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Discussion Starter #1
I have a super nice 85 ct70.. yes 85... it usually runs perfect... now it likes to just start going WOT on its own after warmed up... it starts on first kick, then i dialed in the idle so it idles fine, air screw is out like 2.5 turns. bike runs fine.... i go for a short ride and come back,,, put it in neutral. then all of a sudden it revs to wot.??? the throttle slide is not stuck,,, the throttle handle does back and forth with spring in it. all the carb and manifold parts and tight together with good seals/gaskets. carb is tight on air box looks good other then rubber boot a bit hard but dont think that should cause this... is it an air leak>?? and if so, why does it start fine until i ride a block then starts to rev high?? can it be anything other then air leak? stuck float? can throttle glide be stuck but handle still spring? its scary when wot and i have to kill it by turning off..
any ideas???
 

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Sounds like you have covered most of the likely culprits. Cold engines run richer, warm ones run leaner, that might explain some of it. You can test for air leaks using wd40, spraying the joints of the intake and looking for the throttle to die down as it temporarily seals the leak. The only other thing I can think of is that you are having fuel delivery problems. When carbs are running out of fuel, they will race. Try shutting off the fuel when this happens and check for fuel in the bowl.
 

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Discussion Starter #3
i have have this issue sine last summer when i covered up the bike for another year.. now same issue... my question is - if the throttle grip has spring in it when i turn the grip - does that mean its not stuck and ok?? or can the grip still have perfect spring in it and there be a problem? i may have lost a throttle slide part when taking it apart a bunch of times... like the w clip or c lip etc... but every time i take the slide out i put it back in perfect so it slides all way down..
it cant be a fuel problem as bike will run as long as i have rev controlled... as for air leaks - the bike runs fine until it warms up.. i go for a ride down the block come back - put in neutral and then it revs like mad and scares me to shut it off.... am i missing something here????
 

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Sounds like the slide spring is working, but it would be a good idea to check the slide parts. If the main jet needle c-clip or the W clip (retainer spring) are missing or installed incorrectly, the needle may be moving on its own. It will never work right without those parts.
 

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Discussion Starter #5
Here are all photos.. anything out of ordinary other than black plug? is there a gasket in the choke area?
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Looks like your slide and needle are correct. One possible explanation might be too much tightness on the throttle. If the inner cable is too tight, sometimes just turning the bars will make the throttle come on. There should be a slight lag between turning the throttle and the slide moving. I would also check float height and the valve for good sealing. It could just be dumping gas into the carb from an overflowing float bowl. With the richness your plug is showing, an air leak doesn't seem as likely.
 
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