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Old 02-22-2011, 09:38 AM
Jeminyar's Avatar
Jeminyar Jeminyar is offline
Join Date: Feb 2011
Location: Phoenix, Arizona
Posts: 6
Newb carb and petcock help

Hi All!
I'm new here, just purchased my very first motorcycle two weeks ago. A 1981 XS1100H, not running and not pretty but was $600. Also I believed it was only be a new battery and carb cleaning away from running like a champ. Well after cleaning the carbs and petcocks and reassembling and installing it all back onto the bike (with new pod filters btw) I couldn't get it start. Here's the lowdown of the things I've checked out:
1. I noticed quite a bit of gas coming from the two carbs on the Right side. I took off the pod filters and saw a steady stream of gas coming from them (see picture below).
2. I moved the petcock valve from the ON position to the PRI position and the gas slowed then stopped.
3. I moved the petcock valve to the RES position and no new gas appeared.
4. Tried starting in bike in both PRI and RES positions but was not successfull.
5. Then realized I had not hooked up throttle cable when I reassembled everthing (dummy!).
6. Disconnected the fuel lines and vacuum lines from petcocks and pulled the gas tank.
7. Then with the tank (with attached petcocks) pulled off the bike I moved the petcock valve from the RES positions to the ON position. Gas poured out of the petcock. (I thought that wasn't supposed to happen when the bike is not running?)
8. Turned the petcock valve back to PRI and RES positions and gas did not flow in either position.

Any ideas???? Here's the pic of the gas flowing from Carb 3:


Last edited by Jeminyar; 02-22-2011 at 09:39 AM. Reason: Adding different picture
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Old 02-22-2011, 09:59 AM
crazy steve crazy steve is offline
Join Date: Jan 2009
Location: Beautiful outer Yelm, WA
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You've got two separate things going on... one, the petcocks aren't working right. And two, the float valve in the carb(s) are leaking.

It almost sound like the petcocks may be mis-assembled; you didn't mix parts between the left and right sides did you (they are different)? You should get fuel flow on PRI, but none on RES or ON with the engine stopped.

And the carbs, that looks like a pretty typical leaking float valve. The '80-81 carbs have an o-ring that seals the float valve needle seat, and those go bad.

You can get rebuild kits for both the petcocks and carbs from eBay seller 'Georgefix'. If you just disassembled/cleaned what you had, disturbing the old seals/gaskets can do this...
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Old 02-22-2011, 10:55 AM
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XSive_speed XSive_speed is offline
Join Date: Nov 2010
Location: Cedar Rapids, IA
Posts: 45
+1 on the diagnosis. The float valve is not closing off and the petcock is leaking. I'm getting ready to open up my petcocks too for a cleaning due to a small leak, so I have to trust what Steve said about them being different internally. I'm wondering if you swapped the cover plates so that prime and reserve are reversed. That would explain fule flowing in reserve and stopping in prime.

In reguard to the carb float valve - looking at the volume of gas pooring out in the pic, I'm wondering if your float may be hung up wide open. Did you try tapping around the bowl to free a stuck float? If so, you probably need to open up the leaking carb again and re-check your assembly. Also check the condition of the o-ring under the float valve seat. It would not cause the volume of gas you are seeing, but a good check while you have it torn apart.
John (XSive_Speed)

'80 XS1100G Standard
- 4 - 1 exhaust (probably Mac)
- UNI air filter
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Old 02-22-2011, 11:13 AM
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natemoen natemoen is offline
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Location: Fargo
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Agreed with steves diagnosis.

Another thought, if you still have the stock jets in the carbs most likely when you get her running you will be running pretty lean due to the pods you put on. Your getting a lot more air through the carbs but not any extra gas to compensate for it. So be prepared to up the main jets a couple sizes.

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Old 02-22-2011, 11:20 AM
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Jeminyar Jeminyar is offline
Join Date: Feb 2011
Location: Phoenix, Arizona
Posts: 6
Thanks for the help, I really appreciate it! I'll tear it all down again and check for the two things you mentioned....
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carburetor, petcock

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