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Popping noise coming from exhaust and also..

Engine, Fuel and Exhaust

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Old Nov 9th, 2007, 07:50 PM     #1
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Popping noise coming from exhaust and also..

I'm getting popping(backfiring I'm assuming) coming from my exhaust and also what can only really be described as a "shuffing" noise coming what sounds like straight out of the air cleaner. Any ideas?


As always thanks in advance.


P.S.: I looked over some of the 'self-help' section and didn't really find it. Unless I saw it and didn't realize it.


UPDATE: I looked at my vacuum hoses under the tank and have a 'Y' shaped connector that only has two hoses attached. When I plug the missing one the engine runs much better. Anyone have an idea as to where I could find a diagram/schematic of the vacuum hoses on a Sportster '96?

Last edited by The Rook; Nov 9th, 2007 at 09:01 PM.
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Old Nov 9th, 2007, 09:32 PM     #2
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Re: Popping noise coming from exhaust and also..

The open vacuum linw will cause the popping you are experiencing.

Try to follow the two lines and see where they terminate and post what you find. Quite possible the missing line is from the intake manifold or the carb . You may find the third line you are missing disconnected.
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Old Nov 10th, 2007, 05:03 PM     #3
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Re: Popping noise coming from exhaust and also..

I looked at them again and one hose comes from above the carb another comes from a little circular thing(I'm researching it currently) and the third one is completely missing. I plugged the open port and took my motorcycle for a ride and that seems to have solved the problem with the popping noise. But I'm fearful that I still need that third vacuum hose hooked up to somewhere, and since I only have a Clymer manual I believe I'm totally screwed cause this Clymer manual is a total waste of money.
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Old Nov 10th, 2007, 06:52 PM     #4
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Re: Popping noise coming from exhaust and also..

The circular thing is probably the VOES switch that changes your cruise ignition advance. It has a vacuum line on it that goes to the carb. You may have a vacuum operated fuel petcock also, not sure on that bike but look on the back of the fuel petcock and see if there is a vacuum line on it. The other would probably come from the carb. If you are unsure the dealer can show you a diagram that would clear it up for you.

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Old Nov 11th, 2007, 11:06 AM     #5
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Re: Popping noise coming from exhaust and also..

Quote: Originally Posted by glider View Post
The circular thing is probably the VOES switch that changes your cruise ignition advance. It has a vacuum line on it that goes to the carb. You may have a vacuum operated fuel petcock also, not sure on that bike but look on the back of the fuel petcock and see if there is a vacuum line on it. The other would probably come from the carb. If you are unsure the dealer can show you a diagram that would clear it up for you.

I've encountered this same-thing on 2 bikes over the years both had replaced the ignition with aftermarket ignitions and felled to remove the VOES system completely and just plugged off the line going to the VOES switch. after a few heat cycles and the constant vibes the plug falls off and the bike runs like crap because of the lean mixture created by the open vacuum line.
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Old Nov 18th, 2007, 06:54 PM     #6
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Re: Popping noise coming from exhaust and also..

I will try to take photos later and see if I can post on here. Thank you for the replies.
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