Internal carb leak? (formerly "cracking the throttle kills it")

[QBS]

I vote for the Presto Chango holes.

[Rick G]

 may have a body , was it front of rear?

[Jimustanguitar]

may have a body , was it front of rear?

I need the rear.  Thanks for taking a look, Rick!

[Rikugun]

Since you're gonna have the carbs off I'd still encourage you to consider new shaft seals. When I changed mine, they were loose in the casting and had no appreciable grip on the shaft. While cdnlouie's comment is correct regarding outside air pressure working to seal the lip in use, that's not to say they wouldn't be capable of stopping a trickling of fuel with the engine off.

He once advocated changing them out and suggested many Visions would benefit from the new seals. Perhaps he just objects to my conclusion that leaking fuel past the (static) seal was indicative of a bad seal? Even if my conclusion is wrong, I'd still think 30 year old rubber is no longer providing the seal that was intended. Just my 2 cents. Here's a discussion on the topic:
http://ridersofvision.net/rovforum/index.php?topic=6017.msg117298#msg117298

[Jimustanguitar]

Since you're gonna have the carbs off I'd still encourage you to consider new shaft seals. When I changed mine, they were loose in the casting and had no appreciable grip on the shaft. While cdnlouie's comment is correct regarding outside air pressure working to seal the lip in use, that's not to say they wouldn't be capable of stopping a trickling of fuel with the engine off.

He once advocated changing them out and suggested many Visions would benefit from the new seals. Perhaps he just objects to my conclusion that leaking fuel past the (static) seal was indicative of a bad seal? Even if my conclusion is wrong, I'd still think 30 year old rubber is no longer providing the seal that was intended. Just my 2 cents. Here's a discussion on the topic:
http://ridersofvision.net/rovforum/index.php?topic=6017.msg117298#msg117298

Mine are rigid, but not torn or dry-rotted. I think they're probably vacuum tight, but not water tight without any pressure. Dousing them with carb cleaner doesn't change the RPM's, so I think it's good enough to finish out the season on. I'll change them this winter for sure (there's probably only a week or two left before the lake-effect snow begins in South Bend), so that's not very long from now anyway.

[Rick G]

Replacing the shaft seals is a good idea, but don't go into the project unless you ready for the difficulty involved. The screws in the butterfly  are sacrificial and not available from YIC. Also realignment is not easy. Proceed with caution.