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Sorry I thought it had a rev limiter/ ECU Perhaps a jetting problem maybe some build up in the carbs all the boots are tight?

In a different thread a different poster was asking about a Vulcan's fuel petcock and multiple lines to it.

Which gives rise to the possibility for this problem that with loss of vacuum at high power settings, perhaps the fuel petcock is closing or partially closing and therefore cutting off the fuel supply.

If there is a Prime position on the petcock where the fuel supply is simply ON, try running that way and see if the high power cutout still occurs.

Vacuum operated petcock is to cut off fuel supply when parked but it could malfunction and give interesting symptoms.

Sorry I thought it had a rev limiter/ ECU Perhaps a jetting problem maybe some build up in the carbs all the boots are tight?

I made sure all the boots are tight. That was one of my guesses too but I can't hear air being sucked in from anywhere.

If there is a Prime position on the petcock where the fuel supply is simply ON, try running that way and see if the high power cutout still occurs.

It still happens in the prime position. No luck there.

Vacuum operated petcock is to cut off fuel supply when parked but it could malfunction and give interesting symptoms.

This is where I'm going to start looking if spraying ether at some joints doesn't cause revving to change. I'm really hoping this is it. This is driving me crazy.

Yep, it was the fuel petcock. I can't believe it. I had no idea that could cause the problems I was having. I cleaned it really well. Its still not perfect but its incredibly better. I think I'm going to replace the whole thing. Thanks to everybody for all your help, it was very appreciated. I can't thank you enough.

Jeffsg605 wrote:Yep, it was the fuel petcock. I can't believe it. I had no idea that could cause the problems I was having. I cleaned it really well. Its still not perfect but its incredibly better. I think I'm going to replace the whole thing. Thanks to everybody for all your help, it was very appreciated. I can't thank you enough.

So we can all learn more- what was it about the petcock that wasn't working right?

It must have been plugged. However now I'm reluctant to say that was it. It was running really well. Then I let it sit about an hour, started it back up, and it was running worse although not as bad as before I cleaned it. I took the petcock off and I'm going to let it sit in sea foam tomorrow and see if that helps.
Another weird condition I just noticed today though: the bike will idle fine on the kickstand but when I tip it up, the idle drops a few hundred rpm and then comes back. Any ideas on that one?
I really hope its just the petcock. I am getting sick of this bike.

Jeffsg605 wrote:It must have been plugged. However now I'm reluctant to say that was it. It was running really well. Then I let it sit about an hour, started it back up, and it was running worse although not as bad as before I cleaned it. I took the petcock off and I'm going to let it sit in sea foam tomorrow and see if that helps.
Another weird condition I just noticed today though: the bike will idle fine on the kickstand but when I tip it up, the idle drops a few hundred rpm and then comes back. Any ideas on that one?
I really hope its just the petcock. I am getting sick of this bike.

I'm wondering if you have a lot of gunk in the tank that hasn't yet been fully cleaned out.
Might want to put a small see-thru inline fuel filter between the petcock and the carbs to get more insight as to what's happening.
(lawn mower parts might be the right size if the auto parts store doesn't have what will fit)

Idle speed changing when you tip the bike up isn't necessarily a defect. The gas levels in the carb bowls change when you go from tipped to upright. There were a lot of things about carbs that we used to just live with. If it does everything else perfectly would this make you dump the bike? (I hope not)

Jeff, how did you go about cleaning the fuel tank?

I've never cleaned the tank. I only got the bike recently and it only started acting up after I replaced the stator. I guess I assumed the tank must have been fine. I'll run a little seafoam through that too though. Is there a better way to go about cleaning it you think?

Might want to put a small see-thru inline fuel filter between the petcock and the carbs to get more insight as to what's happening.

Not a bad idea. If the seafoam soak does nothing for me I will try that.

You can find lots of vids on You Tube (like this one) on cleaning gas tanks.