Less Choke May Help With Rear Cylinder Not Firing - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 6 (permalink) Old 04-17-2016, 07:07 PM Thread Starter
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Less Choke May Help With Rear Cylinder Not Firing

I have owned 3 Vulcan 750 motorcycles, a 1998 and two 2005s. This 2005 is the first Vulcan that I have owned that has had a problem with the rear cylinder NOT firing when the engine starts. What seems to help mine start and run on both cylinders is to start the Vulcan using less choke. If I fully choke it then the rear cylinder will not fire, especially when it is idling - like it is flooded. If it is revved up then it will fire but if the throttle is released, the rear cylinder will stop firing and the Vulcan will not idle. It does not clear up, even after a 10 mile ride. If the fuel line petcock is turned off then the rear cylinder will begin firing and it will idle but if the petcock is opened, it will fail to fire and fail to idle again. Very Weird. Once the rear cylinder does not run and consistently fire, the only way that I have been able to get it to fire again is to turn off the petcock and run the carbs out of gas. Then, after opening the petcock and with no choke, start it up. If you start it cold, use just a little choke.

So, in summary, what seems to work for me is if the choke lever is pulled down just about half way. Then when it starts up it is running on both cylinders and continues running well. The BIG differences between this Vulcan and my other two [which did not have this problem] is that this VN750 has V&H Cruzers and the carbs have been rejetted. Those two things could be factors. Does anybody have a stock VN750 with the rear cylinder firing problem?

So my tip is to start up the Vulcan without fully choking it. Just try about 1/2 choke and see if that helps you. You will have to find 'the sweet spot'. Once you find the best place for the choke lever to start the Vulcan 750 it may make a difference for you as well. By the way, using less choke will probably mean that you will have to crank the VN750 a bit more than usual.
Good Luck,
Sam

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post #2 of 6 (permalink) Old 04-17-2016, 09:16 PM
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Originally Posted by Sam612 View Post
I have owned 3 Vulcan 750 motorcycles, a 1998 and two 2005s. This 2005 is the first Vulcan that I have owned that has had a problem with the rear cylinder NOT firing when the engine starts. What seems to help mine start and run on both cylinders is to start the Vulcan using less choke. If I fully choke it then the rear cylinder will not fire, especially when it is idling - like it is flooded. If it is revved up then it will fire but if the throttle is released, the rear cylinder will stop firing and the Vulcan will not idle. It does not clear up, even after a 10 mile ride. If the fuel line petcock is turned off then the rear cylinder will begin firing and it will idle but if the petcock is opened, it will fail to fire and fail to idle again. Very Weird. Once the rear cylinder does not run and consistently fire, the only way that I have been able to get it to fire again is to turn off the petcock and run the carbs out of gas. Then, after opening the petcock and with no choke, start it up. If you start it cold, use just a little choke.

So, in summary, what seems to work for me is if the choke lever is pulled down just about half way. Then when it starts up it is running on both cylinders and continues running well. The BIG differences between this Vulcan and my other two [which did not have this problem] is that this VN750 has V&H Cruzers and the carbs have been rejetted. Those two things could be factors. Does anybody have a stock VN750 with the rear cylinder firing problem?

So my tip is to start up the Vulcan without fully choking it. Just try about 1/2 choke and see if that helps you. You will have to find 'the sweet spot'. Once you find the best place for the choke lever to start the Vulcan 750 it may make a difference for you as well. By the way, using less choke will probably mean that you will have to crank the VN750 a bit more than usual.
Good Luck,
Sam
You and "Camshaft" seem to have the same problem....
this is copied & Pasted from what I posted in his thread.....
...pasted.....
To me, This reads as Carbs....BUT.....
Although, in 2009-10 - I had a similar issue, replaced the Ignitor....problem resolved. - -
hope this helps...
- -

'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
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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 6 (permalink) Old 04-18-2016, 07:22 AM Thread Starter
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Thanks for the tip. That looks like a $300 item. I will try that most likely as a last resort because of the price. I saw a video of a guy on YouTube that shows replacing the 3 relays on the CDI and he sells them on eBay.
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post #4 of 6 (permalink) Old 04-18-2016, 07:26 AM
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Sounds like the float height could be too high.

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post #5 of 6 (permalink) Old 04-18-2016, 08:11 AM
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Or sticky float needle.either try Wolfie's backblow method or pull carbs and clean

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post #6 of 6 (permalink) Old 04-18-2016, 06:44 PM Thread Starter
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Thanks. Yes, I thought that it could be a valve and seat problem in the float chamber whereby the valve was not closing and it was allowing too much fuel to flow. However, it started up and ran fine today - but it could still be an intermittent float problem. I started it with about 1/3 choke today.

That is another good tip to try Wolfie's backblow method. If that rear cylinder fails to fire again I will give the carburetor a blow. That will be a quick and easy thing to do. Appreciate all the advice and possibilities.

That dual carb unit is a real pain to remove. Does anyone know if there are two replacement carbs available to eliminate the stock 'Siamese Twin' carb setup? I did not realize until removing them to rejet and clean them that they are two carbs in one shell and not individual units.

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