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Join Date: Nov 2009
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Filter over a fuel cock in two wheeler

11/20/2009 10:19 PM

In my motorcycle, recently I fitted an inline fuel filter between the petrol tank and the carb. I get fuel starvation problem very often. I need to remove the fuel hose and refit it. It becomes okay for sometime. Again the problem repeats. What could be the technical reason and what should I do. Replacing a filter is one solution. Without online filter there is no problem.

saran

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#1

Re: Filter over a fuel cock in two wheeler

11/21/2009 12:52 AM

Hello, Most motorcycles fuel systems are gravity fed. If the filter is to restrictive to free flow the carbs will run out of fuel faster than it's being replaced. For a fuel filter just a fine mesh filter is all you need to keep any junk out of the carb that's big enough to block any fuel passage.

Also on some bikes they will use a vacum line to cause fuel to flow in the run position of the fuel valve. On these bikes the only time fuel will flow is when turned to prime position.

Last if the fuel tank is lower than the carbs/injectors then it has to have a fuel pump.

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#2

Re: Filter over a fuel cock in two wheeler

11/21/2009 10:59 AM

metalSmiths is right.

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Member

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#3

Re: Filter over a fuel cock in two wheeler

11/21/2009 11:31 PM

The filter is too small, installed backwards, higher than the fuel pump, if you have a diaphram pump, a plug or a leak will mess you up. Rust in the tank, water in the float bowl will give the same symptoms. The most embarrassing is "no gas in the tank".

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#4

Re: Filter over a fuel cock in two wheeler

11/22/2009 12:24 PM

Why not check the most obvious cause a blocked vent hole in the fuel cap or elsewhere on the tank.Lack of a vent in a gravity fed system will vacuum lock causing starvation.

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#5
In reply to #4

Re: Filter over a fuel cock in two wheeler

11/22/2009 3:24 PM

Reread OP's question. No filter no problem.

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#6

Re: Filter over a fuel cock in two wheeler

11/23/2009 12:54 AM

Finally, I put a small 0.5mm hole on the filter and became okay. lastthree days absolutely no problem. But similar vehicle of my friend runs without a small hole on the filter. I think tis something to do with the constructio of the filter and the mesh sizes. Th filter whatI am talking a simple one. The petrol if gravity fed. It is below the fuel tank. Breathr in cap is okay. The hole madeon the filter had solved the problem. But technically I could not fnd answer why n some it is working and in others it is not so. But i the market there are filters available with or without vent hole.

I am yet to get the correct technical reason. However my problem got solved. Thank you all for the input.

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#7
In reply to #6

Re: Filter over a fuel cock in two wheeler

11/23/2009 2:50 PM

It is not unusual for trash in the fuel tank to coat the filter screen causing fuel starvation. Pulling off the hose and blowing in it or sometimes, just banging on the tank will often loosen the debris on the fuel cock strainer and allow the engine to get sufficient fuel for a while. Eventually, the screen plugs up again and the procedure has to be repeated. The best thing to do is to remove the fuel cock assembly and wash out the tank with a little fuel. If rust is the problem, there are coatings available that will cover the rust and keep it from fouling the filter screen.

Making holes in the screen just allows the trash to flow down the line and get into the carburetor leading to ruin there. If the trash problem is so severe that you have to defeat the filter at the fuel cock, be certain to put a larger capacity filter in the fuel line before the carburetor to keep the trash from fouling up your expensive carburetor(s).

I have seen this happen on new motorcycles where tiny beads of welding spatter were left in the tank from fabrication. Washing out the tank with a little fuel and cleaning the fuel cock strainers is all that was required to put those right.

Another thing that can happen is vapor lock. If the fuel starts to vaporize in the added fuel filter, it can block the flow of fuel from the tank. This will cause the engine to stall or to run lean. Pulling off the hose, can break the vapor lock bubble and allow the fuel to flow again. This is also not uncommon for added fuel strainers as they are typically in the hot air stream behind the cylinders. This would seem to not be the case though if piercing the fuel cock strainer resolved the issue.

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Member

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#8
In reply to #7

Re: Filter over a fuel cock in two wheeler

11/23/2009 11:35 PM

Thank you for the good information.

I can see a holistic picture of adding an external flter.

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Users who posted comments:

Agile (1); Anonymous Poster (1); greypoopon (1); lyn (1); metalSmiths (1); Saranathan (2); Turbotroll3 (1)

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