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Vacuum Leak

Old 07-01-2017, 12:03 AM
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Vacuum Leak

Hi Superhawk Forums again,

Is it possible to have a vacuum leak at the throttle shaft on this bike?

After fixing my 'misfire' issue, I am trying to pinpoint a vacuum leak on my superhawk and spraying around the front throttle shaft seems to be the ticket. So far I already replaced the front carb boot (no difference).

Also, could the carb cleaner possibly be being sucked back into the inlet from that area when I'm checking for leaks? I am pretty lost on what to check right now and I appreciate any help I get.

Thanks,
Nathan
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Old 07-01-2017, 03:40 PM
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Nathan,
I think it's highly unlikely that it's leaking there. Not saying it's impossible but I don't recall ever hearing of it happening.
I'd sooner believe your boots aren't sealed up and the spray is running down there.

If you believe that's the issue, find a replacement and swap it in to see if it remedies the leak. May be best to pick up a pair of new boots as well.
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Old 07-01-2017, 05:06 PM
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Pay attention to what the large weasel has to say.
You don't have cocaine eyes and you don't have sleepy jives what I think you have are nasty boots.
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Old 07-01-2017, 06:47 PM
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I definitely believe the nasty boot stuff, but the problem I have is that I changed out the front boot already chasing down this vacuum leak, which is why I'm stuck. I changed it just a few days ago with a brand new one. Also, the old one didn't have any cracks, even when flexed.

When I spray carb cleaner above the boot the idle still goes down despite the new boot.
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Old 07-01-2017, 08:37 PM
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Recheck everything you did. Do over again. Make sure it's right.
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Old 07-02-2017, 02:22 AM
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I think I'm going to change the vacuum lines soon because the current ones are cracking. I'll take the carb boots off and make sure the mating surfaces are good.

By the way I have actually taken the carbs off twice in the past week to make sure its all put back together right. All the hoses are hooked up properly and everything is seated well. Its really confusing, but hopefully I can catch whatever it is soon. The fact that the leak didnt go away when I replaced the front boot is extremely disheartening.

Thanks for the help. I'll keep posting updates when I get around to working on the bike again.
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Old 07-02-2017, 07:47 AM
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[QUOTE=nrowah;402975]I think I'm going to change the vacuum lines soon because the current ones are cracking. I'll take the carb boots off and make sure the mating surfaces are good.

By the way I have actually taken the carbs off twice in the past week to make sure its all put back together right. All the hoses are hooked up properly and everything is seated well. Its really confusing, but hopefully I can catch whatever it is soon.
Originally Posted by nrowah View Post
The fact that the leak didnt go away when I replaced the front boot is extremely disheartening.
and most likely diagnostic.


Originally Posted by nrowah View Post
Thanks for the help. I'll keep posting updates when I get around to working on the bike again.
Is the plug in place where the boost joint threads into? Or is there a boot joint with a hose attached?

Last edited by xeris; 07-02-2017 at 07:53 AM.
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Old 07-02-2017, 08:49 AM
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Is the plug in place where the boost joint threads into? Or is there a boot joint with a hose attached?
There is a joint with a hose attached right there. One to the front cylinder (goes to PAIR under airbox) and one to the rear (petcock). I havent removed PAIR.

I dont think its the problem because the dip in rpm gets worse as I spray closer to the throttle shaft, which is pretty far from the vacuum attachment, but I'll replace the lines anyways because they're cracking at the ends. Maybe it'll fix something.
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