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Discussion Starter #1
Hey guys, in need of some help asap, while I was out on my ride today I had no problems till heading home, randomly one of the cylinders stopped firing, it helped a little when i shifted down but after a min or two of riding it cleaned up. any ideas of what could be wrong? my guess is there is a problem somewhere in the ignition system. i would greatly appreciated. oh and also it sometimes misses during warm up but never like this before.
 

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Dirty carb? Can try Seafoam in the tank and ride it.
 

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Discussion Starter #3
i thought it could be a fueling issue, i also found that the rear cylinder missfires at idle. i got some carb cleaner as well as a can of seafoam. im also doing a spark plug change. im going to try to adjust the idle mixture on the rear cylinder to see if i can clean up the idle a bit.
 

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Discussion Starter #4
after changing plugs, running a can of seafoam through the engine and adjusting the idle screw it cleaned it up a bit but it still has periodic issues.
 

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The Vulcan 750 has a weak ignition system and needs plugs in good condition. But if it starts fairly easily, it is probably not the plugs. Plugs wear and get dirty, and develop internal resistance over time. But they never get worse, and then better again. It is common for the Vulcan 750 to start up on one cylinder after sitting a few days, and run that way for 15-20 seconds, sometimes longer. I have know idea what the cause is, all three of mine have done it, with new plugs. I'm fairly certain it has to do with the carburetors, but I don't know what exactly what. It could be the petcock. For some strange reason, there is a separate fuel line from the petcock to each carb. Maybe it takes longer for gas to come out of one side of the petcock than the other.
 

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after changing plugs, running a can of seafoam through the engine and adjusting the idle screw it cleaned it up a bit but it still has periodic issues.
What sort of issues, and in which period?

Sometimes you just have to bite the bullet and clean the carbs the hard way.

One trick to use, is pulling the choke on when the engine is acting up while moving. If it runs better, it's starving for fuel. If it dies out, it's probably getting enough fuel.

Headed out one time for 150 mile ride. Happened to have the tank full of seafoam/gas when I left. Quarter of the way into the trip, one cylinder went dead at a certain rpm range. I could choke it and get full power, so I kept speeding up, then with choke off let it slow down to the point where it bogged out. I'd hold the throttle open and let it bog at 45mph for about a mile at a time, then pull the choke and catch up to the group. In 25 miles it was running great again.

Maybe ride some more miles with seafoam?

I've also had my carbs off once, pilot jet was clogged solid. From idle to mid-range, taking off or slow cruise, it only ran on one cylinder. Had the idle adjustment cranked up to make it idle on one cylinder, about double the normal setting. If the dead cylinder fired up while turning a corner, it would nearly crash me.

Still running the same Denso plugs that came with my bike, I've got 6000 miles on them.
 

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Check the electrical connections on the ignition coils. I had my bike bucking like a bronco because one of the spade connectors came looks on the front coil, so the front cylinder was dying intermittently. Re-connected the spade connector to the coil and VOILA, no more problem.
 
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