Petcock issues? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 9 (permalink) Old 07-03-2015, 04:40 PM Thread Starter
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Petcock issues?

Hey everyone! I hope you all are well!
so my Clymer manual trouble shooting for symptoms of not starting tells me to check the gas valve. I removed the hose from the carb and turn the valve to the on position and I have no gas flow. The same in the Res position. so I open the gas cap. still nothing happens. gas cap open and cranking the engine over still no gas flow. I had this apart may last year rode it all summer. could the petcock clog so soon? really just dont want to drain the tank and take it apart. is that my only option?
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post #2 of 9 (permalink) Old 07-03-2015, 05:36 PM
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Your first post, soooo, .... Welcome!

The petcock on this particular machine is vacuum actuated, so it should not flow gas unless there is vacuum applied on the center hose, the one that runs to the left side carb.

Doesn't take a lot of vacuum, test can be done by mouth if you don't have a mighty-vac tool.

Also, that vacuum line should never have gas in it. If it does, the petcock is leaking through it's diaphragm.

I think this vacuum petcock can lead to some cold start issues when the bike has sat for more than a day or two. Gas evaporates from the carbs, then it can a good bit of cranking to get fuel back into the carbs.

Could also be the enricher circuits aren't fully working. This carb doesn't have a conventional style choke setup.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
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Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #3 of 9 (permalink) Old 07-03-2015, 05:40 PM
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Quote:
Originally Posted by Spockster View Post
Your first post, soooo, .... Welcome!

The petcock on this particular machine is vacuum actuated, so it should not flow gas unless there is vacuum applied on the center hose, the one that runs to the left side carb.

Doesn't take a lot of vacuum, test can be done by mouth if you don't have a mighty-vac tool.

Also, that vacuum line should never have gas in it. If it does, the petcock is leaking through it's diaphragm.

I think this vacuum petcock can lead to some cold start issues when the bike has sat for more than a day or two. Gas evaporates from the carbs, then it can a good bit of cranking to get fuel back into the carbs.

Could also be the enricher circuits aren't fully working. This carb doesn't have a conventional style choke setup.
yup pretty much on target there. however, even here in the deep steamy SW of florida where I live, I can let mine sit for several days and I get immediate startup. so, the fuel isn't evaporating (not much anyway) from my carbs.

2005 VN750

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post #4 of 9 (permalink) Old 07-03-2015, 05:56 PM
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Might be a difference in where our vent is placed with the earshave. Mine is just tied to the frame under the tank, facing rearward. Maybe yours is on the gas sender cover?

Thought mine was predictable on cold starts, always go full choke. So I over filled the oil and was draining a little by taking the filter off and cranking it over. No choke, I never thought it would even fire, but it did right away. Actually tried to run, luckily the oil pan caught it all.

Takes a long time for oil to run down into the window when you add some, got in a hurry and overfilled it.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #5 of 9 (permalink) Old 07-03-2015, 07:04 PM Thread Starter
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Thank you everyone! I dont know why this expensive book is telling my that the vacuum hose should have gas flowing out... but you all hit the nail on the head. Working the vacuum hose manually I can hear gas bubbling through the lines, also the smell of gas. I am no mechanic I have learned way to much about working on motorcycles via this bike. its nice when it runs... after working the gas through manually It popped so... I think my main issue is when I took the carb off a few years ago I didnt put it back in the right position so now it has vacuum leaks, and maybe they are just progressively getting worse. so now I think its time to try to find the absolute correct position of the carb. the rear boot should be 15mm off center as far as the information I have looked up... but that doesnt even give me a picture of what it should be. So in conclusion I might be playing with the carb position for a few days. I hope I can fix this before the starter goes as all the tinkering with it I have noticed that seems to be getting weaker over time. Thanks again everyone!
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post #6 of 9 (permalink) Old 07-04-2015, 08:27 AM
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I thought I read some where the carb boots were marked. This picture is a little blurry but it may help.
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post #7 of 9 (permalink) Old 07-04-2015, 09:32 AM
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There was a post about the carb alignment marks in the past few months, Goofyfoot posted a larger pic there. Think it's a small tab on the boot, or triangle maybe? Might search through his posts.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #8 of 9 (permalink) Old 07-04-2015, 09:52 AM
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I did find this post: https://www.vn750.com/forum/showthrea...t=19929&page=3

And the search I used: https://www.vn750.com/forum/gtsearch....67490&ss=0j0j1

Sorry, I would look around more but the ad banners are making this site unusable for me, took me this long to scroll down a page. 20 minutes to look at two pages, that's pretty high tech!

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #9 of 9 (permalink) Old 07-05-2015, 03:10 PM Thread Starter
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Thanks for the INFO again guys! so glad to read all those posts. I though my inexperience was the reason that job was such a pain in the rear. I can breathe easy knowing that the carb removal is just a pain for everyone! now when I get the motivation i will go and take it all apart again. I might just wait till I can afford the K&N pods and new needles do an ear shave just to make the job that much easier.
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