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Discussion Starter #1
I have a '94 vulcan with about 25K miles. The bike has been running great with a couple of exceptions, which I'll explain shortly. The other day I was out for a ride for about an hour and I was cruising down the highway when suddenly, the engine started bogging down, losing power but not dying. After pulling over, the bike was still idling but would cutout when I gave it the throttle. I wasn't out of gas, I knew there was gas in the tank, but I switched to reserve and still no change. So I struggled to drive it about 10 miles back to the house. So now the bike still idles OK but cuts out when I give it the throttle.

But about 3 weeks ago it did the same thing while I was cruising down the highway but it only lasted about 1-2 minutes and it cleared up and was running OK again. I thought it was maybe bad gas. And about 3-4 months ago it did the same thing for about 1 minute, but then cleared up.

I've now replaced the spark plugs with no change, the old ones looked OK anyway. So I figure it could be a carb issue or a spark issue.

Is it possible that a coil or wire could give out at increased rpms but be ok while idling?

Does this problem sound like a carb issue even though the problem happens suddenly?

I appreciate any help, I really love this bike, other that these couple of issues I haven't had any problems with it, but now this has happened.
 

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Old Twistie Sticks Rider
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Check the Carb. vent tube in the right breather box, if not already done cut the tip at a 45* angle and replace in slot... Do the easiest & cheapest first...lol...
PS-Just noticed your first post... WELCOME...
Have a good one...Old Dog...
 

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..have a vulcan good day!
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Check for a possible POOG's issue.

:smiley_th +1
 

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Old Truck Junkie
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I had this problem. It would run good at the start. And than it would start to run on one cylinder. I found a bug in the petcock and some dirt in the carbs. Cleaned it up runs great.
 

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My first thought reading your description was POOGS. If it was the hose in the right ear it wouldn't go away, I don't think. But checking that hose and cutting at a 45* angle is just a good thing to do anyway.

And welcome!
 

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Prowling Tiger
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I don't think it's POOGS, either. Otherwise, you'd have more often. I'd say, drain the tank tank, pull off petcock and inspect and clean it. Then check your fuel lines for blockages. Another to try is back blowing the float bowls. There is a sticky on that under the carbs section.
 

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Old Twistie Sticks Rider
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My first thought reading your description was POOGS. If it was the hose in the right ear it wouldn't go away, I don't think. But checking that hose and cutting at a 45* angle is just a good thing to do anyway.

And welcome!
Exactly, and about the easiest thing to do first...
Have a good one...Old Dog...
 

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Discussion Starter #8
tried the cut, still the same

thanks for all the great tips, I cut the hose to a 45 degree angle, no change. So I removed the gas tank and opened the petcock to the normal centered position and sucked on the third outlet. Gas came out readily from one of the spouts but the other spout it just kind of dribbled out. Not sure if that's a valid test but I think I'm going to remove the petcock and make sure it's all clean. Dealing with the carbs will be a last resort, carbs and I don't get along too swell. I'll keep updating, thanks again.
 

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next time it happens...open the gas cap.
if it is POOGS, that will allow air into the tank...which in turn will allow fuel to flow again properly.

It's a very simple test....even easier if you have a spare key in the tank cap so you can do it while still running at speed.
 

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Prowling Tiger
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thanks for all the great tips, I cut the hose to a 45 degree angle, no change. So I removed the gas tank and opened the petcock to the normal centered position and sucked on the third outlet. Gas came out readily from one of the spouts but the other spout it just kind of dribbled out. Not sure if that's a valid test but I think I'm going to remove the petcock and make sure it's all clean. Dealing with the carbs will be a last resort, carbs and I don't get along too swell. I'll keep updating, thanks again.
Both outlets should have same amount of fuel pouring from them when vacuum is applied. If cleaning doesn't resolve things, disassemble the gas cap and clean out the shallow channels with a solvent like brake cleaner. Lube the tumbler mechanism while your in their, too. Doesn't take much torque to distort the keys. Even a slight twist will prevent the ignition from working. AND DON"T LOSE THE SPRINGS!
 

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Discussion Starter #11
have opened the gas tank

since this latest bout with this problem, I have added some gas and gas additive in the tank. with ya'lls help I'm gonna figure this thing out if it hairlips the governor.
 

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When I flow tested my petcock, gas would not flow from the rear outlet until you blocked the front. On my bike the front carb will fill first.
 

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Prowling Tiger
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When I flow tested my petcock, gas would not flow from the rear outlet until you blocked the front. On my bike the front carb will fill first.
Huh, there defiantly something screwy there. Defiantly take it apart and see if there is something obstructing the rear outlet. Could be the vacuum diaphragm is torn.

Let us know what you find. Oh, an easy way to drain the tank is to get a small diameter hose and syphon the gas out. Make certain the hose is at the lowest spot in the tank to get the most gas out. A lot easier and faster than sucking on the vacuum hose to the petcock. Doesn't look as ridiculous either.
 

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Discussion Starter #15
petcock was all clean

took apart the petcock and found no problems, so maybe there's something about what wmsonta also found. I also emptied the gas from the tank. Next I'm gonna get some seafoam to mix with new gas and run it through the carbs and engine.

Is there another common vacuum issue besides the hose running to the right ear that I can check out?

thanks again.
 

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Prowling Tiger
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took apart the petcock and found no problems, so maybe there's something about what wmsonta also found. I also emptied the gas from the tank. Next I'm gonna get some seafoam to mix with new gas and run it through the carbs and engine.

Is there another common vacuum issue besides the hose running to the right ear that I can check out?

thanks again.
That hose is not vacuum. It's a vent line for the carbs and it's only an issue if it falls out (durr, that's what she said!). There is a vacuum line running from front carb to petcock. I am not entirely certain where the rear carb vacuum line runs to.

Running seafoam is good. Something you might want to try is drain the float bowls of both carbs and refill them with seafoam. You'll need to get the spray can version to do this. Let the carbs sit over night and drain them again. Look HERE on how to back blow. The thread only talks about blowing air through the bowls; however take the spray can of seafoam, run the straw up into the drain nipple and fill it up. Keep a finger or 2 squeezed around the nipple while you spray to form a seal. Then close it off when you think (or if you have the rubber boots off, then visually see) seafoam is coming out of intake side of carb.

Good luck!
 

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I am not entirely certain where the rear carb vacuum line runs to.
That hose runs back to the air suction valve in front of the battery. If you do coasters, that port gets capped.
 

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Prowling Tiger
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That hose runs back to the air suction valve in front of the battery. If you do coasters, that port gets capped.
Maybe that's why I still get decal pops? I have the reed valves capped with 1/2" copper pipe end caps. It's not as bad as before, still present, though.
 

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Maybe that's why I still get decal pops? I have the reed valves capped with 1/2" copper pipe end caps. It's not as bad as before, still present, though.
Have you adjusted the air screws?

The vacuum would open the valve. If the valve is still hanging back there, it could be letting fresh unfiltered air into the intake, because another hose leads from the valve into the bottom of the airbox. The exhaust gases originally flowed from the heads, through the valve, into the airbox, then to the carbs.
 

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Prowling Tiger
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Have you adjusted the air screws?

The vacuum would open the valve. If the valve is still hanging back there, it could be letting fresh unfiltered air into the intake, because another hose leads from the valve into the bottom of the airbox. The exhaust gases originally flowed from the heads, through the valve, into the airbox, then to the carbs.
Yup, 2.5 turns out on both sides.
 
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