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I have a 98 zx9r with 8000 miles. The bike hesitates for a second or two when I crack the throttle from a stop. The bike then accelerates normally. It does not hesitate during a roll on. I have new plugs, cleaned air filter, removed kleen air system, aftermarket can. Do the carbs need to be sync'd? Any help would be greatly appreciated.
 

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HESITATION

I think that looking at yor plugs may give you the answer...the intake and exhaust systems are like a see-saw..and have to be balanced. If you change the filter and exhaust (opening tehm up then you should have to change the carb settings or you will be running to rich. You may find that the plugs are running a little white-ish (or running lean), and you should change your carb settings to acomodate this. You could also try running a little cooler spark plug and see if this will help as you may be getting a little pre-ignition from running a little leaner than stock...With 8K miles you may also want to change your fuel filter (it's nice to have a spare anyway) and check the clamps to se that they are tight as welll as the airbox lid is properly seated. Let us know, for this FORUM is a tool that requires feedback for us to learn about problems from one another.
 

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Stammering

I think that we answered this somewhere else...Uncle Bob, did...IF you think that it is a vacuum leak...mix a little dish detergent in a spray bottle an dthouroughly spray everything down while the bike is ideling...should it all of a sudden pick up rpm's then spray the area again...it is most likely the area of hte vacuum leak...I think HOWEVER the answer will be found in adjusting your carbs. Because of your increased "breathing" your bike is probably runing a little leaner. adjusting the carbs a little richer should definately increase the performance of the bike and get rid of the misfire as you crack the throttle. Read a little bit on the forum and you will find hte same thing again with a backfire sound...
 

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Vacuum Leak

I had the same problem the other day. Mine was a vacuum leak. It only did it once in a while, and I took it all apart to find 3 of 4 vacuum lines had been removed along with the air box and the vapor evap recover system, and then the carbs were capped with loose fitting rubber caps (ala the prev owner :cry: ). The topper is that the vacuum switch was capped with electrical tape. So when I hit it, once in a while it'd hesitate, then go like normal... and occasionally I'd get a little popping backfire. Luckilly mine is pretty cut and dry in terms of trouble shooting.

So yah, try ljangell's method if you like. One that works for me is to remove the vacuum lines, plug one end, and hook the other to a bike pump. I then immerse them in water (a 5 gallon bucket is handy, or anything else you can easilly get the tube into and see) and gently pump the tube with air. This way the entire surface of the tube is being tested. You'll probably get immediate resistance so don't have an aneurysm pushing too hard... it won't take too much if there is a leak. If you see bubbles then you've found a problem... so much as it isn't coming from where you plugged the end. Hopefully you'll find the culprit, and if not you can reinstall making sure your ends are secure and airtight, and start 'er up. If it's still doing it, then you can move on to the carbs. Let us know what you find. Good luck.
 
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