Need Trouble Shooting Help! - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 21 (permalink) Old 09-27-2010, 01:41 PM Thread Starter
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Need Trouble Shooting Help!

I've got a 94 with about 12,000 miles on it. I have been fighting what I always thought were fuel issues. The bike usually starts fine but then idols weird, doesn't increase in rpms and wants to die even with the choke left on. To keep it running I have to keep the rpms up with the throttle. These are thing that I have done to try and get rid of the problem

1. Sea Foam
2. New sparkplugs, gapping and cleaning sparkplugs.
3. Pulled the carbs and cleaned them without splitting.
4. Along with three, drained tank, removed petcock and cleaned screen.
5. New air filters.

After the carb pull and tank cleaning it started right up and ran like a different bike. It sat for two weeks and Saturday it was back to the same old thing. Sunday it started right up but still idled slow. while it was trying to die I removed the front plug wires and realized that the performance did not change, reattached them. Removed one rear wire and performance went down, reattached. Shut the choke off and the bike died. The left pipe for the rear cylinder burned my fingertips and the right or rear one was cold. I removed the plugs and found that the front ones were wet or fouled and the rear ones looked ok.

Right now I have the front and side covers off and am trying to troubleshoot for an ignition problem. What I can't figure out is why my problem is intermittent. If I had the money I think I'd be looking for a replacement.

I have the Kaw Manuel but none of the ohm readings I'm getting on different components match the book. Does the Kaw voltmeter really get the reading in the book?

Any trouble shooting advice you can give would be greatly appreciated.

94 with @ 8500mi
AGM Battery
Willie and Max sm. slant bags
Memphis Shield
Splines lubed
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post #2 of 21 (permalink) Old 09-27-2010, 04:35 PM
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Some folks have trouble with the gas take breather hose. Gets clogged and fuel can't flow.

DT

95 VN750 (eBay)31k+
GL1100 front fender
OEM engine guard
OEM high back rest
'V-Twin' HWY pegs
Black 750 Spectre handlebars
SunPro Volt Meter (Amazon)
Maier bug shield (JCW)
Bar Ends anti-vibe (JCW)
Emgo air filters
Tank bag-Eclipse
Tail bag-FroZone Cooler
Back Rest-Igloo 6 pak cooler
WalMart Saddle Bags
R/R Relocate
Dry Splines Lubed
AGM DieHard-Sears
Gutted Goat
Sporster XL Mufflers
LED's-stop,tail,turn,marker
Pickup coil mod to .45mm
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post #3 of 21 (permalink) Old 09-27-2010, 06:05 PM
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This may be a dumb question, but gotta ask to be sure..... have you tried adjusting the idle knob?
Might not hurt to get the carbs sync'd even though ya didn't split 'em.
A home made manometer to check them is easy to make.


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Aim for the apex."

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post #4 of 21 (permalink) Old 09-28-2010, 04:58 AM
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It sounds like you are losing spark to the front cylinder when the ignition components warm up.

Pull the front plugs and check for spark when cold. From your description, it should have spark. Reinstall plugs and warm up until front cylinder cuts out. Check for spark again.

Also check resistance of the pick-up coils, and the ignition coils when cold and again when they are warmed to at least 70*F, or when the front cylinder cuts out.
Specs are in my Clymers manual, and I assume in the Kawi manual too. Depending on what you find, there are mods that can be done to one or both to strengthen the spark.

The service manual says a special Kawi ohm meter must be used to test the ignitor unit. Any other will give unreliable readings. For this reason the ignitor is usually only able to be tested by replacing it with a new, or known good one.

Here is a link that may help you. There are a couple of other links in that one too.
https://www.vn750.com/forum/showthrea...on+pickup+coil

Gordon

1991 VN 750 -"Cosmic Lady" or "Bad Girl"?
Purchased May 16, 2008
Approx.19,300km (12,000 miles)

H-D windshield
Relocated R/R
MF-AGM battery
Fiamm Freeway Blaster horns
F&S luggage rack and engine guard
Kury Offset Hiway pegs
July 13, 2016, Riding on the DARKSIDE now, Classic Radial 165/80-15


TOP TEN THINGS A NEW RIDER/OWNER SHOULD DO. Click on link.
https://www.vn750.com/forum/11-vn750-general-discussion/9127-top-ten-items-you-would-suggest-new-owner-do-his-new-ride.html
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post #5 of 21 (permalink) Old 09-28-2010, 10:55 AM Thread Starter
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Hyperbuzzin, in the past three or four years dealing with this intermittent problem, I have used the idle adjustment knob to up the rpms, so that when pulling up to a stop I can use both brakes without stalling out.

Gordon, thanks for the attached links. I've read them over this morning and plan on doing more testing to find out what's at fault. I always try to expect the worst. Maybe it's just a short. It sound like when the electronic parts go they just stop working. My problem goes away for a while then comes back.

94 with @ 8500mi
AGM Battery
Willie and Max sm. slant bags
Memphis Shield
Splines lubed
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post #6 of 21 (permalink) Old 09-28-2010, 04:44 PM
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I ran into something like that a few yrs ago.
Check that you have power to both coils, my back one was getting power but front wasn't getting anything. Found out it was the JB. The PO had spilled acid and it shorted out the JB. Idled OK on the rear but no power. Front cold rear good n warm.

Charlie
VN700 project bike 98% completed!!
68 Bushwhacker this winters project (in the works)
86 Honda GL1200i (winter project #2)
82 kz440 daily rider for now!


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post #7 of 21 (permalink) Old 09-28-2010, 07:14 PM
'03 VN750 "Rosie"
 
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Quote:
Originally Posted by bullwinkle View Post
I ran into something like that a few yrs ago.
Check that you have power to both coils, my back one was getting power but front wasn't getting anything. Found out it was the JB. The PO had spilled acid and it shorted out the JB. Idled OK on the rear but no power. Front cold rear good n warm.
For the rest of us amateurs, what is a JB and a PO? Junction Box?

'03 VN750 "Rosie"
Purchased in June 15, 2010
Windshield
Lubed Splines
Lubed and Adjusted Clutch Cable, Throttle Cables.
Relocated Voltage Regulator
Brakes Bled
Luggage Rack
Lazy Rider Bag
Leather Saddle Bags
Legitimate Title!! (finally!) Aug 30, 2010
New AGM Interstate Battery Sept 15, 2012

2008 Hyosung GV250 (sold!)
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post #8 of 21 (permalink) Old 09-28-2010, 10:09 PM
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Junction Box
Previous Owner

Charlie
VN700 project bike 98% completed!!
68 Bushwhacker this winters project (in the works)
86 Honda GL1200i (winter project #2)
82 kz440 daily rider for now!


A few clowns short of a circus now aren't we?
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post #9 of 21 (permalink) Old 09-29-2010, 09:30 AM Thread Starter
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I plugged all of the electronic components back in to check for a spark. Both plugs on the front cylinder spark and appear as strong as the back. I cleaned the front plugs and then started the bike. It starts right up but only the back one is firing. Hyperbuzzin mentioned syncing the carbs. I think I'll try that next. I just don't understand why it is an intermittent problem.

94 with @ 8500mi
AGM Battery
Willie and Max sm. slant bags
Memphis Shield
Splines lubed
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post #10 of 21 (permalink) Old 09-29-2010, 06:33 PM Thread Starter
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Before screwing with the carbs i decided to go ahead and start it up again. Fired right up with only the back one running. I upped the throttle a little at a time and at around 3000rpm the front cylinder kicked in and it evened out. I shut it down when grayish black smoke started shooting out of the pipes. To me it looked like both. I was going to check the compression but I don't have the right fitting for my tester. I'm hoping the smoke was because it wasn't warmed up enough. What do you guys think?

94 with @ 8500mi
AGM Battery
Willie and Max sm. slant bags
Memphis Shield
Splines lubed
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