanced Cruise Missile (ACM)
General Dynamics/Convair 1983-1993
GLCM BGM-109 Tomahawk, AGM-129A Advanced Cruise Missile (ACM)
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- jmb275
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Re: hesitation around 4000 rpm
26 Jul 2011 16:18
All good questions.
Not sure about compression, need to buy a tool to do that I guess. Spark plugs looked good when I replaced them though (except for a bit of carbon fouling on the left cylinder) so I have no reason to suspect that.
Have NOT checked the air filter. That is probably a good place to start looking.
I'm guessing points on the ignition system. Not sure how I would know precisely (is this visible), but I'm guessing it's original. (I'm a bit of a noob here so sorry if I appear ignorant).
Have not checked valve clearances. Not sure how to even begin such an operation. Is this the place to start?
VERY little rust in the gas tank that I can see. Also I have a filter from the petcock to the carbs (perhaps this needs to be changed out). How does one get a fuel filter for this motorcycle?
Not sure if there's rust in the float bowls.
To be honest, I'm a bit "scared" of the carbs. I haven't ever messed with a carburetor and it appears from my perusing on MC forums that they are delicate little beasts.
Despite this confession, I'm not a complete dolt when it comes to this stuff. I work with airplanes, and do my own car repairs. I've just had no experience with a motorcycle, or with anything this old.
Any tips would be greatly appreciated. I'll report back on the air filter, etc.
Not sure about compression, need to buy a tool to do that I guess. Spark plugs looked good when I replaced them though (except for a bit of carbon fouling on the left cylinder) so I have no reason to suspect that.
Have NOT checked the air filter. That is probably a good place to start looking.
I'm guessing points on the ignition system. Not sure how I would know precisely (is this visible), but I'm guessing it's original. (I'm a bit of a noob here so sorry if I appear ignorant).
Have not checked valve clearances. Not sure how to even begin such an operation. Is this the place to start?
VERY little rust in the gas tank that I can see. Also I have a filter from the petcock to the carbs (perhaps this needs to be changed out). How does one get a fuel filter for this motorcycle?
Not sure if there's rust in the float bowls.
To be honest, I'm a bit "scared" of the carbs. I haven't ever messed with a carburetor and it appears from my perusing on MC forums that they are delicate little beasts.
Despite this confession, I'm not a complete dolt when it comes to this stuff. I work with airplanes, and do my own car repairs. I've just had no experience with a motorcycle, or with anything this old.
Any tips would be greatly appreciated. I'll report back on the air filter, etc.
1977 Kawasaki KZ400 A with approx 17000 miles
Ann Arbor, MI
Ann Arbor, MI
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- Patton
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Re: hesitation around 4000 rpm
26 Jul 2011 19:32 - 26 Jul 2011 19:52
[quote="jmb275" post=465069}...77 KZ400 A with 17000 miles...started hesitating a bit around 4000-4500 rpm with light throttle. If I give 'er a bit more throttle she takes off...Any ideas....[/quote]
Given decent compression, valve lash to specs, fat blue spark and proper ignition timing, would suspect imperfect carb pilot circuit.
Good Fortune!
Given decent compression, valve lash to specs, fat blue spark and proper ignition timing, would suspect imperfect carb pilot circuit.
Good Fortune!

1973 Z1
KZ900 LTD
KZ900 LTD
Last edit: 26 Jul 2011 19:52 by Patton.
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Re: hesitation around 4000 rpm
26 Jul 2011 19:46
Cleaning Motorcycle Electrics
Get some of the De-Oxit electrical contact cleaner and figure on spending a good day going from the front of the bike to the back. It’s a plastic safe cleaner/preservative. www.deoxit.com is their website.
On the older Kawasaki's, a majority of electrical connectors are inside the headlight housing requiring removal of the headlight, then the fun begins.
Do one set of electrical connectors at a time to avoid mixing up what connects to where. Usually disconnecting, spraying with De-Oxit and reconnecting is about all you'll need.
However, when encountering the green crud of corrosion, a brass wire brush may be needed on the pins you can reach.
Some 400-600 grit wet and dry sandpaper strips rolled into a tube should reach the male and female pins in the more difficult to clean connectors.
Smoker’s pipe cleaners, cotton swabs and wooden toothpicks work as cleaning aids.
Really small electrical connectors may require the use of a welders tip cleaning tool assortment.
Most pins in the connectors are coated with a thin plating of tin, and others may be nothing more than copper or brass.
If moisture is added, the resulting corrosion lowers the voltage/current being carried causing dim lights, slow engine cranking, slow turn signal responce and lower input voltage to the ignition coils resulting in weak spark.
The left and right handlebar switch pods will need attention too as they have circuit functions like turn, horn, run/stop, and start.
Usually a spritz or two with actuation of the switch is about all needed for these switches unless corrosion is detected and then careful disassembly is required.
The ignition switch may or may be not sealed to allow spraying the internal contacts. I urge caution if attempting to open this up as springs, and ball bearings may fly out never to be seen again!
If your bike has the older style glass tubed fuses, I suggest replacing them as vibration can cause internal failure. AGX is the type used, and most auto parts stores can get them for you.
Most bikes use 10,20, and sometimes 30 amp fuses.
Clean the fuse holder clips, looking for signs of overheating(discolored insulation, signs of melting).I use metal polish on a cotton swab, followed by spraying another clean swab with the De-Oxit and then rubbing the inside of the fuse clip.
All battery cables must be clean and tight for maximum current transfer. Check the cables going from the Negative(-) battery terminal/post to the engine mounting bolt
Also the one going from the Positive(+) terminal to the starter solenoid and from there to the starter motor.
If any battery cable feels ”Crunchy” when flexed, replace it, as possible corrosion is inside the insulation.
Each "Bullet Connector" will have to be sprayed to ensure good connectivity, especially the ones going to the energizing coil of the starter solenoid.
The alternator output “Bullet Connectors” are usually behind the engine sprocket cover and will need inspecting and cleaning too.
The turn signal light sockets will benefit from a spritz from the contact cleaner along with the tail light/brake light socket.
Some brake light switches can be sprayed on the actuating rod, with the spray running down inside to the electrical contacts, others may be sealed requiring replacement if the switch is intermittent in operation.
Some people put the Di-Electric Grease on cleaned terminations/connectors, I don’t, as I’ve read/heard it can cause problems when it gets hot, actually insulating the connections, so the choice is yours to use or not.
I think I've covered about all of the electrical systems on the bike.........
Why WD-40 Should Not Be Used On Motorcycle Electrical Items.
For many years, I was proponent of the use of WD-40 on fuse clips, fuses, switches and connectors. After hearing of other peoples experience with intermittent and sporadic activity, I shrugged it off as maybe they did something wrong in the application of the product.
It wasn’t until the time I rode my 1982 GPz1100 B2 model to downtown San Diego that I encountered the problems others had gone through.
After concluding my business downtown, I walked to where my bike was parked, turned the key to unlock the forks, and prepared to start the engine. The key was in the "On" position, yet I had no lights in the dash panel, the fuel pump was not running(I have FI), and the horn and tail light were not working.
Puzzled as to why nothing electrical was happening, I remember my earlier conversations about how WD-40 will over time become a non-conductor(more like an insulator). I had some pieces of 400 and 600 grit sandpaper in my tool kit and with them was able to scratch away the coating from the WD-40 on the fuses and clips.
After removing the insulating film, the bike started and ran like it should. Since that time, I’ve told people about the problem with WD-40. If you must use a contact cleaner, I recommend getting some "De-oxit" from Radio Shack Stores or any good electronic supply store.
Get some of the De-Oxit electrical contact cleaner and figure on spending a good day going from the front of the bike to the back. It’s a plastic safe cleaner/preservative. www.deoxit.com is their website.
On the older Kawasaki's, a majority of electrical connectors are inside the headlight housing requiring removal of the headlight, then the fun begins.
Do one set of electrical connectors at a time to avoid mixing up what connects to where. Usually disconnecting, spraying with De-Oxit and reconnecting is about all you'll need.
However, when encountering the green crud of corrosion, a brass wire brush may be needed on the pins you can reach.
Some 400-600 grit wet and dry sandpaper strips rolled into a tube should reach the male and female pins in the more difficult to clean connectors.
Smoker’s pipe cleaners, cotton swabs and wooden toothpicks work as cleaning aids.
Really small electrical connectors may require the use of a welders tip cleaning tool assortment.
Most pins in the connectors are coated with a thin plating of tin, and others may be nothing more than copper or brass.
If moisture is added, the resulting corrosion lowers the voltage/current being carried causing dim lights, slow engine cranking, slow turn signal responce and lower input voltage to the ignition coils resulting in weak spark.
The left and right handlebar switch pods will need attention too as they have circuit functions like turn, horn, run/stop, and start.
Usually a spritz or two with actuation of the switch is about all needed for these switches unless corrosion is detected and then careful disassembly is required.
The ignition switch may or may be not sealed to allow spraying the internal contacts. I urge caution if attempting to open this up as springs, and ball bearings may fly out never to be seen again!
If your bike has the older style glass tubed fuses, I suggest replacing them as vibration can cause internal failure. AGX is the type used, and most auto parts stores can get them for you.
Most bikes use 10,20, and sometimes 30 amp fuses.
Clean the fuse holder clips, looking for signs of overheating(discolored insulation, signs of melting).I use metal polish on a cotton swab, followed by spraying another clean swab with the De-Oxit and then rubbing the inside of the fuse clip.
All battery cables must be clean and tight for maximum current transfer. Check the cables going from the Negative(-) battery terminal/post to the engine mounting bolt
Also the one going from the Positive(+) terminal to the starter solenoid and from there to the starter motor.
If any battery cable feels ”Crunchy” when flexed, replace it, as possible corrosion is inside the insulation.
Each "Bullet Connector" will have to be sprayed to ensure good connectivity, especially the ones going to the energizing coil of the starter solenoid.
The alternator output “Bullet Connectors” are usually behind the engine sprocket cover and will need inspecting and cleaning too.
The turn signal light sockets will benefit from a spritz from the contact cleaner along with the tail light/brake light socket.
Some brake light switches can be sprayed on the actuating rod, with the spray running down inside to the electrical contacts, others may be sealed requiring replacement if the switch is intermittent in operation.
Some people put the Di-Electric Grease on cleaned terminations/connectors, I don’t, as I’ve read/heard it can cause problems when it gets hot, actually insulating the connections, so the choice is yours to use or not.
I think I've covered about all of the electrical systems on the bike.........
Why WD-40 Should Not Be Used On Motorcycle Electrical Items.
For many years, I was proponent of the use of WD-40 on fuse clips, fuses, switches and connectors. After hearing of other peoples experience with intermittent and sporadic activity, I shrugged it off as maybe they did something wrong in the application of the product.
It wasn’t until the time I rode my 1982 GPz1100 B2 model to downtown San Diego that I encountered the problems others had gone through.
After concluding my business downtown, I walked to where my bike was parked, turned the key to unlock the forks, and prepared to start the engine. The key was in the "On" position, yet I had no lights in the dash panel, the fuel pump was not running(I have FI), and the horn and tail light were not working.
Puzzled as to why nothing electrical was happening, I remember my earlier conversations about how WD-40 will over time become a non-conductor(more like an insulator). I had some pieces of 400 and 600 grit sandpaper in my tool kit and with them was able to scratch away the coating from the WD-40 on the fuses and clips.
After removing the insulating film, the bike started and ran like it should. Since that time, I’ve told people about the problem with WD-40. If you must use a contact cleaner, I recommend getting some "De-oxit" from Radio Shack Stores or any good electronic supply store.
1982 GPZ1100 B2
General Dynamics/Convair 1983-1993
GLCM BGM-109 Tomahawk, AGM-129A Advanced Cruise Missile (ACM)
General Dynamics/Convair 1983-1993
GLCM BGM-109 Tomahawk, AGM-129A Advanced Cruise Missile (ACM)
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- jmb275
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Re: hesitation around 4000 rpm
27 Jul 2011 08:58
Well, I worked a bit on the bike last night.
I don't have a compression test kit, but using the "hand at exhaust" method, it would appear that the left cylinder has a bit less compression than the right one. I also pulled the plug on the left cylinder (only has 200 miles on it) and it is pretty black. So it appears I am burning oil and have low compression.
Last night I changed out the fuel filter (which needed it pretty bad) and cleaned and re-oiled the air filter. I haven't yet checked valve clearances or timing.
I don't have a compression test kit, but using the "hand at exhaust" method, it would appear that the left cylinder has a bit less compression than the right one. I also pulled the plug on the left cylinder (only has 200 miles on it) and it is pretty black. So it appears I am burning oil and have low compression.
Last night I changed out the fuel filter (which needed it pretty bad) and cleaned and re-oiled the air filter. I haven't yet checked valve clearances or timing.
1977 Kawasaki KZ400 A with approx 17000 miles
Ann Arbor, MI
Ann Arbor, MI
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- TexasKZ
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Re: hesitation around 4000 rpm
27 Jul 2011 16:10
RE-oiled the air filter? What sort of filter is in there?
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
www.kzrider.com/11-projects/620336-anoth...uild-thread?start=24
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
www.kzrider.com/11-projects/620336-anoth...uild-thread?start=24
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- jmb275
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Re: hesitation around 4000 rpm
28 Jul 2011 13:08
Well, it's a foam filter. My understanding of foam filters was that they were coated in oil, and the oil is primarily what filters the air.
Am I wrong here?
Am I wrong here?
1977 Kawasaki KZ400 A with approx 17000 miles
Ann Arbor, MI
Ann Arbor, MI
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