Air In Fuel Line - Motorcycle-Journal Forums

hal9000 · 06-28-2007, 08:56 PM

Yet another question for you guys... and yet again thank you for all your help.

I recently noticed air in the fuel filter on more then one occassion on my 81 yamaha 400 special 2. The guy that I bought it from said he recently replaced the fuel filter, so im not really sure what kind of quality the filter is, but it is placed between the petcock and the carbs between some tubing. Its made of clear plastic and you can see a copper colored cone shaped filter in it. This is where Ive noticed the air collecting. So here are some questions:

Im pretty sure this is not good but should there be air in the fuel line?

The filter is placed so that it is horizontal. The fuel line is in an L shape between the petcock and the carbs, and the filter is on the horizontal leg of the L. Would it be better to remove more tubing so that the filter is more virtical so that the air would not collect in the filter but rather flow up throught the petcock?

Ive also noticed that the previous owner did not put the circular clamps where the filter is plugged into the tubing that ive seen else where on my bike. Is this where the air is getting in the fuel line? I can always buy some circular tighting clamp things ( i hope you know what im talking about.)

What kind of fuel filter is of good quality for my application?

Is there any other thing that could be causing air to get into the fuel line? And do you have any other solutions?

I think this is causing a lot of hickups at idle. If pics would help let me know.
Thanks for the help.

Easy Rider · 06-28-2007, 09:40 PM

Quote:

Originally Posted by hal9000

I recently noticed air in the fuel filter on more then one occassion on my 81 yamaha 400 special 2.
Im pretty sure this is not good but should there be air in the fuel line?

You worry too much.

Perfectly normal. If it bothers you, wrap some duct tape around it (so you can't see it).

Quote:

I think this is causing a lot of hickups at idle. If pics would help let me know.
Thanks for the help.

No, I don't think that little air bubble in the filter has anything to do with how it runs. Trust me, it just doesn't.

As long as the fuel line hose is in good shape, you don't need clamps. The filter is sized so that there is a tight fit and there is almost ZERO pressure in that line.

GregR1 · 06-28-2007, 10:22 PM

if you're worried about a lack of clamps, use those plastic zip-ties. you know, the long strip of plastic with a square hole at one end, you make a loop, pull the tip through the hole as tight as you want, and it locks in place. cheap, strong, rustproof, and handy.

hal9000 · 06-28-2007, 11:45 PM

I wouldnt worry if it was just a few bubbles... but the fuel filter fills 1/4 of the way up with air, which i thought was way to much

Easy Rider · 06-29-2007, 07:53 PM

Quote:

Originally Posted by hal9000

I wouldnt worry if it was just a few bubbles... but the fuel filter fills 1/4 of the way up with air, which i thought was way to much

Repeat after me:
THIS IS NORMAL. IT IS NOT A PROBLEM.

As the fuel goes down, some air comes UP.
Unless the filter is perfectly vertical (which it can never be on a bike), some of the air gets trapped in the filter.
It will NOT be a problem, even if as much as 1/2 is filled with air.

Now, moving right along...........

palanon · 06-29-2007, 08:13 PM

Yup, this is normal. If you feel it's close to vapor lock , tip the filter up and flick it with your finger ( fuel selector on ).

Bubbles be normal. Hose half filled with air - not normal.

Aussie Steve · 07-02-2007, 04:28 AM

Quote:

Originally Posted by Easy Rider

Repeat after me:
THIS IS NORMAL. IT IS NOT A PROBLEM.

As the fuel goes down, some air comes UP.
Unless the filter is perfectly vertical (which it can never be on a bike), some of the air gets trapped in the filter.
It will NOT be a problem, even if as much as 1/2 is filled with air.

Now, moving right along...........

Don't believe him

take it to a dealer who will charge like a wounded bull to tell you the same thing!!!!! Hahahahahahahahha

nuckles25 · 07-02-2007, 05:17 PM

THIS IS COMPLETELY NORMAL!! My FZ has more air in the fuel filter than gas just about all the time. Although my filter has two compartments, one of those compartments is so small that I could hardly tell it was there. That is the compartment that shouldn't have air in it because after this its straight to the carb.

06-28-2007, 08:56 PM	#1 (permalink)
hal9000 Newbie Joined: May 2007 Posts: 14	Air In Fuel Line Yet another question for you guys... and yet again thank you for all your help. I recently noticed air in the fuel filter on more then one occassion on my 81 yamaha 400 special 2. The guy that I bought it from said he recently replaced the fuel filter, so im not really sure what kind of quality the filter is, but it is placed between the petcock and the carbs between some tubing. Its made of clear plastic and you can see a copper colored cone shaped filter in it. This is where Ive noticed the air collecting. So here are some questions: Im pretty sure this is not good but should there be air in the fuel line? The filter is placed so that it is horizontal. The fuel line is in an L shape between the petcock and the carbs, and the filter is on the horizontal leg of the L. Would it be better to remove more tubing so that the filter is more virtical so that the air would not collect in the filter but rather flow up throught the petcock? Ive also noticed that the previous owner did not put the circular clamps where the filter is plugged into the tubing that ive seen else where on my bike. Is this where the air is getting in the fuel line? I can always buy some circular tighting clamp things ( i hope you know what im talking about.) What kind of fuel filter is of good quality for my application? Is there any other thing that could be causing air to get into the fuel line? And do you have any other solutions? I think this is causing a lot of hickups at idle. If pics would help let me know. Thanks for the help.

06-29-2007, 08:13 PM	#6 (permalink)
palanon No Significant Other Joined: Apr 2006 Bike: 2003 Bandit 1200S Location: Newmarket, NH Posts: 2,326	Yup, this is normal. If you feel it's close to vapor lock , tip the filter up and flick it with your finger ( fuel selector on ). Bubbles be normal. Hose half filled with air - not normal. __________________ " In the name of the Speedo, the Tach and the Holy Throttle, amen. "

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06-28-2007, 10:22 PM	#3 (permalink)
GregR1 ... Joined: Mar 2007 Posts: 2,308	if you're worried about a lack of clamps, use those plastic zip-ties. you know, the long strip of plastic with a square hole at one end, you make a loop, pull the tip through the hole as tight as you want, and it locks in place. cheap, strong, rustproof, and handy.

06-28-2007, 11:45 PM	#4 (permalink)
hal9000 Newbie Joined: May 2007 Posts: 14	I wouldnt worry if it was just a few bubbles... but the fuel filter fills 1/4 of the way up with air, which i thought was way to much

07-02-2007, 05:17 PM	#8 (permalink)
nuckles25 Where Am I ? Joined: Jun 2007 Bike: '87 Yamaha FZ700 Location: Milwaukee, WI Posts: 26	THIS IS COMPLETELY NORMAL!! My FZ has more air in the fuel filter than gas just about all the time. Although my filter has two compartments, one of those compartments is so small that I could hardly tell it was there. That is the compartment that shouldn't have air in it because after this its straight to the carb.

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