CBR 900RR Mystery Sickness
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CBR 900RR Mystery Sickness
1st off this is my 1st post,so Im glad to be here,and hope I am posting this in the correct area.
OK,(this will be kinda long)I bought a 97 900rr bout 8weeks ago and noticed a bad "stutter" between takeoff and almost 4000 rpm,but only after it has been warmed up.Took it to the shop and the carbs were cleaned,plugs changed and the k&n filter cleaned.Still the problem persists.Next a stage 1 dynojet kit was put in,as I have the after market filter and exhaust on the bike.I would say that it improved it around 75%-80%.But the problem still there,up to around 2500 rpm,only after it is warmed up.Next it was put on a dyno,video taped and ran,and the video sent to dynojet techs who talked them through some stuff,but still nothing.Long story short,the shoppe eventually(after5weeks) said they could not fix the bike and suggested me take it to a dealer in charlotte,as the one here in hickory was not equipped to fix the bike either and was actually consulted as to the problem while in the shoppe.OK now heres my question:I have been talking extensively to a guy online,who is "tech"from kawasaki for the last few days and he is 100% convinced that it is,and I qoute,"A dye spot,or factory defect spot in one of the cylinders.Causing it to lose compression as it heats up and stutter".Is this even possible? if so would honda do anything as far as fixing the bike if this was a factory defect?Any other suggestions on what this might be???Thanks for listening to my ramblings and any advice is appreciated.I am trying to get the shoppe to upload the video on youtube so I can post a link to the video,if I do I will post that as well.
OK,(this will be kinda long)I bought a 97 900rr bout 8weeks ago and noticed a bad "stutter" between takeoff and almost 4000 rpm,but only after it has been warmed up.Took it to the shop and the carbs were cleaned,plugs changed and the k&n filter cleaned.Still the problem persists.Next a stage 1 dynojet kit was put in,as I have the after market filter and exhaust on the bike.I would say that it improved it around 75%-80%.But the problem still there,up to around 2500 rpm,only after it is warmed up.Next it was put on a dyno,video taped and ran,and the video sent to dynojet techs who talked them through some stuff,but still nothing.Long story short,the shoppe eventually(after5weeks) said they could not fix the bike and suggested me take it to a dealer in charlotte,as the one here in hickory was not equipped to fix the bike either and was actually consulted as to the problem while in the shoppe.OK now heres my question:I have been talking extensively to a guy online,who is "tech"from kawasaki for the last few days and he is 100% convinced that it is,and I qoute,"A dye spot,or factory defect spot in one of the cylinders.Causing it to lose compression as it heats up and stutter".Is this even possible? if so would honda do anything as far as fixing the bike if this was a factory defect?Any other suggestions on what this might be???Thanks for listening to my ramblings and any advice is appreciated.I am trying to get the shoppe to upload the video on youtube so I can post a link to the video,if I do I will post that as well.
Last edited by the cyclops; Mar 5, 2010 at 11:05 PM.
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From: Latvia
if dynojet stage 1 something improved than I think you are still wrong with jetting. and yes it could change when engine is warm, incoming air and fuel temp change. actually it is mess to get carbs jetted right.
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i have the dyno print out,and the "curve"is very smooth,a few techs have just kind of scratched there head when looking at dyno printout,then see what its doing.The video of my bike on the dyno was sent to dynojet and the techs there suggested a few things but to no avail.But I will def try the stock air filter.My next question is if it works,will the carbs have to be "dialed in"again with the new filter?
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From: Latvia
some other thoughts. has stock 900rr some heat shields between engine, filter box, carbs? maybe this is removed? than one ktm had problem fuel line was too close to engine and when engine warmed up bike started bogging because fuel start to bubble. but what about rpms near to red line? is engine there running clean?
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From: Northern Michigan
Also worth noting is to inspect the carb to engine boots. the rubber can become cracked over time and cause all sorts of issues. When the engine heats up, the cracks expand and let allow air to be sucked in creating a lean condition. This also applies to any gaskets on the engine. Check over the engine extremely close to see if any cracks are visible.
A good way to check is to get the bike up to running temp. Then get a spray bottle with water, and start spraying all around the carbs and just about everywhere on the engine. If you notice the engine bog down, thats a good indication that the engine has sucked in the water and your crack is somewhere close to that spot. Personally, I use wd40, but it has a flamability hazard, so go with extra caution and use it sparingly if you go that route. But it seems to work better than water for detecting leaks.
Its very difficult with a bike that has had a previous owner, or owners. Any number of things could have happened to it. It could have been overheated and have warped components, could have been torn down and not reassembled correctly. Could have a cavitating fuel pump, as shkapars said, could be fuel boiling in the line...
As far as your Kawasaki buddy. I'm not sure I would hold too much into that. thats a pretty specific diagnosis from a simple stutter. Plus, the die spot would have to go completely through the block, as the cylinders have sleaves in them. If its the piston hes reffering to, it would have more issues than just a stutter as dumping all that compresion into your crankcase would cause the oil to push into your air box and you would be seeing a significant amount of blue smoke.
A good way to check is to get the bike up to running temp. Then get a spray bottle with water, and start spraying all around the carbs and just about everywhere on the engine. If you notice the engine bog down, thats a good indication that the engine has sucked in the water and your crack is somewhere close to that spot. Personally, I use wd40, but it has a flamability hazard, so go with extra caution and use it sparingly if you go that route. But it seems to work better than water for detecting leaks.
Its very difficult with a bike that has had a previous owner, or owners. Any number of things could have happened to it. It could have been overheated and have warped components, could have been torn down and not reassembled correctly. Could have a cavitating fuel pump, as shkapars said, could be fuel boiling in the line...
As far as your Kawasaki buddy. I'm not sure I would hold too much into that. thats a pretty specific diagnosis from a simple stutter. Plus, the die spot would have to go completely through the block, as the cylinders have sleaves in them. If its the piston hes reffering to, it would have more issues than just a stutter as dumping all that compresion into your crankcase would cause the oil to push into your air box and you would be seeing a significant amount of blue smoke.
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Also worth noting is to inspect the carb to engine boots. the rubber can become cracked over time and cause all sorts of issues. When the engine heats up, the cracks expand and let allow air to be sucked in creating a lean condition. This also applies to any gaskets on the engine. Check over the engine extremely close to see if any cracks are visible.
A good way to check is to get the bike up to running temp. Then get a spray bottle with water, and start spraying all around the carbs and just about everywhere on the engine. If you notice the engine bog down, thats a good indication that the engine has sucked in the water and your crack is somewhere close to that spot. Personally, I use wd40, but it has a flamability hazard, so go with extra caution and use it sparingly if you go that route. But it seems to work better than water for detecting leaks.
Its very difficult with a bike that has had a previous owner, or owners. Any number of things could have happened to it. It could have been overheated and have warped components, could have been torn down and not reassembled correctly. Could have a cavitating fuel pump, as shkapars said, could be fuel boiling in the line...
As far as your Kawasaki buddy. I'm not sure I would hold too much into that. thats a pretty specific diagnosis from a simple stutter. Plus, the die spot would have to go completely through the block, as the cylinders have sleaves in them. If its the piston hes reffering to, it would have more issues than just a stutter as dumping all that compresion into your crankcase would cause the oil to push into your air box and you would be seeing a significant amount of blue smoke.
A good way to check is to get the bike up to running temp. Then get a spray bottle with water, and start spraying all around the carbs and just about everywhere on the engine. If you notice the engine bog down, thats a good indication that the engine has sucked in the water and your crack is somewhere close to that spot. Personally, I use wd40, but it has a flamability hazard, so go with extra caution and use it sparingly if you go that route. But it seems to work better than water for detecting leaks.
Its very difficult with a bike that has had a previous owner, or owners. Any number of things could have happened to it. It could have been overheated and have warped components, could have been torn down and not reassembled correctly. Could have a cavitating fuel pump, as shkapars said, could be fuel boiling in the line...
As far as your Kawasaki buddy. I'm not sure I would hold too much into that. thats a pretty specific diagnosis from a simple stutter. Plus, the die spot would have to go completely through the block, as the cylinders have sleaves in them. If its the piston hes reffering to, it would have more issues than just a stutter as dumping all that compresion into your crankcase would cause the oil to push into your air box and you would be seeing a significant amount of blue smoke.
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And now after being able to ride it on a 60 degree day for the 1st time,I have noticed that at idle(after about an hour of riding),the rpm's are fluctuating from right at 1200 for a 4-5 seconds,then dipping down to around 9 for a split sec then back up to 1200 again.It seems to be "stuttering"worse also as the day goes on...im just at a loss with this thing...