Fuel Filter installation

There's only about 4" between the petcock on my cm450 and the carb
fuel intake. i bought a filter that's about 2" long and i'm having
trouble getting it to fit without kinking the line. am i correct in
assuming that since it's gravity fed that i don't want the line
running uphill at any time?? any suggestions on how i can
get the filter to fit or are there smaller ones available??

 

Even if you drop the fuel line in a U shape below the carb it will still
raise up to the carb and work as fuids seek their own level.

Ian Singer

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No

Think syphons.

 

They do. In fuel taps.

 

Well, yeah, as B12 says, you can't have a massive loop and expect it to
work, but I've frequently had a small loop below the carb and never had
a problem.

 

If the loop acts like a syphon then both legs will attempt to level off
at the same level. That level will actually be gas tank level, and so it
will be applying a slight pressure to the carbs which are lower than the
tank. It is not a real syphon though as the tank level is at
atmosphere, plus a slight pressurization from the weight of the fuel in
the tank, and the other leg to the carb is running at a negative
pressure when the engine is running. if the syphon is full why would
there be any problem getting fuel to the carb? Now an inline filter
could add too much restriction that it would not work.

Ian Singer

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This is true.

Mea culpa.

But it'll still flow fuel, which is the main thing.

 

I've never had carb float bowls full of anything, except petrol. Stale
or otherwise.

The closest I ever got was on an old BMW airhead boxer, whose red lead
paint (inside the tank) was starting to go, and was turning into a brown
sludge, but I had in-line filters on that bike and all it did was block
those.

I really don't see there's much of a problem here. I suppose there is
some stuff that's fine enough to get through the filters on fuel taps on
old-style bikes, but it's only grief on bikes that are really ancient or
have been standing for years, in my experience.

 

Actually, a lot of FI systems bleed fuel, in small amounts, into the
cylinders in order to avoid a jerky take-up when power is re-applied, so
this is wrong.

 

About 5 years ago, I was able to get Plastonics (makers of
"Visu-filters") to make a right angle fuel filter.
GasGas enduro bikes have a short distance from the petcock outlet to
the carb inlet, and they are at a right angle to each other.

I spent the whole three days of the Indianapolis Powersports Expo
visiting with different filter manufacturers and promoting my idea of
the right angle filter.

Three months later, a fellow from Plastonics called the shop and told
me that they were sending me a sample; and wanted my input.

Here is the result:
http://www.rockymountainatv.com/viewLargerImage.do?prodImage=v/vis_07_in_lin_fue_fil.jpg

It is exactly what I asked for.
They make them with screen inside the housing and also one with a
bronze/ceramic unit inside.
They are perfect for my application.