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Discussion Starter · #1 ·
Let me start off by saying that I have been around this forum for a little bit and have found volumes of helpful info. I completed the MSF course over the summer and bought my first bike, a 1990 Ninja 750R. It has a stage 3 jet kit and a vance and hines exhaust. Ok now on to my issue.

First off the bike has a tendency to vapor lock due to the gas cap not allowing the fumes to vent properly. So hopefully with the addition of a new gas cap that will resolve the issue. There other day I came to a complete stop at a signal in front of a marginally steep hill. As I began to go up the hill in first the bike started to bog down. I had the throttle wide open but it still continued to put along up the hill at about 1500 rpm. I realized I had to get home soon so I turned around and headed back down the hill. As soon I turned back down the hill the bike ran fine again without hesistation. What could be the problem? Is it time to clean out the carbs?

Also, my fuel gauge is horrifically inaccurate. When the guage reads half full it is really just about bone dry. Is there a float valve or something in the tank that i can replace to remedy this, because I have already ran out of gas three times within a month.

Sorry about the long post. Being my first bike and all I guess the winter months will give me a lot of time to get myself acquainted with this machine. Any help would be greatly appreciated.
 

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Discussion Starter · #3 ·
Well the guy I bought it off of said the owner of the bike before him was a mechanic who just tuned up the bike, but that definately sounds like a good place to start looking at things. Thanks for the advice.
 

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keep in mind that synching and tuning carbs isn't the same as cleaning. i'm trying to think of a problem that would become visible with pitch changes but i can't really think of anything. a mechanic might know more just from the symptoms..

i have the advantage of having many spare parts.. if i think my carbs are acting up i just throw on another set and see how they run! hehe.
 

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if the bike is stored outside or sees rain, there could be water in the fuel system.....maybe?....dirt in the carbs...possibly....but if the fuel is sloshing around half dry, then its missing the petcock and not getting delivered to the system.

does it act up with a full tank?

the float for the fuel guage could be removed and bent into position to show absolute empty...easy to do.

any other interesting quirks of this bike?
 

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Discussion Starter · #7 ·
Well the bike runs fine with a full tank, but when it gets to about half a tank it will stumble along every now and then. It's stored outside, but its got a water proof cover. I'm not sure how well it keeps out the condensation though. I've got the day off of work tomorrow so I will definately be spending some quality time with the bike and look over everything you guys suggested. Hopefully it will be something obvious, so I won't to have miss out on the next couple days of 60 degree weather.
 

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Discussion Starter · #8 ·
Originally posted by badassjake<br>if the bike is stored outside or sees rain, there could be water in the fuel system.....maybe?....dirt in the carbs...possibly....but if the fuel is sloshing around half dry, then its missing the petcock and not getting delivered to the system.

does it act up with a full tank?

the float for the fuel guage could be removed and bent into position to show absolute empty...easy to do.

any other interesting quirks of this bike?
I did some searhing on the boards, and found out that the 87-90 zx 750's weren't equipped with a petcock. I was thinking along the same lines as you when I ran out of gas for the first time.
 
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