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carb over flowing issue

Old 01-25-2017, 10:36 AM
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carb over flowing issue

Hi all... I just cleaned out the carbs from a super hawk thats been sitting a while. 15 years.. put it all together and it fired up... later that night i smelled gas in the garage.
notice gas leaking from carb, took carbs out again noticed gas had over flown and filled up cylinder... floats looked good, so i ordered new float valves... does this sound right to you guys? ... it has to be the valve sticking causing the float to stay open allowing all the gas to over flow and fill up the cylinder... I was able to suck up all the gas from the cylinder... please all advise welcome.
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Old 01-25-2017, 11:57 AM
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The other place to check is the vacuum petcock under the tank; these can also stick open allowing gravity to do it's thing. In conjunction with a float valve not sealing perfectly, that will lead to an overflow; I had exactly the experience that you describe. The petcock is a standard Honda design and you will be able to locate a rebuild kit for the diaphragm from K&L if not OEM.
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Old 01-25-2017, 02:15 PM
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Originally Posted by Cadbury64 View Post
The other place to check is the vacuum petcock under the tank; these can also stick open allowing gravity to do it's thing. In conjunction with a float valve not sealing perfectly, that will lead to an overflow; I had exactly the experience that you describe. The petcock is a standard Honda design and you will be able to locate a rebuild kit for the diaphragm from K&L if not OEM.
ok, how can I test that the diaphragm in the petcock is working properly..
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Old 01-25-2017, 03:05 PM
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Fuel should only flow to the carbs when there is a vacuum to the petcock. If you disconnect a fuel hose at one of the carbs and drain that to a bucket, and then draw a vacuum (your mouth is fine) on the thin vacuum tube plugged into the back of the petcock, fuel flow should start, and then stop when the vacuum is released (there may be a small time lag before it cuts off fully, a few handfuls of seconds). If fuel is flowing without vacuum, your petcock is stuck open.

The front of the petcock is square peg that operates a manual fuel tap. IIRc you turn this full clockwise half a turn with an 8mm spanner to shut it off (or it might be counterclockwise!).
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Old 01-25-2017, 03:35 PM
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Originally Posted by Cadbury64 View Post
Fuel should only flow to the carbs when there is a vacuum to the petcock. If you disconnect a fuel hose at one of the carbs and drain that to a bucket, and then draw a vacuum (your mouth is fine) on the thin vacuum tube plugged into the back of the petcock, fuel flow should start, and then stop when the vacuum is released (there may be a small time lag before it cuts off fully, a few handfuls of seconds). If fuel is flowing without vacuum, your petcock is stuck open.

The front of the petcock is square peg that operates a manual fuel tap. IIRc you turn this full clockwise half a turn with an 8mm spanner to shut it off (or it might be counterclockwise!).
ok... thank you.. My carbs are off right now... So I should be able to turn the fuel valve on and have no gas coming out of the petcock... ..


also.. just tested my float needles, the one shuts the gas off when the float goes up, the other keeps leaking gas... I will test out the petcock later tonight when I get home... I believe I am on the right track?
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Old 01-25-2017, 06:41 PM
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Originally Posted by tradaroo View Post
ok... thank you.. My carbs are off right now... So I should be able to turn the fuel valve on and have no gas coming out of the petcock... ..


also.. just tested my float needles, the one shuts the gas off when the float goes up, the other keeps leaking gas... I will test out the petcock later tonight when I get home... I believe I am on the right track?
Sounds about right:
No fuel will flow with the manual tap turned off
No fuel should flow with the manual tap open and no vacuum applied
Fuel should flow with the manual tap open and vacuum applied

Fuel should only overflow from the parked bike if the vacuum petcock and at least one float valve are faulty.

On my bike, I rebuilt the petcock but did not open the carbs, and my leak stopped.
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Old 01-25-2017, 08:18 PM
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Originally Posted by Cadbury64 View Post
Sounds about right:
No fuel will flow with the manual tap turned off
No fuel should flow with the manual tap open and no vacuum applied
Fuel should flow with the manual tap open and vacuum applied

Fuel should only overflow from the parked bike if the vacuum petcock and at least one float valve are faulty.

On my bike, I rebuilt the petcock but did not open the carbs, and my leak stopped.
Thank you very much for the help
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Old 01-25-2017, 09:27 PM
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You said you got new float valves? That is key since the old rubber on old ones will tend to not seal. Even if they look good.

You can rebuild or replace the petcock if bad.
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Old 01-25-2017, 09:45 PM
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Originally Posted by smokinjoe73 View Post
You said you got new float valves? That is key since the old rubber on old ones will tend to not seal. Even if they look good.

You can rebuild or replace the petcock if bad.
Excellent .. thank you... Just ordered the new float valves today....
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Old 01-27-2017, 05:53 AM
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as said make sure to check that petcock because fuel shouldnt be getting to the carbs in the first place without the engine running
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Old 01-27-2017, 09:04 AM
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Originally Posted by fabiostar View Post
as said make sure to check that petcock because fuel shouldnt be getting to the carbs in the first place without the engine running
I did check the petcock... It is constantly releasing fuel? the rubber on the diaphragm looks good? i ordered a new rebuild kit today...
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