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Hesitation after 70mph or around 12-13k RPM
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Hesitation after 70mph or around 12-13k RPM - March 10, 2012, 05:41 PM

Hey All,

I just took my bike out of storage and went on a ride today. On my way home, I was overtaking someone and at about 70MPH , the bike started hesitating, and wouldnt go about 75. On the highway, I tried again, and with the throttle pinned open, the bike was not going above 78 and it was hesitating. I stopped at the local store and poured some ISO heat in the tank. When I stored the bike, I put fuel stabilizer in the tank, but when I went to ride today, I forgot to put the ISO heat in the tank before leaving. After putting the ISO heat in, I drove home about 35 miles, and it maybe helped a little bit with the hesitation, but it still does it, and it still wont let me go above 80. When i got home, i put it iin neutral, tried again, and the RPM would not go above 13k, even with the throttle wide open.

I changed my spark plugs before i put the bike in storage, they only have about 500-700 miels on them. Same with a new airfilter. THe battery has about 3k miles on it, but it started the bike right up, and ive kept it indoors and periodically charged it with a tender throughout winter.

Im thinking either the fuel injectors need to be cleaned, or bad plugs, or maybe some hose came lose but other than that IDK. Maybe i need to ride it a little bit longer for the ISO heat to work its magic on the fuel injectors? I rode about 200 miles today, if that makes a difference, so it should have pretty much new gas in it. Any ideas? Thanks!

Last edited by Riz; March 10, 2012 at 05:47 PM..
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March 10, 2012, 05:53 PM

Might have a dead cylinder. Start the bike up and squirt some water on each header pipe once they have warmed up a bit. If one is noticeably cooler (water doesn't evaporate/sizzle off quickly) then that's your dead cylinder. You can swap the injector with one from another cylinder to see if the issue follows it and then you'll know.

If they all seem to be getting good and hot then it could be the main line running to the injectors is partially plugged and not allowing enough fuel to flow.


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March 10, 2012, 05:56 PM

Have you checked the sparkplug wires and sparkplugs since you got back home? Maybe a plug wire came loose (or maybe you spit out a sparkplug, hopefully not, if you did you'd almost certainly notice the difference in sound)


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March 10, 2012, 06:25 PM

Quote:
Originally Posted by windblown View Post
Might have a dead cylinder. Start the bike up and squirt some water on each header pipe once they have warmed up a bit. If one is noticeably cooler (water doesn't evaporate/sizzle off quickly) then that's your dead cylinder. You can swap the injector with one from another cylinder to see if the issue follows it and then you'll know.

If they all seem to be getting good and hot then it could be the main line running to the injectors is partially plugged and not allowing enough fuel to flow.
Ill try the water thing first.

Quote:
Originally Posted by windblown View Post
Have you checked the sparkplug wires and sparkplugs since you got back home? Maybe a plug wire came loose (or maybe you spit out a sparkplug, hopefully not, if you did you'd almost certainly notice the difference in sound)
I was going to pull the tank off, but I probably wont be able to since im driving up to maryland tomorrow. So itll have to wait till I come back. Im thinking it maybe the main fuel line that may not be fully pllugged cuz when installing the battery, I didnt actually take the whole tank off, i just lifted it up from the back so it could have gotten loose in the process. Thanks!
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March 10, 2012, 08:02 PM

Also, what kind of sound would it be if the cylinder wasout. I thought it sounded funny when i was revving it in neutral, it wasnt as deep as it normally is, sorta high pitched. But at the same time, I never have rolled the throttle like that in neutral, so that could just be the normal sound
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March 10, 2012, 09:12 PM

I sprayed the headers, all four of them blew steam off the same.
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March 10, 2012, 09:14 PM

check the fuel line... could've gotten pinched/ kinked when you lifted up the tank.
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March 10, 2012, 09:20 PM

How is acceleration before you get to the higher RPMS? Could still be ignition or fuel I would guess.

Things that come to mind: Partially clogged or pinched main fuel line. Weak fuel pump. Ignition braking down at high RPM.

Or... Does your bike have a Exup Valve? Maybe it's sticking?


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March 10, 2012, 09:21 PM

Quote:
Originally Posted by drz1050 View Post
check the fuel line... could've gotten pinched/ kinked when you lifted up the tank.
You have quick mind and faster fingers grasshopper.


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March 10, 2012, 09:32 PM

Quote:
Originally Posted by drz1050 View Post
check the fuel line... could've gotten pinched/ kinked when you lifted up the tank.

Quote:
Originally Posted by windblown View Post
How is acceleration before you get to the higher RPMS? Could still be ignition or fuel I would guess.

Things that come to mind: Partially clogged or pinched main fuel line. Weak fuel pump. Ignition braking down at high RPM.

Or... Does your bike have a Exup Valve? Maybe it's sticking?
Im thinking itmaybe a kinked fuel line as well, but wouldnt the hesitation be present whenever I accelerate at any point, rather than just at the high RPM or 70+? 0-60, It doesnt seem to hesitate at all, and it seems powerful.

IDK what an exup valve is, but I have an 06 zx636.

When I sprayed the pipes with water, they all steamed off, but it seemed some dried up quicker than others. I guess the only way to figure this out is by taking off the tank! Ill try to do that in the AM
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March 10, 2012, 10:08 PM

Yup, you have an exup valve. It sits just behind the exhaust collector. If it's not opening it will restrict exhaust flow.

Under the tank is the area I would check first as 1050 pointed out. Higher rpms + a higher gear = more fuel flow required. A pinched line could be the culprit, and it fits with my motto: If a problem crops up start with the last thing you did.


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March 10, 2012, 10:08 PM

I would lean towards a vacuum leak. It would make sense that once you get to a certain speed you lose power. Because at that speed your bike is probably using whichever tube has a leak more than normal. I've seen cars that rode fine until they came to a stop (I know the opposite) but when they came to a stop they nearly stall out. The EGR tube that was hooked up was stable at speed but when the car stopped the slack was released and the vacuum leak happened.

*edit
also if you want to check for the more obvious vacuum leaks just listen to your bike idle. If you hear an odd hissing then you probably do have one but you may have to rev it up and listen.


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March 11, 2012, 01:33 AM

Thanks for the advice fellas! It was bothering me so much, I decided to open it up right now. The main fuel line looked kinked at the connection point to the tank, at the plastic end. I didnt turn it on yet since i didnt want to wake the neighbors revving the engine, but im pretty sure thats what it was. Im thinking about replacing that line now since it that plastic end looks really brittle now (you know how when plastic bends and u straighten it out again, it leaves that light mark on the plastic).
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March 11, 2012, 07:25 AM

Quote:
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If a problem crops up start with the last thing you did.
yep
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March 11, 2012, 07:57 AM

one posibility could be water in the tank. on 03-06 zx6rs water gets in to the tank some how. i would empty the gastank completly and put new gas in.


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