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Discussion Starter #1
I have a 1998 Vulcan 1500 that's been sitting for two years. Wouldn't start at first but after draining tank, draining carbs and filling with pure seafoam for several days it will start with full choke only but dies right away. it will stay running with starter fluid but I did notice something strange, that air was blowing out of the air intake instead of sucking in. I'm hoping it's a vacuum issue or air is being sucked in from elsewhere aka air leak. when it does start and I keep it running with starter fluid, giving it any type of throttle causes it to die. Any thoughts on how to troubleshoot what the specific problem is?
 

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I assume it's a twin carb BUBF and not a single carb classic.

Are there any mods to the bike? The reason I ask id that if twin carb bikes have been modded with pipes, air and/or jetys, they can be a real nightmare to tune compared to a single carb.

At 19 years old, this bike is certainly ready for a carb tear down, cleaning and inspection of all the rubber bits if it hasn't been done already. You could have a stuck float, you could have a clogged fuel filter, you could have sediment in the jets , you could have cracked or stiff accelerator pump diaphragms, you could have cracked slide diaphragms. Since it stars with starter fluid, spark doesn't seem to be the issue, but fuel delivery does. Fuel pump could also be at issue. l would encourage you to get the carbs cleaned, and then tackle one issue at a time. If you try multiple fixes at once, you may not find out what the propbelm was, and you may end up making things worse and have no idea which change you made did it. Guess how I found this out. LOL

I also do not recommend running straight seafoam. It is a flammable solvent, not a fuel, and is designed to work diluted in gasoline or oil. A little bit goes a long way, and more is not always better. The same applies to carb mods, I found out. Little changes can make big differences.
 

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Discussion Starter #3 (Edited)
I should have mentioned I had a complete carb rebuild in 2015 as well as serviced the overall bike. It's twin carbs and tuning isn't the issue since it was running good two years ago with no changes since then other than sitting. No mods on this bike other than straight pipes which the previous owner put on, I'm assuming they changed the jets but forgot to check what was installed when they were rebuilt. Thanks for the advice on the seafoam, I won't do that again lol
 

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From my experience when a bike has been sitting for a length of time the fouling in the carbs as the old fuel wax's takes a lot of removal.
The very experienced mechanic at my local shop told me over a year of sitting the carbs will need to be stripped, ultrasonically cleaned and new seals, gaskets installed.
As part of that process you will need to remove the Jets and pilot screws to ensure that cleaning is through which then leads to having to reset the carbs from scratch.
I have a Bandit that was recovered from a shed after 10 years and it was a real labor of love to get the carbs sorted on that one.
My best advice is, get a specialist to do it or if you do it yourself read up on the topic, have all the replacement parts you may need for reassembly and take your time to do it or you may end up doing it 2 /3 times as the airways are very very narrow and the smallest bit of crud left over or debris shift will foul it again. Dont forget to check the tank and fuel filter as well.

Regards

Stu
 

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One of your valves may be sticking. I had a Roadstar that did that and I used seafoam SLOWLY poured into the intake to free them up. Worked wonders. You would have to have help with someone spraying starter fluid in to keep it running long enough to get the Seafoam to the valves though. There are videos on YouTube showing exactly how to do it.
 

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Discussion Starter #6
latest update is that I can start it up first try and it will idle great until the float bowls are dry then I have to restart it to get the bowls filled with gas. I tested the fuel pump and that works fine which leads me to believe it has to be the carbs. The puzzling part is why the float bowl fills when I use the starter but when it's just idling the fuel doesn't fill the bowls. must be something with the float or the float needle. I'm assuming that's causing the engine to die when any throttle is applied. I also checked both air/fuel adjustment screws and they looked fine...
 

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Pump only runs when:

1. Starter button pushed, or
2. Engine running.

Sooo, you are missing #2.

Did you have any contact with the fuel pump or its wiring?
 

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Discussion Starter #8
Pump only runs when:

1. Starter button pushed, or
2. Engine running.

Sooo, you are missing #2.

Did you have any contact with the fuel pump or its wiring?
I did and it was to test it with an ohm meter which it passed. I also tested it to make sure it's physically pumping gas. I'll post my most recent update which is it's running!
 

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Discussion Starter #9 (Edited)
Latest update, I fixed the issue! I chased so many potentially issues i finally found the problem and I'm glad I didn't prematurely pull the carbs. Front cylinder had no spark from either spark plug and the problem was a disconnected wire! Starts perfect, throttle revs great but it's running too rich I think. I see the manual indicates 2 1/4 turns out but are you supposed to adjust the pilot screw once it's warmed up and with no choke or does it not matter? I would think it would but want to confirm.
 
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