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Discussion Starter · #1 ·
I have a 1996 zx6r that was recently knocked over in a driveway. Broke the brake lever so it got left there for 2-3 days until I could install a new lever to ride it home - but on the ride home I noticed it had a hesitation around 5-7000RPM and leaked a bit of antifreeze in my driveway. I knew the spark plug wires were kinda ghetto before this so I removed them and replaced them.

Took the right fairing off and turns out the leak was because when the bike fell it partially crushed the main line on the right side of the radiator. I took a vice grip and some spare rubber tubing to avoid scratches and squeezed it back to being round and installed a new clamp, topped the radiator off and sealed it up. Those problems seem to be fixed, but on my test ride I let it warm up and then went WOT through the first 3 or 4 gears to see if it felt different. It ran like a champ, no hesitation and pulled hard.

All seemed well until I got to the stop light at the end of that road - the bike stuttered and died. It started up fine and stuttered really bad for a mile or so, then it seemed to clear up and it ran fine all the way home. I'm scared to run it WOT again until I figure the problem out - it doesnt seem like a vacuum leak and I don't think it's the carbs because it runs fine until after going WOT for a while.

Any ideas? I'm stumped.
 

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Try running it hard again, but it could just be something from the fall. Carb floats may have been tweaked, airbox might have come loose from the intake creating an air leak, or an air/vacuum hose might have been knocked loose.
 

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Discussion Starter · #3 ·
Well I took it on the highway (not hard, just riding a few exits down) and when I stopped it was running shitty again. I parked it and called a ride but I think I figured it out - when we refilled the radiator could there be a pocket of air by the water pump causing the coolant to not circulate well? It does circulate, I can see it when I take the radiator cap off and turn it over. That would cause it to heat up too fast while not showing the actual temp on the gauge because the temp sensor is in the back of the block where the temp might not be as high? I know its getting too hot, that seems like a pretty plausible cause?
 

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I would say that's not the problem at all.

It's something with your carbs. The tip probably jarred something loose.

Make sure all of the rubber hoses and such on the carbs are tight...and the boots that connect them to the air box and the engine itself.

Possibly a float got stuck that is allowing too much gas to leak in...but I doubt it would be the coolant at all.
 

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Discussion Starter · #5 ·
When I pulled it over the frame was almost too hot to touch but the temp reading on the gauge was only about half way up. If the carbs were just buggered up would the frame get so hot? I have had the bike since june and never noticed it getting this hot.

I don't know much about carbs, but how hard would it be to check the floats? Those are on the bottom of the carbs, which are really pointing back on this bike... would I have to take the carbs off or apart to check them?
 

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Does the bike light right up cold? Does the bike idle no problem? Does the throttle take the gas on a cold engine or say slightly warm so you can pull gas out of the main jet is WOT I am getting at. Then it is not the floats.

You may have caught a hot engine with a water leak? What color is the oil? Is it chocolate tan where that might be a head gasket leak with water mixed. So, did you say you added water and the frame was too hot to touch?

Remember, not a lean condition that it may overhead, but you said, "troubleshoot" and I say if it starts easy and takes fuel, then no float. If it runs like crap the cylinder is so lean you just have that engine die on it's face is way too much fuel is boil the fuel and not light it off almost.

So, top off the water. If you do not have a radiator pressure tester, then remove the cap; see if when the bike is running, you can see bubbles in the water? This is where compression is pushing out the gasket into the water jacket is one variable. The float is no need to touch if she is not over flowing at the vent tubes or say the over flow tubes.
 

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Discussion Starter · #7 ·
After my first ride today when it was running fine I took the radiator cap off and started the bike, coolant was moving through with no bubbles. I guess that rules out my orig. theory. That pretty much means its the carbs then.

Went back and got the bike in my truck - tried to start it but it didn't want to start this time and wouldn't run for shit. It would stay running with the choke on but if I gave it any gas it died. It's in the back of the truck for the night, i'm just going to take it to a shop. The guy who knocked it over is paying for it, I was just trying to save him a few bucks if it was something I could handle. I don't trust myself with carbs so to the shop it goes.
 

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Without going to alot of work I would remove the floar bowls/ drain screws & flush the carbs out 2-3 times. Chances are you got some crap in the carbs
 

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After my first ride today when it was running fine I took the radiator cap off and started the bike, coolant was moving through with no bubbles. I guess that rules out my orig. theory. That pretty much means its the carbs then.

Went back and got the bike in my truck - tried to start it but it didn't want to start this time and wouldn't run for shit. It would stay running with the choke on but if I gave it any gas it died. It's in the back of the truck for the night, i'm just going to take it to a shop. The guy who knocked it over is paying for it, I was just trying to save him a few bucks if it was something I could handle. I don't trust myself with carbs so to the shop it goes.
You may have a needle stuck closed, starving the engine of gas. Remember, when you twist the throttle, you are allowing more AIR in, not gas. The increased air picks up extra gas on its way to the combustion chamber.

To get at the carbs (assuming your bike is like my '93) , remove the seat, remove the gas tank (bolts at the front and rear of tank, plus fuel lines), remove airbox - now you can see the carbs. If you just want to check the needles, loosen each clamp on each carb where it hooks to the intake manifold, then pull the carb assembly off. You shouldn't need to remove any cables. Turn the assembly over (it will probably pee gas), then you can remove the float bowls.

Also, if it started this after a fall, make sure the throttle isn't boogered up somehow.
 

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Discussion Starter · #10 ·
Got the bike back from the shop yesterday, it runs a whole lot smoother now that the carbs have been sync'd and the hesitation is about gone- but it still runs like ass when it's hot. It runs fine after it warms up, but if I get on it or am sitting at a light for any amount of time (temp gauge reads fine, fan isn't on) it will run like complete crap (hesitation, feels like it's not running on all 4) for a few minutes until I get it moving (and it cools down I assume). It still seems like it's overheating... Any ideas?
 
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