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VN750 General Discussion

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post #11 of 32 (permalink) Old 09-30-2019, 01:07 AM Thread Starter
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Originally Posted by Sparkys73150 View Post
I know it sounds crazy but, I have a 19hp B&S engine on my wood splitter it was running fine. I welded something on it and when I tried to start it, I got nothing. I changed everything I could think of. I remembered I didn't change the spark plugs. put new plugs in and bingo!!! You might try a set of plugs.
Sound advice however the plugs i have are brand new. They were the first thing i could rule out. There is only 4 things left i can try. Starter rebuild, new carb rebuild kit, switch pickup coils like spokster said and a rebore. After that i am out of options as everything else checks out..
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post #12 of 32 (permalink) Old 09-30-2019, 05:05 PM Thread Starter
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Ok lads upon taking spockters advice i checked the pickup coils. Right, from what i gather on other threads i have them in the wrong location and should be switched the other way. Can anyone confirm this. Not sure why the pic is sidways tho. The left side is the top
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post #13 of 32 (permalink) Old 09-30-2019, 05:58 PM
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Originally Posted by Will750 View Post
Ok lads upon taking spockters advice i checked the pickup coils. Right, from what i gather on other threads i have them in the wrong location and should be switched the other way. Can anyone confirm this. Not sure why the pic is sidways tho. The left side is the top
Yes, they look reversed. A bit hard to see the colors in the pic, but I can tell the black/yellow wire is in the wrong place.

According to the repair manual: VN750_Vulcan_Service_Manual_Parts_Catalogue

Rear cylinder wire colors: black/white and black/red at the top position (rear cyl)

Front cylinder wire colors: black/yellow and black at the bottom position (front cyl)

Swap them around and it's gonna start right up!

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

Last edited by Spockster; 09-30-2019 at 06:06 PM.
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post #14 of 32 (permalink) Old 10-01-2019, 02:43 AM Thread Starter
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Lets hope so. I have them swapped so i will hopefully start it today. How i never thought of checking them in the first place is beyond me. Its always the small things aint it. I will keep you posted.
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post #15 of 32 (permalink) Old 10-01-2019, 03:20 PM Thread Starter
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Quote:
Originally Posted by Will750 View Post
Ok lads upon taking spockters advice i checked the pickup coils. Right, from what i gather on other threads i have them in the wrong location and should be switched the other way. Can anyone confirm this. Not sure why the pic is sidways tho. The left side is the top
Yes, they look reversed. A bit hard to see the colors in the pic, but I can tell the black/yellow wire is in the wrong place.

According to the repair manual: VN750_Vulcan_Service_Manual_Parts_Catalogue

Rear cylinder wire colors: black/white and black/red at the top position (rear cyl)

Front cylinder wire colors: black/yellow and black at the bottom position (front cyl)

Swap them around and it's gonna start right up! [IMG class=inlineimg]/forum/images/smilies/smile.gif[/IMG]
ok so i went to start it up today. Never started only backfires really loudly. Near damn popped my ear drum. Lol. However it did run for a second while i held the start button but as soon as i let it go it cut out again. Its really close but not close enough. I tried starter flued also with the same results.
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post #16 of 32 (permalink) Old 10-01-2019, 04:41 PM
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You getting the “thump thump BANG!!!”? All these attempts can be eating away the battery
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post #17 of 32 (permalink) Old 10-01-2019, 04:49 PM Thread Starter
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You getting the “thump thump BANG!!!”? All these attempts can be eating away the battery
yes. Its a brand new battery. Bit puzzled as to why its not starting. Even more puzzled the fact that it started while holding the start button but as soon as i let it go the bike died.
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post #18 of 32 (permalink) Old 10-01-2019, 07:19 PM
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Do you have a voltmeter to read the battery voltage? It could be weak by now if hasn't been charged at all.

Is there any chance the cam timing is still off?

How long did it run while holding the start button? Would it rev up, or just fired a bit more? How well was it running? The start button has a wire connected to the CDI box, consensus here is that it alters the ignition timing during starts. (could be the reason for backfire on low voltage starts)

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 #19 of 32 (permalink) Old 10-02-2019, 01:26 AM Thread Starter
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Originally Posted by Spockster View Post
Do you have a voltmeter to read the battery voltage? It could be weak by now if hasn't been charged at all.

Is there any chance the cam timing is still off?

How long did it run while holding the start button? Would it rev up, or just fired a bit more? How well was it running? The start button has a wire connected to the CDI box, consensus here is that it alters the ignition timing during starts. (could be the reason for backfire on low voltage starts)
No i dont have a voltmeter. However the battery was not fully charged but i did connect to a car battery. As for cam timing, i set it exactly to the instructions in the downloadable manual. It only ran for a few seconds as i didnt want to keep the start button pressed to long and damage the motor. It would not rev at all. Do you think it could be to do with the cdi box?. I will fully charge the battery today and see was that the problem. So plan today is clean plugs, drain carbs (just incase), fully charge battery, recheck all connections and im also trying to locate a gauge to measure compression. Fingers crossed.
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post #20 of 32 (permalink) Old 10-02-2019, 01:31 PM
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Can't rule out the cdi yet. Not sure what tests there are for it, check the manual.

You have decent spark, but is it at the correct time.

Something about the start button, it means something, but on this system I'm not sure what. That symptom has been mentioned here before, but I'm not sure if anyone ever posted their fix. Never hurts to try the forum search.

Sometimes on old points ign systems, running only in the start position, meant a defective ballast resistor. But the ballast resistor on those old systems was there to keep the points from getting more than 9v, to reduce burning of the contacts. Could be something similar happening in the CDI, because there is that white/red wire between the start button and the CDI. The ignition timing could be going numb when you release the start button.

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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