Vn 750 Carb issue - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 7 (permalink) Old 07-20-2019, 06:20 AM Thread Starter
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Vn 750 Carb issue

1998 vulcan 750
I rebuilt heads new gaskets and all.
Got her running but the left side carb to front is blowing back major. Right side rear sucking away. If I put all the air connections back together I get a sputter backfire going on, temp fix is I disconnected the front from the rubber air shaft... running and no more sputter backfiring... gets up to temp.
Can't figure why one carb sucks and other blows. Carb was in 2 pieces when I bought the bike, is there an adjust to the carb that would cause this? It seems to be firing and getting hot, exhaust out of tail pipe...
Addition: today I pulled plugs one at a time, back loses power, front does not. So possibility my front is 180 degrees out? Possible thats why its blowing and not sucking?

Last edited by HipRick; 07-20-2019 at 01:40 PM.
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post #2 of 7 (permalink) Old 07-20-2019, 07:56 PM
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Sounds logical, but I'm not familiar with engine rebuilds.
Hopefully someone with more knowledge on this will eventually chime in.
Do you have a service manual?

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post #3 of 7 (permalink) Old 07-21-2019, 06:19 AM Thread Starter
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Have the manual... only so much use out of it. My idea is front is 180 out, that makes sense why carb is blowing not sucking. Just wondering if there is anything else I am missing, getting worn out dropping this engine out. Lol
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post #4 of 7 (permalink) Old 07-21-2019, 08:46 AM
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I would say yes, good chance the front cam timing is off. Any chance the two cams got mixed up?

Otherwise, it sounds like intake valves may be sticking.

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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

Last edited by Spockster; 07-22-2019 at 09:01 AM.
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post #5 of 7 (permalink) Old 07-22-2019, 07:24 AM Thread Starter
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no did them separately, but back is firing. Getting set to do a semi-quick drop and retime just from the top...I know the bottom gears were right on the money. going to only be 90 today 110 in garage, lol
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post #6 of 7 (permalink) Old 07-23-2019, 09:16 PM Thread Starter
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Dropped her, pulled tops off front and back... back lined up with flywheel R/mark.. which is the has been firing anyways. Rotated engine and reset front to F/timing mark on fly wheel... rotated engine a few times and every thing looks to line up... put her back in... still spitting
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post #7 of 7 (permalink) Old 07-23-2019, 09:24 PM
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Maybe try a compression test, seems like the intake valves may have a problem. Leaking or sticking.

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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