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Discussion Starter #1
Hey guys! I'm looking for some help with a bike my friend purchased(01 zx6r). I rode it back for him after the purchase and it struggled to go over 60 mph on the freeway. Although it did reach 70 mph a couple times before loss of acceleration(it felt like it just wanted to stall out) and it would return back to 60 mph(6000rpms in 6th). The bike would also jerk constantly. Another thing is I believe the exhaust did make a popping noise at times and there is a slight ticking sound. I have a decent amount of experience with tearing motorcycles apart, but not a Kawasaki and my friend is not mechanical what so ever so i'm trying to help him out.

The bike revs perfectly fine and sounds perfect in neutral. It pulls pretty good first through third gear although it does get sluggish and jerky at times. It idles fine at 1100 rpms. The first thing I did when we got it back was replace the spark plugs on it. That didn't do much of anything and is maybe slightly better. I was thinking the problem was electrical with the coils if not the plugs, but I have read on here it could be a million things from the chain to the clutch. Although, the clutch does seem fine and the transmission is very smooth. Also the bike only has about 13000 miles on it. Has anyone experienced something similar?
 

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Sounds like the common float-bowl equalization snorkel has been removed and/or the float-bowl modification performed by the PO wasn't successful.

Expose all the stuff on top of the engine and compare it to the parts micro-fiche to determine what's missing. You can also search ZXF using the embedded Google search bar to look for float-bowl snorkel, float-bowl mod, etc.
 

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Not sure but if it has ram air intake like mine does, it could be a vacuum line isn't connected properly. Check the vacuum lines and where they connect vs. where they are supposed to be.
 

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Discussion Starter #4
Thanks for the fast replies guys! However, if it were just a float/air intake problem wouldn't it only affect acceleration and bog the engine down? The bike is jerking constantly at times, especially in 6th gear. I didn't see anything abnormal with the carbs today when I was installing new plugs, but I didn't look closely. I used the search function to look for the float modification, but I couldn't find any step by step guides with pictures? Maybe I missed something.
 

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You'd be surprised how much a little pinch or improper setup of the intake system can make.
 

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Discussion Starter #6
So my buddy talked to the guy he bought it from today. Apparently the guy was putting unleaded fuel in the bike. I've never heard of anyone putting unleaded fuel in a motorcycle. I've always used the best gas available wherever i'd fill up. I'm not convinced that unleaded gas would create that jerking sensation, but maybe it caused damage over time? The unleaded fuel probably was the cause for the loss of acceleration as the pistons probably were not firing right.
 

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So my buddy talked to the guy he bought it from today. Apparently the guy was putting unleaded fuel in the bike. I've never heard of anyone putting unleaded fuel in a motorcycle...
What an idiot! You should only run motorcycle fuel in motorcycles. Send the bike back to the PO and thump him over the head.
 

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Alert!

:spam
 

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Maybe he meant he was putting regular unleaded in the bike, 87 octane instead of the required 91+ octane.


I would drain that tank and put fresh 91+ in it.


Low octane fuel in a high revving engine high compression engine is bad emm'kay, it might have been detonating at the higher RPMs if low octane fuel was used.
 

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Discussion Starter #11 (Edited)
Yes I meant 87 octane. I figured you guys would assume that considering almost every pump i've ever been to lists 87 octane as unleaded and 91 as premium. My fault for not clarifying.
My buddy talked to the guy and he said he said he had the bike out a week ago and had it well over 60 mph. But then he also replied by saying maybe it will run better with premium. So I'm assuming he had 87 octane in it. Which I never even thought of because I did not think people were actually that stupid. My buddy drained the tank today(after I told him it would be stupid to add octane booster to 87 octane fuel:crackup) and put premium in. He took it for a short ride due to rain and said the same problem still exists. I'll have time to look at it saturday, but it really could be anything so if anyone can point me in the right direction that would be great. I'm fairly certain it has nothing to do with the floats. I'll start with testing the electrical system unless someone else has better advice?
 

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Octane modifiers reduce pre-ignition almost exlusively at low RPMs when cylinder pressures and load are at their highest. As piston speed increases with RPM, the necessity for octane modifiers (i.e. high octane anti-knock index) is reduced. So depending on the engine (piston speed and engine loading) and many other factors, if the engine is run at 5K and above, the octane modifiers in 87 AKI would almost certainly be more than enough for ideal performance.

In other words, there's very little chance that fuel had anything to do with what you're experiencing. Doubt me? Fair enough. But when the bike still bucks and protests after you've run 91 AKI in it for several tanks, maybe then you'll start looking at the more likely source of 4K+ RPM bucking & protesting.
 

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Discussion Starter #14
It feels electrical to me. It could be air, but I know that when I put it back together last night all the hoses were open and the air intake for the filter was connected properly. I talked to a mechanic on the phone and I mentioned the carbs and fuel system and replacing something as simple as the filter. However, he said that the problem doesn't sound like it is fuel delivery as the fuel is already flipped over to the main jets at 6000 rpms. I've taken plenty of bikes apart and have put them together as well as installing dynojets into carbs. I know what i'm doing, but I only have one day to do it so I would rather skip the less likely scenarios. Carbs would be an all day project by themselves.
 

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... so if anyone can point me in the right direction that would be great. I'm fairly certain it has nothing to do with the floats...

I call TROLL a second time. Nobody could be this dense without it being intentional.

Sure it's funny, but come on!

Hey Ninja01, who said it was the floats? You're reading more into it than was said.

 

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It feels electrical to me. It could be air, but I know that when I put it back together last night all the hoses were open and the air intake for the filter was connected properly. I talked to a mechanic on the phone and I mentioned the carbs and fuel system and replacing something as simple as the filter. However, he said that the problem doesn't sound like it is fuel delivery as the fuel is already flipped over to the main jets at 6000 rpms. I've taken plenty of bikes apart and have put them together as well as installing dynojets into carbs. I know what i'm doing, but I only have one day to do it so I would rather skip the less likely scenarios. Carbs would be an all day project by themselves.
You may think you know what you're doing, but your arrogance will lead you astray. Unless you understand how and why a RAM air bike breaths like this...



...you are out of your league. Did you check the float bowl equalization plumbing yet? :crackup
 

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Discussion Starter #17
Someone mentioned above the float mod could be the problem. Although, after researching it and seeing the carbs that was not done. Also you seem to be breaking some laws of physics(although it has been awhile since I've taken physics while pursuing my B.S in engineering ). Check out the automotive math handbook if you don't believe me. Anyways I did google the problem and have found very few leads. This same question has been asked before on other motorcycle forums, but I haven't found a solution. I would not have made this topic if I had found the solution. But since no one here seems to have experienced this issue before I'll let the topic die and you can bother someone else with your ignorance.
 

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You offend so easily. Obviously you're not serious about finding a solution. The issue you mention is a well covered and a much discussed topic. Either the bike is starving for fuel because the atmospheric pressure inside the airbox is different from that inside the float bowl housing or there's some other vacuum issue or the bike's jetting has been modified in some why where it is outside the normal 13.0:1 - 14.7:1 AFR...in which case there could be a number of other compounding issues, one of which could include fouled spark plugs...or the engine isn't sound because it hasn't been properly maintained or has been abused. When was the last valve clearance checkup and what were the cylinder compression numbers?

But you already know about all that since you're an engineer and we're all dummies or just I am a dummy. One or the other or both.

And you best brush up on anti-knock index before you get into a verbal battle. Touting that someone has violated physics without any deductive proof certainly shows ignorance, but it's not on my behalf. Shall we continue down that road? I welcome your challenge.
 

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Just let him replace all the relays he can get his hands on in a day, because the carbs themselves would take him all day
 

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someone needs to tell him to post pics of the intake system. ALL of it. From the ram air tubes to the carbs, and everything in between.
 
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