Topic: in line fuel filters and fuel flow problems

[paulages]

i've had this problem on other bikes, but i always associated it with poor routing of the lines between the petcock and the carbs.

fuel flows freely from the petcock with no lines attached. attach the lines and it won't flow past the filter. yes, they are oriented in the correct flow direction. it seems as if there is too much air in the lines, and it can't properly vent so that the fual can get past the air in the line.

anybody have this problem? solution?

[BobbyR]

Check your venting.

[ProTeal55]

I agree.
Sometimes I have had the same issues when using in-line fuel filters.
They seem to be more of a headace then it's worth, so I just rely on the
petcock screen to filter the junk..

[crazypj]

Did you shorten the lines to take into account the extra length with filters? I had to make lines longer than stock to get a nice sweep, they would kink otherwise.
I guess you mean the filters have flow direction arrows with arrow pointing towards carb? If they are lying sidewayys you will always have some air in them. Try longer lines, looping under manifolds with filters upright.
PJ

[paulages]

yes, i shortened the lines a bit. the line going to cyl. 1 and 2 is using a 90deg. filter which works perfect straight out of the petcock. it's the other filter, going to 3 and 4 that's a problem, and it's is indeed on it's side. i don't think i can route it any other way. i'd love to rely on my petcock screen if it was intact. 

not certain that the tank vent is free, but the other side flows fine, and i tried taking the cap off altogether just to eliminate that possibilty. the usual "flick the filter until it starts flowing" method just won't work for some reason. the fuel just stops at the filter.

[heffay]

is this with the bike running?  the vaccumm of the running pressure may not let that problem matter.

if it is running then, j/k... i was testing you 

[grumburg]

Had the same problem until I found the filters were higher than the bottom of the petcock. One of the 3 things you need to know to be a plumber is s**t doesn't run uphill.

[paulages]

Had the same problem until I found the filters were higher than the bottom of the petcock. One of the 3 things you need to know to be a plumber is s**t doesn't run uphill.

yeah, i've sorted out the same problem for other people before. i've also had a problem when the line dips down below them carb inlet, even if the entire line is below the petcock. in this case, it is a clear run (lateral, but then) downward.

[Kevin D]

One of the 3 things you need to know to be a plumber is s**t doesn't run uphill

LOL    Okay grumburg, lots of folks here in Michigan looking for a new career - not me yet - so what are the other 2?

Will you take an apprentice if he knows one of the three?


I tried and got rid of the filters for the same reasons. The gas tank crap has several chances to settle before it plugs things up - in

the tank, in the petcock, in the floatbowls. I clean them all once a year and get the least little junk out. And I try to stay off reserve.

[BobbyR]

Actually you may want to check the petcock filter, it may be plugged up not delivering a lot of gas to the filter. I know you said it flows freely, but that sounds subjective.

[paulages]

i will certainly check again, but when the fuel line is removed, it pours fuel all over my new-paint-job protecting rag. i thought it was clogged the first time, so i dumped the fuel, sloshed it around some more, and reinstalled the petcock. this time, it's only seen the "on" position, so it shouldn't clog.

[ProTeal55]

"Reserve" is a bad thing.
Always collects all the crud at the bottom of the tank.
I am anal when it comes to gas, so I always top off my tank every few days anyways.

[grumburg]

One of the 3 things you need to know to be a plumber is s**t doesn't run uphill

LOL    Okay grumburg, lots of folks here in Michigan looking for a new career - not me yet - so what are the other 2?

Will you take an apprentice if he knows one of the three?


I tried and got rid of the filters for the same reasons. The gas tank crap has several chances to settle before it plugs things up - in
Hot's on the left and don't chew your fingernails.
the tank, in the petcock, in the floatbowls. I clean them all once a year and get the least little junk out. And I try to stay off reserve.

[grumburg]

Hot's on the left and learn not to bite your nails.

[wheelie]

I had a similar fuel flo problem recently and traced it back to the inline fliter scraping the inside of the fuel line during install and wadding up a little bit of rubber ahead of it. Try pulling out that section of hose completely and blow through it to see if plugged.

[jdpas29]

make sure your filter is turned the right way if it doesn't have arrows.  blow through it to see which side has more of a restriction.  the side that blows easier is the side that the fuel should be going through first.

[petercb750]

Speaking of fuel line - does anybody know where I can get some of the original type fuel line as fitted to K2 750's?? All I can get here is the modern thick-walled type, but I would like to get hold of some of the thin black tubing - DSS tell me it is discontinued (due to modern spec requirements maybe??).
The modern stuff fits ok (ie internal diameter is ok) but looks a bit fat and chunky on the bike.
Cheers
Peter.

[theunrulychef]

This should fix your fuel problems  .

Back to the topic.  I probably shouldn't even ask this, but these are new fuel filters, right?  I'm just saying because if you used your old ones from before you started your build, they might have a decent chance of being gummed up inside.

Have you tried pulling the tank off & running fuel through your lines & filters - dangling straight down?  You could pull off each piece in the chain until fuel starts flowing, then you could find where your blockage is - if that is indeed the problem.

On my neighbor's 550, he actually had a kink in the line that he couldn't see because of the way the line was routed.  I gave him some new line & it fixed the problem.  Sounds like you already checked for that though.

Hope you get her running right soon.
Good luck,
Jay in Philly

[Chris Liston]

I'd pay $500 for those if they had them or the 550 just because the look so damn cool

[byidesign]

If you have a NAPA store, go into
     the small engine section{lawnmowers  ,grasstrimmers,outboards etc.}
     they have a little "pancake" white in colour @ 1 1/4 dia. 1/2 wide. inline
      filter,{screen type, and cleanable} that adjusts anywhere
       from straight to 90 degrees.{opens to clean with a pocketknife
           flatblade} good if you are on the road....
         I now have one one all of my bikes, and have found
         you can make it fit almost anywhere..
            no noticeable flow restriction, until it
          starts to clog up. Has saved me some headache's.
             for sure...
             Hope it helps
                     Bruce

[paulages]

well, it's working now, though there is still a massive air bubble from the point where the fuel line pokes through the front of the carb assembly (in other words an inch or two from the fuel inlet) all the way to the outlet end of the fuel filter. apparently it's allowing fuel to flow by, though i can't seem to witness it even while running it at high RPM. i do suspect fuel starvation still though. WOT is lagging just a bit, which i would expect with pods, a homemade glasspack and wild-guessed mains in the carbs. i know i still need to do my plug chops and sort them out, but i'm pretty certain it wasn't doing it when i first rode it. slow fuel flow could be starving the mains.

i've used these filters on every 70's honda i've had (many), and believe me---making sure i wasn't just being an idiot with the filter turned backwards was the first thing i checked.