Troubleshooting why no fuel reaches carb on cranking - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 34 (permalink) Old 04-03-2016, 08:30 PM Thread Starter
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Troubleshooting why no fuel reaches carb on cranking

I am shopping used and checked a '06 vn750 I am seriously considering. Upon cranking it was not firing and I verified 0gas going to carb on kickstand side carb. yes, it had some fresh gas added at the time. The petcock was set at "on" but I also tried "reserve". Not a drop of gas when I disconnected the clear line to carb.

I put a light in tank and verified at least the upper portion was clean metal without rust. I need to take mirror and look further for sediment\rust as it was stale fuel.

I plan to visit the guy again and least put starter fluid in after plug pull to verify firing but wondering what would keep gas from being pulled upon cranking or a quick trouble shooting method?

Its a very clean bike with only 7,200 miles the lack of drive-off ability makes it affordable

2002 vn750
AGM battery, Shinko 230 tires oversized front
Ear shaved - k&n pods, drilled clutch basket
MCCT
40/138 jetting

If I can split a case and make it work - you can too!
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post #2 of 34 (permalink) Old 04-03-2016, 09:00 PM
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The good news is that there's not much to the system. With no prime position on the later fuel valves, the system only works with good vacuum. You can simulate that by popping the line off the carb and sucking on it if you're daring. A mityvac would do the trick also. If that doesn't cause fuel to come out, plan to replace the fuel valve. The blessing there is that you can use one from a TW200 which is dirt cheap and doesn't require vacuum. P/n is 23F-24500-20-00, should retail for about $16 plus shipping for a factory (not knock-off) unit.
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post #3 of 34 (permalink) Old 04-03-2016, 09:06 PM Thread Starter
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Thank you sir! I have happen to have a mity-vac type tool and didn't think of it. Will try.

So does the engine pull vaccum on the petcock when cranking or running allowing flow to the carb, or are you saying the carb sucks past the petcock valve? Are petcock valve on tank and fuel valve synonymous I presume?

2002 vn750
AGM battery, Shinko 230 tires oversized front
Ear shaved - k&n pods, drilled clutch basket
MCCT
40/138 jetting

If I can split a case and make it work - you can too!
Forum pictures:http://s150.photobucket.com/user/Gid...?sort=3&page=1
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post #4 of 34 (permalink) Old 04-03-2016, 09:10 PM
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The left carb has a vacuum hose on the side that runs to the petcock, it should never have fuel in it. The fuel lines are higher up.

Starting fluid might get it going, it worked on mine the first start after buying it.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
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post #5 of 34 (permalink) Old 04-03-2016, 09:17 PM
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The vacuum line from the carburetor pulls on the diaphragm in the fuel valve (aka petcock), releasing fuel to the lines to each carburetor. As Spockster said, there shouldn't be any fuel in the vacuum line itself.
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post #6 of 34 (permalink) Old 04-03-2016, 09:28 PM Thread Starter
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Makes sense - thanks for clarifying. Are the fuel lines easily accessible with tank installed

I guess its time to google diagrams or a manual to learn this setup.

2002 vn750
AGM battery, Shinko 230 tires oversized front
Ear shaved - k&n pods, drilled clutch basket
MCCT
40/138 jetting

If I can split a case and make it work - you can too!
Forum pictures:http://s150.photobucket.com/user/Gid...?sort=3&page=1
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post #7 of 34 (permalink) Old 04-03-2016, 09:32 PM
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It can take a bit of cranking to get one started after a long storage. It has to build vacuum then get fuel into the carbs and cylinders.

Corny gas can probably stick the petcock diaphragm too.

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 34 (permalink) Old 04-03-2016, 09:45 PM
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They're accessible at the fuel valve with the tank on. For the other end you'd need to pull the tank, but I don't see any reason you'd want to do so.
In the picture, the tube on the right with a hose clamp is a fuel line to one carb, the other tube is the vacuum supply.
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post #9 of 34 (permalink) Old 04-08-2016, 07:47 PM Thread Starter
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If old gas has the diaphragm stuck in petcock (as spockster suggested) what is the suggested solution?

When I remove tank, I thought I would try to apply vaccuum to petcock to confirm properly released gas so I can rule the problem further down line.

2002 vn750
AGM battery, Shinko 230 tires oversized front
Ear shaved - k&n pods, drilled clutch basket
MCCT
40/138 jetting

If I can split a case and make it work - you can too!
Forum pictures:http://s150.photobucket.com/user/Gid...?sort=3&page=1
gidaeon is offline  
post #10 of 34 (permalink) Old 04-08-2016, 07:58 PM
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Quote:
Originally Posted by calebj View Post
The vacuum line from the carburetor pulls on the diaphragm in the fuel valve (aka petcock), releasing fuel to the lines to each carburetor. As Spockster said, there shouldn't be any fuel in the vacuum line itself.
...so in the Prime position then... does moving to that position simply push the diaphragm out of the way?
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