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Concert connoisseur
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Discussion Starter #1
is it better to turn the gas off when not riding or is it ok to just leave it on all the time? I bought mine from my sister and her boyfriend who is a seasoned rider says there is no need to turn the gas off. does this sound right?
 

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Premium Member
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Yes. Our bikes have vacuum operated petcocks, so when there's no engine turning, there's no fuel flow. Unless your sister changed it from a vacuum to a gravity feed, you're ok. :) (see my new thread, however...)
 

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Love My Baby
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1,165 Posts
I always turn my petcock off when I park my baby, because if someone were to steal her by forcing the ignition on, they wouldn't get very far. I doubt the person stealing my bike would know about the petcock. And I don't think it can hurt to turn it off. Just remember to turn it on BEFORE you start it up, or you may forget and start running out of gas very shortly!
 

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Anyone smart enough to be able to steal the bike will know about petcocks.
 

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Love My Baby
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Anyone smart enough to be able to steal the bike will know about petcocks.
Possibly, but not where I'm from (Miami/Ft. Lauderdale). It's mostly kids who steal cycles and cars here. They're smart enough to break in and start cars, but they make stupid mistakes and get caught a lot because of them. They're often high and don't think straight either!
 

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True that. Too bad the kids and others think it's OK to take someone elses stuff. Damn drugs.
 

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On the vacuum petcocks you can't turn off the gas. It does no good to turn the lever. Remember that the only positions on the petcock are Prime- On- Reserve. When you turn the lever you are putting it to reserve or prime.
 

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Love My Baby
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I must have a gravity feed then. My 3 positions on the petcock are OFF, ON, RESERVE. By the way, does anyone know exactly how the reserve works, like how is the gas separated in the tank, and how does the valve select from ON to RESERVE? I always like to add to my knowledge base.
 

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On the vacuum petcocks you can't turn off the gas. It does no good to turn the lever. Remember that the only positions on the petcock are Prime- On- Reserve. When you turn the lever you are putting it to reserve or prime.
From 85 - 91 (I think thats the ending year) had res-on-prime after 91 they dropped the prime and went to Off.


rubyrick, Only if someone changed your petcock, then you have a vac and not gravity fed.
 

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I don't ever close mine, not on this bike or my last 3. The couple times I did for some reason, I always forgot to turn back on and then was reminded as I was blasting down the road....

And the reserve in the tank is just a small tube sticking up from the valve...
 

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Sparky!!!
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On the vacuum petcocks you can't turn off the gas. It does no good to turn the lever. Remember that the only positions on the petcock are Prime- On- Reserve. When you turn the lever you are putting it to reserve or prime.
If this is so..how come when I turn off the fuel...the bike burns the fuel in the carbs then dies???
 

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San Diego Vulcan Rider
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163 Posts
A previous post just said it was changed after '91. You have a '92, right?
 

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San Diego Vulcan Rider
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BTW: Anyone have an opinion as to which petcock is the better design?
 

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Super Moderator
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BTW: Anyone have an opinion as to which petcock is the better design?
Better?

Neither really. Most of the problem is the placement..the tank angles down to the back of the bike, so even after you run out of gas while on reserve..you still have gas in the tank...thus, a bad design.

I like the idea of the "prime" as it allows you to pull of a fuel line and drain some gas when the bike is not running. ( A wonderfull on the spot hand cleaner if you just stopped to fix some pretty womans flat)

But then again, having a "off " can be very handy when the petcock starts leaking..

So, if both types are working the way they are designed...meaning they only flow gas when the engine is running...I'll take the one with the Prime function over the Off position.

But that's just my opinion...

KM
 

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Didn't know that Kaw had changed to the ON/Off petcock. There are still using the vacuum petcock on there atv's. So, I though that it was still in use on the bikes. I like the ON/Off petcock better that the gravity one. This way I know that the fuel is turned off during the winter. I know that it has fuel when trying to start the bike after it has been sitting for some time when it get's hot and the gas might dry up.
 

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Didn't know that Kaw had changed to the ON/Off petcock. There are still using the vacuum petcock on there atv's. So, I though that it was still in use on the bikes. .
Just so you understand here, the on/off petcocks still require a vacuum line to work. They are NOT gravity feed. Only the "Prime" function on the older petcocks would bypass the vacuum switch and let gas flow without there needing to be negative pressure from the engine.

KM
 

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when I dissasembled my bikes's petcock there was not a spring behind the vacumn diaphram as pictured in the on line manual. Is the spring a change from 89 or is it missing the spring?
 

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You are missing the spring.
 
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