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Discussion Starter · #1 ·
Hey guys, so i am dealing with a hanging throttle every time i apply any sort of throttle, it will hang at around 4-5k rpms for a good 3-5 seconds before coming back down and almost drowning out. I do not have a PC on it, and it has an ixil exhaust chopped down to a shorty GPing out the side. I dont know if the back pressure is whats screwing me up, but its also definately running rich, enough to sting eyes and after about 20 minutes idling it has fouled up plugs. there is a hint of white smoke coming out exhaust as well. I recently did a valve adjustment, and had to swap out half the shims on both ex. and in. valves, could the clearances from this adjustment cause it to change the mixture so drastically? Could it be something with the injectors? any help would be greatly appreciated, ive been banging my head against a wall for a week. Thank you
 

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7777
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Hanging throttle is often a vacuum leak or being extremely lean. How many of these changes did you do at once?
 

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Discussion Starter · #4 ·
07 zx6. and i did the shims and exhaust at the same time. is there a way to adjust mixture without a power commander?
 

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1993 Zx-7 L Model, 2006 ZX-10R
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07 zx6. and i did the shims and exhaust at the same time. is there a way to adjust mixture without a power commander?
Yes. ECU flash. Cheapest one I know of is Chris Moore of Moore Mafia in SC.

Otherwise, No.
 

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  • Adding exhaust without a tune makes a bike lean, more than it was stock, which was too lean.
  • White smoke says lean
  • I'll bet your plugs are snow white

I'm sure Chris is a great tuner, but he'd be guessing since your bike is not on his dyno. If you are going to play you have to pay, or put up with a poor running bike. Spend a few hundred and get it on a local dyno to fix this.

Is there any possible way to once and for all get rid of this back pressure myth? [/rant off]
 

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  • Adding exhaust without a tune makes a bike lean, more than it was stock, which was too lean.
  • White smoke says lean
  • I'll bet your plugs are snow white

I'm sure Chris is a great tuner, but he'd be guessing since your bike is not on his dyno. If you are going to play you have to pay, or put up with a poor running bike. Spend a few hundred and get it on a local dyno to fix this.

Is there any possible way to once and for all get rid of this back pressure myth? [/rant off]
I plan on sending my ECU to him after taxes. He has templates for all sorts bikes with different combinations of mods. Though, I do agree that it's better to have your bike dyno'd and tuned. If only all engines could wear and perform the same.
 

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80,81 GS750L, 81 XS1100, 85 FJ1100, 96 GPZ11 (1200 EFI PROJECT), 03 VT11, 06 VT600, 12 ZX14R, 67 C20
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He will get u a decent flash, he did my zx14r and it rides so much better.

If rpm is hanging up but eventually comes back down, check ur vacuum lines. Sounds like a cracked line. Just enough leak to cause issues but not enough to make it wild. Also u might double check ur cam timing since i think u gotta pull them for valve adj. In fact go thru everything u touched and verify it is how its sposed 2 b. Even the little things that only got wiggled
 

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Discussion Starter · #9 ·
I have gone through and disconnected every hose, and reconnected new ones, hose clamps on all of them on both ends. Ive checked timing, 27 links in between marks, and marks are parallel with top of cylinder head. I feel I'm pretty diligent in following service manual, I've got 2 copies and both are well worn. Still having same symptoms. However there is a new issue. I thought maybe cam timing sensor on front of cylinders maybe bad so I swapped that out with the one from my parts bike ( also an 07 zx6) and now the bike won't get any spark. I'm just at a loss at this point. It was starting up right away and running, just with the hanging issue, but now it won't even get any spark. Wtf could cause this? All I changed was the sensor.....all help is appreciated guys. Thank you.
 

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I have gone through and disconnected every hose, and reconnected new ones, hose clamps on all of them on both ends. Ive checked timing, 27 links in between marks, and marks are parallel with top of cylinder head. I feel I'm pretty diligent in following service manual, I've got 2 copies and both are well worn. Still having same symptoms. However there is a new issue. I thought maybe cam timing sensor on front of cylinders maybe bad so I swapped that out with the one from my parts bike ( also an 07 zx6) and now the bike won't get any spark. I'm just at a loss at this point. It was starting up right away and running, just with the hanging issue, but now it won't even get any spark. Wtf could cause this? All I changed was the sensor.....all help is appreciated guys. Thank you.
What happens when you put the original one back in?
 

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Discussion Starter · #11 ·
I found it fellas. Little vacuum hose that connects to the bottom of the valve module for fuel on the top of the air box. Discovered the little hole on the bottom. Plugged the hose that connects to the other 2 on back of throttle body and voila
 

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Discussion Starter · #12 ·
So u guys were definitely on point, vacuum leak. Thank you for pointing me in the right direction. Greatly appreciated for y'all's help
 
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