Air in fuel line and backfiring help needed. - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

 
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post #1 of 9 Old 03-23-2009, 06:31 PM Thread Starter
 
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Air in fuel line and backfiring help needed.

I have a clear fuel line and noticed that an air gap of about 2-3 inches develops in the fuel line from the petcock down. I originally thought it was the vacuum, so I bypassed the vacuum system so it's just an on/off petcock. With the fuel hose removed and the petcock turned on, things flow very well and without stop. I have bled the air gap out and it will return after riding for a while. I wasn't too worried about it until the bike started running poorly today. I switched to reserve and it seemed fine. So I rode to the gas station to fill up and was only down maybe 2 gallons. Once filled, it ran fine, but the air gap is back. What's a guy to do? Thanks for any and all advice in advance.

One last thing, it seems to be backfiring a lot more on deceleration too.
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post #2 of 9 Old 03-23-2009, 06:42 PM
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Open the gas cap to see if you are having venting problems.

Tim

2005 KLR 685
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2012 Yamaha Super Tenere; Purchased 7/30/2011; Sold 5/23/2015
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post #3 of 9 Old 03-23-2009, 06:53 PM Thread Starter
 
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Originally Posted by tomatocity View Post
Open the gas cap to see if you are having venting problems.
Thanks for the response. I tried that. The thing that has me stumped is that when the fuel hose is removed, the gas flows perfectly as long as I keep the valve open.
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post #4 of 9 Old 03-23-2009, 07:19 PM
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If it was running OK before your changes, put it back like it was.
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post #5 of 9 Old 03-23-2009, 07:41 PM Thread Starter
 
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If it was running OK before your changes, put it back like it was.
Thanks. It's been running fine for 500+ miles since the change to the petcock. I do have a few other petcocks I could use from other bikes. Maybe I will try that if it keeps giving me problems.
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post #6 of 9 Old 03-23-2009, 08:59 PM
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The vacuum hose can easily get bent/crimped and limit the amount of vacuum. Get a longer piece of vacuum hose and route it over the top of the caburetor and to the petcock. This will prevent the vacuum hose from being bent/crimped.

Tim

2005 KLR 685
2015 Yamaha Super Tenere ES, 5/23/2015
2012 Yamaha Super Tenere; Purchased 7/30/2011; Sold 5/23/2015
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post #7 of 9 Old 03-23-2009, 09:10 PM Thread Starter
 
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Originally Posted by tomatocity View Post
The vacuum hose can easily get bent/crimped and limit the amount of vacuum. Get a longer piece of vacuum hose and route it over the top of the caburetor and to the petcock. This will prevent the vacuum hose from being bent/crimped.

Thanks for the advice, but I have the vacuum line removed and capped. I also have the diaphragm removed in the petcock with a seal kit. It did the same air in the line when the diaphragm was installed. I have also put a new diaphragm in the carb. It's very strange indeed.
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post #8 of 9 Old 03-23-2009, 09:43 PM
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I know this is a reach, but could the clear line you installed be degassing? Put another way is the tubing approved for petrolum based products? Could be deteriorating the line and resulting in plastic in the fuel, and other gasses being released. A sign of this would be the line becoming discolored. Other then that I got nothing. LOL

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post #9 of 9 Old 03-23-2009, 10:25 PM Thread Starter
 
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I know this is a reach, but could the clear line you installed be degassing? Put another way is the tubing approved for petrolum based products? Could be deteriorating the line and resulting in plastic in the fuel, and other gasses being released. A sign of this would be the line becoming discolored. Other then that I got nothing. LOL
Thanks again for the advice. I am actually using clear fuel line for motorcycles. I bleed off the excess air and it comes back within a few minutes of riding. Really strange. It's almost like air bubbles are coming from the carb up through the fuel line?? Could there possibly be a correlation between the backfiring and the air getting in the system. I seem to recall an anti-backfiring diaphragm on the side of the carb. Maybe that has a pin hole and is somehow causing the air feedback?
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