bike only runs on choke: can't diagnose the problem - Kawasaki Vulcan Forum : Vulcan Forums
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post #1 of 7 (permalink) Old 01-14-2019, 12:27 AM Thread Starter
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bike only runs on choke: can't diagnose the problem

I know that this is a common topic. I went down the list of usual suspects and couldn't come up with anything. There is a back story to this:

When I first bought the bike used, it never needed choke, even for warm up (this is in Southern California weather). Over the years it needed some choke when first started. One day I decided to I adjust the valves on the bike, following an excellent outline here on the forums - I adjusted them to spec. At the same time I also cleaned the carbs and rebuild them using a kit off Amazon. When I put it all together, the bike ran perfect, not requiring any choke when starting. I left it in the garage for a couple of months (too busy to ride). One morning I wanted to take a ride and found that it was running rough on idle. When attempting to take off it just stalled. It was able to idle loud on choke and rough at half choke. I took the carbs apart again and cleaned them. No improvement. I believe that I did an excellent job at cleaning the carbs.

Thinking that there may be a vacuum leak I have used a can of WD-40 and sprayed around the cables, the boots etc. None of this made the Revs go up. I made a youtube video on this:

Also I have verified that the petcock is flowing fuel freely (disconnected fuel line from cabs, opened the petcock to PRI and fuel just poured out. The bike runs the same on PRI or ON modes. Finally I have Stabil in my fuel so I don't think it's the gas. What do you guys think could be the issue?
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post #2 of 7 (permalink) Old 01-14-2019, 06:44 AM
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Usually when bike only runs with choke on you have a plugged pilot jet curcuit.

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post #3 of 7 (permalink) Old 01-14-2019, 10:49 PM
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Check the carb bowl vent and hose. A plugged hose will not let the fuel level stabilize in the bowl.
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post #4 of 7 (permalink) Old 03-22-2019, 08:21 PM
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Originally Posted by Blaine View Post
Usually when bike only runs with choke on you have a plugged pilot jet curcuit.
My 2009 runs fine once engine is warmed up, but always wants to start with the choke on (warm days might start with no choke, or with 1/2 choke; cold days prefers full choke). After riding with 1/2 choke for about 3/4 minutes, happy to run without issue on no choke.

Is this typical? According to the manual when the weather is warm enough it should be happy to start on no choke, but mine doesn't like that.
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post #5 of 7 (permalink) Old 03-22-2019, 08:31 PM Thread Starter
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I recall that when I first bought this bike, it never need a choke - regardless of ambient temperature (this is Southern Cali so you can imagine our range). As years went by, the bike demanded to be warmed up on choke more and more, eventually even in Spring/Summers. After I cleaned and rebuilt the carbs and adjusted the valves (they were within spec so I don't think that was the issue), it began to start up perfectly without choke on. It was only after another long stay in the garage without riding that the problem I outlined above has happened.
@budwizest : consider doing some carb cleaning. I found it to be a fun and easy process. The Haynes maintenance manual really helped.

Anyway, I just recently sold the bike as is. The lucky buyer will work out the engine issue himself with the info I provided him. I plan to take up road cycling as my 2-wheel hobby for the foreseeable future.
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post #6 of 7 (permalink) Old 03-25-2019, 07:14 AM
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budweist - Mine is the same.
When its really warm I can start with no choke but its a slow idle for awhile, so on warm days I just go half choke for about half minute so it runs smoother/faster and gets warmed up well.
Now when its cold I need full choke and that's what a choke is for. To get the engine started and running faster so it doesn't die when its cold.
To not use a choke when its cold ( under 70) is just not usual. There are exceptions and I'm sure posts will follow -----


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post #7 of 7 (permalink) Old 03-25-2019, 11:26 AM
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As a suggestion, once you have this resolved you might start using alcohol free gasoline if you don't already. I have found the alcohol in the gasoline is hard on the fuel related parts on many engines. Good luck !
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