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Thread: Fuel filter ? 78' R100/7

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    Registered User godfather's Avatar
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    Fuel filter ? 78' R100/7

    Will a bad fuel filter stop gas from flowing into the filter?

    Here is the deal. New filters and lines installed after tank was flushed and screens cleaned.
    Put about 80 miles on the bike...stalls. Fuel filters dry. Thought I ran out of gas, no, still about 1.5 gal. I blew into the fuel lines to clear any sediment I may have missed that could have clogged the screens. Ride about 2 miles, same thing. I clear lines again and make it home.
    Now home, gas tank removed and drained, fuel taps removed. and flushed tank with gas, then washed, rinsed clean, completely dried with a fan/hose blowing air into the tank for days. Reassemble everything, put new gas in tank, open taps...no fill to the filters. I disassemble left fuel tap, its clean, disc is perfect, pliable, o-ring is great. Tap reassembled, turn on both taps again, no flow into the filters. I remove gas cap, still same result. I can blow air through the filters, but it takes more than a gentle puff of air to get it to flow. I get gas flowing from both taps with filters removed. Lines are clear to the T's as is the L/R connector line. Lines from the T's to the carbs are clear plastic lines and clean.

    I am puzzled as to why the gas will not even flow into the filter. Is it the fact that the fuel is gravity fed and not pumped? I cannot see any sediment or junk in the filters. Could they have been plugged by such fine particles that the blockage is not visible?

    Can anyone shed a little light on this? Here is the DUMB question part of the post... just to be sure...the arrow on the filter is the flow direction, correct

    Any way, I am picking up new filters tomorrow and will try them when I get home.

    BTW both Carb bowls are clean
    TYIA
    Attitude is everything!
    1978 R100/7
    08' V-Strom 650 great light weight tourer

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    Quote Originally Posted by godfather View Post
    Will a bad fuel filter stop gas from flowing into the filter?



    Can anyone shed a little light on this? Here is the DUMB question part of the post... just to be sure...the arrow on the filter is the flow direction, correct
    You are correct on the arrow indicating the direction of flow.

    I would add that 1.5 gallons is the approximate amount of fuel left when you switch to "reserve".

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    Do you get flow from the tank when the fuel lines are removed? I mean, just down to and through the petcocks?

    If you do, then reconnect the fuel lines to petcocks, and disconnect from carbs. Do you get fuel flow then?

    If not, then probably fuel filters. I am assuming you are using the in-line filters sold at places like Max's and other places.

    Even then, they are cheap. Replace them.

    Also, check with gas cap removed. This normally does not happen quickly, but if the tank vent is stopped, it can't get air, and can't let fuel flow. This doesn't usually happen fast, but only after there becomes a vacuum in the tank enough to overcome the weight of the fuel trying to flow out.

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    Registered User godfather's Avatar
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    Quote Originally Posted by jimmylee View Post
    do you get flow from the tank when the fuel lines are removed? I mean, just down to and through the petcocks? yes

    if you do, then reconnect the fuel lines to petcocks, and disconnect from carbs. Do you get fuel flow then?noi

    if not, then probably fuel filters. I am assuming you are using the in-line filters sold at places like max's and other places.correct

    even then, they are cheap. Replace them. picking them up at lunch time

    also, check with gas cap removed. tried that, no difference this normally does not happen quickly, but if the tank vent is stopped, it can't get air, and can't let fuel flow. This doesn't usually happen fast, but only after there becomes a vacuum in the tank enough to overcome the weight of the fuel trying to flow out.
    i also forgot to mention the overflow/vent line is clear.
    I will post after new filters are installed.
    Attitude is everything!
    1978 R100/7
    08' V-Strom 650 great light weight tourer

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    Registered User toooldtocare's Avatar
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    I assume you also took the screens out of the tank. If you just remove the fuel petcocks, sometimes the screens stay trapped in the tank. I use a safety pin that is bent 90 degrees at the end to pull them out.

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    Registered User godfather's Avatar
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    Quote Originally Posted by toooldtocare View Post
    I assume you also took the screens out of the tank. If you just remove the fuel petcocks, sometimes the screens stay trapped in the tank. I use a safety pin that is bent 90 degrees at the end to pull them out.

    Yes, the screens were removed and cleaned as well.
    Attitude is everything!
    1978 R100/7
    08' V-Strom 650 great light weight tourer

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    Registered User lmo1131's Avatar
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    ... just for sh*ts'n'giggles, if fuel passes through the petcocks, try by-passing the filter(s) altogether.

    from your first post it sounds like everything was working properly (if you got 80 miles down the road).
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

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    Registered User godfather's Avatar
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    Tonights report

    I replaced the fuel filters with new ones and the fuel lines with ethanol proof non FI type line. The bike fired right up . I kept the idle up around 1300 and watched the filters. They had gas flowing through them. I noticed the gas line from the T to the right carb had a large air bubble in it only to discover it was split and sucking in air. I removed that clear (say yellowed) piece and replaced both sides with the new black line. Fired it up again, no leaks. I ran the rpm up to 3000 for about 30 seconds, then down to 1500 for 15 seconds then back to 3000 and watched the filters. Both sides maintained about 1/3 full of gas.

    I thought they were suppose to fill with gas, but apparently not...is this right?

    It has been and will continue to rain hard for the next couple days, so no test ride until hopefully Saturday afternoon.
    Attitude is everything!
    1978 R100/7
    08' V-Strom 650 great light weight tourer

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    Quote Originally Posted by godfather View Post
    Tonights report

    I replaced the fuel filters with new ones and the fuel lines with ethanol proof non FI type line. The bike fired right up . I kept the idle up around 1300 and watched the filters. They had gas flowing through them. I noticed the gas line from the T to the right carb had a large air bubble in it only to discover it was split and sucking in air. I removed that clear (say yellowed) piece and replaced both sides with the new black line. Fired it up again, no leaks. I ran the rpm up to 3000 for about 30 seconds, then down to 1500 for 15 seconds then back to 3000 and watched the filters. Both sides maintained about 1/3 full of gas.

    I thought they were suppose to fill with gas, but apparently not...is this right?

    It has been and will continue to rain hard for the next couple days, so no test ride until hopefully Saturday afternoon.
    If I remember correctly, mine also have air bubbles that stay there. The only thing I can think to make sure of is the flow arrow should point down toward the carbs to match the flow of fuel through the filter.

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    I think my filters have sintered bronze and over time, I am sure they can get clogged up with crud as much as any other filter.

    I think there are also some that have a paper-type corrugated element inside as well. Ditto on those too - I am sure they can get clogged up as well.

  11. #11
    #4869 DennisDarrow's Avatar
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    I use the clear plastic with the arrow that you refer to on your bike. I usually only turn on the left side petcock until that side is empty and then turn on the other till reserve. If I fail to fill up and don't remember when I get home, the next time I start the bike, I turn on the left, look at the filter that is empty, and it reminds me that I need to get some fuel and start on reserve. So, YES, the filter, when you have gas, should have fuel evident in it.
    As to being full, that depends on perhaps how hard one is running?......For me, It is only empty when I am out of fuel. Hmmmmmm on my wood chipper, that uses the same type of filter, it only shows a trickle going into/out of the filter; but my splitter shows full all the time unless out of fuel. lol.........WHO knows, if it runs....ride it........God bless.......Dennis

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    Monza Blue 1974 R90/6
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    From time to time, I use the in line filters that Bing sells. They are always full of gas when the petcocks are open. No air. Definitely not 1/3. Maybe it has something to do with the routing of your lines and you could post a picture for all to study and comment on?

    Also, big debate not far back about whether you even need those in line filters. They have the capability to cause at least as many problems as they are intended to prevent.

    Barron

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    Registered User godfather's Avatar
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    Quote Originally Posted by barron_williams View Post
    From time to time, I use the in line filters that Bing sells. They are always full of gas when the petcocks are open. No air. Definitely not 1/3. Maybe it has something to do with the routing of your lines and you could post a picture for all to study and comment on?

    Also, big debate not far back about whether you even need those in line filters. They have the capability to cause at least as many problems as they are intended to prevent.

    Barron
    Here you go...

    Attitude is everything!
    1978 R100/7
    08' V-Strom 650 great light weight tourer

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    Quote Originally Posted by barron_williams View Post
    From time to time, I use the in line filters that Bing sells. They are always full of gas when the petcocks are open. No air. Definitely not 1/3. Maybe it has something to do with the routing of your lines and you could post a picture for all to study and comment on?

    Also, big debate not far back about whether you even need those in line filters. They have the capability to cause at least as many problems as they are intended to prevent.

    Barron
    I can't see how they could be a problem unless they restrict flow that carbs need. I've had mine on now this whole past spring and summer, 9,000 miles without 1 problem that I know of. Mine were the smaller ones sold by Max's BMW, about $2 each.

    What problems could they cause?

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