Carbs leaking @ thottle plate shaft - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
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post #1 of 6 (permalink) Old 11-15-2018, 04:55 PM Thread Starter
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Carbs leaking @ thottle plate shaft

As the title says. I discovered the leak while cleaning the carbs. I've been having lean issues about 1/4 throttle and think I've found the problem. After spraying the throttle plate with carb cleaner, I dried it with compressed air and had a lot of bubbles coming through the shaft on the outside.
I can't find the seals though. The exploded parts diagram does not show the shafts and plates removed and I can't get a part number. The yamaha dealer near me couldn't find any seals. I've been told to replace the carbs unfortunately. Is this true or do I have other options? I tried to pull one of the shafts to check out the seals, and getting the plate out unharmed seems like a bear.

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post #2 of 6 (permalink) Old 11-15-2018, 06:21 PM
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are you saying the carbs are blowing air OUT thru the butterfly plate shaft?

The carbs should never be under pressure, always under a vacuum when the bike is running.
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post #3 of 6 (permalink) Old 11-15-2018, 08:14 PM
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Think he meant that the carb cleaner was blowing out, when using the compressed air to dry it.
You shouldn't need ot use compressed air to dry it if your using carb cleaner.
Most I do is papertowel to cleanup any gas the carb cleaner ethonal crap.

Otherwise, I don't really understand what is bubbling.
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post #4 of 6 (permalink) Old 11-15-2018, 08:16 PM
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Carburetor throttle shafts do not have seals. They have a bushing normally of brass which is pressed in. There is always a small amount of air that enters thru the shaft bushing. It's not enough to matter, unless really, really worn. Any air entering does not affect anything, it's that small of an amount. Here an example.

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post #5 of 6 (permalink) Old 11-16-2018, 08:15 AM
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If there isn't any play at the shaft then there's nothing to be concerned about because, as lesblank mentioned, any air that might leak past the shaft during operation is minuscule at best. Incidentally I've never seen shafts worn badly enough to have play in them... even with carbs from junkyard bikes that had severe rust on all linkages.
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post #6 of 6 (permalink) Old 11-23-2018, 10:23 AM Thread Starter
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There is a decent amount of play in the shaft. I took the bushings out, they are plastic and shaped like a common crankshaft or fork seal. I could almost measure the gap between shaft and seal. How much is too much? It seems like a very large quantity of air passing. Practically foaming, not a couple micro bubbles. I can’t accelerate above quarter throttle without the choke. I have a thread about in the vstar forum. I was hoping I found my problem. Can I use orings to replace my seals? I haven’t leak checked the other one yet. I wonder if I should just buy a used set of carbs
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