Hard starting when Hot - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 23 (permalink) Old 03-08-2016, 08:42 PM Thread Starter
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Hard starting when Hot

Hello everybody ,
I recently purchased a 92 with 20,000 miles. I have an Agm battery that was tested good. I replaced the plugs with the recommended NGKs. It usually starts ok when cold. Full choke n blip of the throttle it starts ok. Took it out for a ride and stopped at the gas station the bike was warmed up by this time but Wouldn't start. It cranked and backfired but wouldn't start. I tried with and without choke and blip the throttle still wouldn't start. 10 min later it Finnaly started then stalled then I got it going again. What are my options here? Is this a carb issue? This is my first bike and I'm ok with doing any work myself I just don't know what to do. I don't want to get stranded somewhere. Thanks in advance for any suggestions.
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post #2 of 23 (permalink) Old 03-08-2016, 11:48 PM
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Try it without opening the throttle. If it doesn't start, try the choke with no throttle. Mine refuses to fire up hot with the throttle opened, and needs choke after sitting a short time. Backfires sometimes if I open the throttle and crank long enough.

https://www.vn750.com/forum/19-electr...ire-mod-6.html could possibly help.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
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post #3 of 23 (permalink) Old 03-08-2016, 11:50 PM
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Hot starting issue is usually solved with the pickup coil mod. The two wire mod helps overall power, too, and the ignition relay mod helps ignition power. I did all 3!

1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
TOC MCCTs
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Tuxedo Mod
Rebuilt Forks w/ Progressive Springs
V&H Cruzers
VN750.com Grill Cover
Meanstreak Seat
Emgo 23-92411 Handlebars
MOSFET FH012AA R/R


1990 Kawasaki Vulcan 750

1998 Honda VFR800 FI

2014 Honda VFR800F

1989 Pontiac Firebird Formula 350
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post #4 of 23 (permalink) Old 03-09-2016, 06:19 AM Thread Starter
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Which of those 3 mods shouuld I start with? So you don't think it has anythjng to do with the carbs? Fuel being to rich? Thanks
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post #5 of 23 (permalink) Old 03-09-2016, 08:32 AM
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I'd do the pickup coil mod first. And Seafoam the crap out of it.....then go from there if still issues.

Mine started best when hot without using the throttle also, although you need to crank it open as soon as it catches.

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post #6 of 23 (permalink) Old 03-09-2016, 09:40 AM
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I wouldn't think it would be too rich, too lean would my first thought. The backfire is most likely caused by a lean mixture or errant spark at the wrong time. Open throttle = more air, more air = leaner mixture, lean mixture = lean pop.

My reasons for linking improved hot starts with The Two Wire Mod are listed in the first post there. (improved voltage to the IC Ignitor)

edit: Have also seen electronic ignitions release an errant spark when there is low voltage, or the the current is suddenly cut off.

The Two Wire Mod involves, in part, the start circuit, bypassing the start relay in the JB, and the yellow/red wire that runs to the IC Ignitor off that same circuit.
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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; 03-09-2016 at 10:42 AM.
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post #7 of 23 (permalink) Old 03-09-2016, 02:43 PM Thread Starter
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Spockster with the 2 wire mod do I just remove those 2 wires and connect them together? Little confused because I seen a picture where the guy cut his wires. Thanks
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post #8 of 23 (permalink) Old 03-09-2016, 04:35 PM
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Originally Posted by Munchy View Post
Spockster with the 2 wire mod do I just remove those 2 wires and connect them together? Little confused because I seen a picture where the guy cut his wires. Thanks
Best to cut the two wires, and leave enough on the plug in case you need to put it back. Some have had their headlight quit after doing the mod. However, I never did get an answer to confirm if the mod was done right.

I left about 1.5" sticking out of the plug then covered them with shrink tubing and tape.

I did pull the spades out of the plug just to try the connection. Once I knew it worked, I cut them off.

The mod is a good preventative measure in three ways. Reliability for the start circuit, bypassing the troublesome Junction Box, and preventing charge system brownout or failure.

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 23 (permalink) Old 03-10-2016, 06:07 PM Thread Starter
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Problem... I started thr pickup coil mod. Was surprised to see that each of mine were only attached with one screw not two. Thr top screw on the top coil and bottom screw on bottom coil are gone. There's no where even for them to screw into... now what?
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post #10 of 23 (permalink) Old 03-10-2016, 08:07 PM Thread Starter
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just put it all back together and it starts up great now my big concern is since there is only one screw holding each of those in place instead of two what happens if they loosen up... if something happens n they come in contact with the rotor then what ... I don't see this as being safe...
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