TOPIC:

I was cleaning the rust out of my gas tank last night and I took the petcock out and was inspecting the filter on it for rips & tears.

A thought occurred to me: how does rust get into my carburetor even though the very fine filter on the petcock is in good shape and I have an inline fuel filter? The rust flakes that show up in the carburetor bowls can sometimes be fairly large - much much larger than you would think could get through the petcock filter.

Is the vacuum pressure just so high in the petcock that it can suck particles that thru openings that are much smaller than the particle?

Engine vacuum doesn't pull fuel from the tank. Engine vacuum actuates a diaphragm to allow fuel to flow by gravity, then a spring returns the diaphragm to the closed position when the engine is stopped. I don't know how larger particles would get past the petcock screen.

Even with the screen & since you're getting large particles in the carburetors, it's usually recommended to install a motorcycle in-line fuel filter.
Keep in mind that some fuel filters from the auto parts store aren't suitable for a motorcycle.

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I use a Golan Super Mini 5/16" fuel filter (70-312G 5/16 Barbed Fittings). They are not cheap, but one will last a lifetime; I got mine from ronayers.com. They use a stainless steel filter element that can be cleaned. They filter out very small 10 micron particles but still pass fuel at a rate of 6 gallons per minutes – MORE than enough for any bike. They are very small so they fit well under the tank. Also, I used a 5/16” stainless steel elbow to make the bend from the tank to the cabs so there is zero chance of the fuel line pinching. I got it at a place that specializes in propane supplies. Ed

I don't use an in-line filter any more, but if I ever decide to do so again, I'll probably go with a metal one >> probably a Russel fuel filter w the removable screen so that it can be cleaned or replaced. I had been using a clear plastic one from Z1Enterprises (see pic), but the plastic became soft >> the ends were bendy. This occurred several years ago & I assume it's still a problem. Z1Ent sells a more squat clear filter that's supposed to be able to withstand the fuel/ethanol.

not recommended: fuel softened the plastic.

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I've had no problems with them.
Steve

Does the fuel you use have ethanol? I'm guessing that's why the plastic became soft as I don't use any fuel additives. I think someone else here on KZR reported the same problem with that fuel filter.


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Ed talked me into the Golan after reading about micron sizes........ the slim line filters are mostly rated at 70 micron removal vs the Golan at 10. Rust is rated at 4 to 20 microns, cement dust 3 to100........ dust in the air 3 to 40, the finest sand 60 microns, hair is 70 microns, anything under 40 is too small to see.

How ever small rust particles are, there is always a risk that they end up in the bottom of the carborator bowl (by gravity). If there is just a little bit of water in the fuel, the water will accumulate in the bottom of the bowl where the rust will glob up to larger flakes and eventually block a jet or even worse the float needle.
Unfortunately there is no easy way out. You have to derust the tank, clean the petcock, change all fuel hoses, clean the carbs all over again in order to sort the problem out.
//A

martin_csr wrote: the plastic became soft >> the ends were bendy. < snip > s supposed to be able to withstand the fuel/ethanol.
not recommended: fuel softened the plastic.

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I have one of these cheapies on my sled. (Some days I think Steve is spying / copying me, Ooops, I mean "surveiling" LOL )

I haven't experienced any noticeable problems. As with any cheap filter, there is always a chance that the sintered bronze filter element may not be sealed against the filter housing, allowing debris to pass. I like Ed's metal filter though. Also a small magnet taped to a plastic filter on the input side would attract any iron oxide to that area.

Clean fuel is essential for a good running bike (anything really) , so perhaps cleaning the tank with a non-corrosive chemical and a good flushing would work wonders.

At $5 a pop at a local bike shop I can afford to replace them once a year. The first ones last 3 years. Still have them as spares. Only thing that happened one bent with the heat so it made it's own angle rather than kinking the fuel line. I thought they were restricting the fuel when I went on reserve but it turned out the vent was clogged. I've always used them and always will.
Steve

KZB2 650 wrote: Ed talked me into the Golan after reading about micron sizes........ the slim line filters are mostly rated at 70 micron removal vs the Golan at 10. Rust is rated at 4 to 20 microns, cement dust 3 to100........ dust in the air 3 to 40, the finest sand 60 microns, hair is 70 microns, anything under 40 is too small to see.

Hmm I didn't realize rust was that small, but that's very useful info! It probably just looks bigger than it actually is because it all clumps together in the floatbowls.

650ed wrote: I use a Golan Super Mini 5/16" fuel filter (70-312G 5/16 Barbed Fittings). They are not cheap, but one will last a lifetime; I got mine from ronayers.com. They use a stainless steel filter element that can be cleaned. They filter out very small 10 micron particles but still pass fuel at a rate of 6 gallons per minutes – MORE than enough for any bike. They are very small so they fit well under the tank. Also, I used a 5/16” stainless steel elbow to make the bend from the tank to the cabs so there is zero chance of the fuel line pinching. I got it at a place that specializes in propane supplies. Ed

I currently use the plastic one that martin_csr has had issues with. Mine is practically brand new though, so I'll probably keep using it for a little while then move up to the Golan. I gotta get the bike running first -___-