Fuel/Air Mixture problems(I think) - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 4 (permalink) Old 08-31-2013, 07:27 PM Thread Starter
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Fuel/Air Mixture problems(I think)

Just trying to get some expert(or semi-expert) advice:

I recently bought an '86 vn750 with 14k original miles on it. It needs a little work since it's been sitting in a garage for several years, but I'm not sure what this particular problem could be.

The front head is not "engaging" properly. The fuel won't ignite without revving the bike to around 3500 RPM's, sometimes 4000 RPM's. And when it does ignite, the exhaust gases that come from the muffler etc are cool, instead of slightly warm.

There's also a mild backfire while decelerating.

Anyone have any suggestions on what the problems could be?
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post #2 of 4 (permalink) Old 08-31-2013, 08:11 PM
..have a vulcan good day!
 
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Quote:
Originally Posted by StrategicBlunder View Post
Just trying to get some expert(or semi-expert) advice:

I recently bought an '86 vn750 with 14k original miles on it. It needs a little work since it's been sitting in a garage for several years, but I'm not sure what this particular problem could be.

The front head is not "engaging" properly. The fuel won't ignite without revving the bike to around 3500 RPM's, sometimes 4000 RPM's. And when it does ignite, the exhaust gases that come from the muffler etc are cool, instead of slightly warm.

There's also a mild backfire while decelerating.

Anyone have any suggestions on what the problems could be?
Weak spark ? ?
Perform "Coil Mod" ...in verses.

'86 VN750 13,700 mi -Stock
-Purchased 2008 w/8800mi
Replaced ALL Cables . Kuryakyn LED Voltmeter
SilverStar Ultra 9003/HB2 H4 Headlamp, Jardine Fwd Controls,
Iridiums DPR7EIX-9 & Wires, Tuxedo Mod, Coil Mod, P/U Sensor Mod, Fork Seals,
Splines Lubed - 11/4/2012 - MF AGM Battery
Additional Flashing LED Brake Light on Trunk
Dampers went out @ 13+K !
After TOC MCCT's..... so amazingly quiet I discovered a rattling heat shield on my stock exhaust !
...have a vulcan good day!
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post #3 of 4 (permalink) Old 08-31-2013, 08:20 PM
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Since its been sitting, drain the tank and run SeFoam or equivalent....also, since its just the front.....drain the left side carb....do a backblow on it....(see the Carbs section for the sticky on the proceedure)....also, replace your plugs and check the plug wire condition....its either getting too much gas (sticking float, my guess), or has an insufficient spark to the front...often, overfilling the crankcase will cause the front not to fire.



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post #4 of 4 (permalink) Old 08-31-2013, 08:29 PM Thread Starter
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I've replaced the spark plugs, spark plug wires, battery and checked the voltage(while running, of course) on the coil. Spark-wise, the bike is fine. I'll do a blow back and run some Sea Foam through it and see if it helps. Thanks a lot for the info, guys. I'll update the thread if that was the issue or not and give more info if needed. Again, thanks a lot.
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