XR400 Fuel Line - Sizing and filter questions...

A couple questions...

  1. Will it hurt to go from factory size of 5/16" diameter hose to 1/4" hose?  The reason I ask is because there are many, many more filter options available in the 1/4" diameter size.
  2. Is an in-line fuel filter really even needed???  I ask this because when I pulled the petcock out...it is made of a very fine screen-like material and I there is no way ANYTHING  is getting past it.  Putting an inline filter a couple inches away from the petcock seems repetitious and unnecessary.  Am I missing something here?

If the pet cock screen is intact I don't see a point in a fuel filter. As for the fuel line size the microfiche indicates the fuel line size to be 7.5 mm so neither 5/16 or 1/4 inch is correct but as long as you clamp them you can make either work.

i run inline filters also just because inspecting the petcock screen requires an empty tank on mine i like having the redundancy and I think the micron rating of the inline is greater than the in tank screen

I have gotten peace of mind with the brass insert VisuFilters for over forty years.  I have had the petcock screens disintegrate recently and some say it is the ethanol gas. The $3 or $4 bucks is money well spent to me. Good luck.

thats the filters I use and also  my fear

  the screen failing

+1 on the previous posts.  The tank filters are difficult to inspect and are plastic that can deteriate. So I run transparent inline filters.


My experience with the funny hose sizes that Honda uses is to buy OEM, or a premium aftermarket motorcycle hose.


The premium hoses such as Motion Pro Premium have enough stretch that you can use 1/4" but on a 400 better to use 5/16" with clamps.  I've found OEM spring wire clamps OK.

I totally agree with the oem hose.  The material composition is superior and it's even formed to fit the bike.  For my bike it is also sheathed.  Renew it when it's no longer soft and supple. 


My friend has stuff going into his XR4 carb every time he pulls the tank.  My solution is to plug the end of the fuel line with a bolt so dirt cannot enter the hose when you disconnect it.  It only takes one piece of grit to plug your pilot jet. 


I doubt ethanol would attack the plastic screen but gasoline sure would after many years.  There could be ethanol gum forming after the screen, though.

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