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SuzukiSavage.com
/cgi-bin/YaBB.pl General Category >> Technical Documents/Reference >> Adding a Fuel Filter to the Savage /cgi-bin/YaBB.pl?num=1211846392 Message started by Oldfeller on 05/26/08 at 16:59:52 |
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Title: Adding a Fuel Filter to the Savage Post by Oldfeller on 05/26/08 at 16:59:52 There are 3 positions taken by the various fuel filter experts around here. 1) you don't need a fuel filter. The stock Savage petcock assembly has a filter screen on it already. 2) get any sorta little bitty filter that will fit in the fuel line that currently exists. Anything is better than nothing. 3) use what fuel line that exists as a lead in to a larger clear 10 micron pleated paper filter fuel filter (Autozone sells them) which gets tucked up under the seat where you can still see it and you put in a new piece of hose from the exit side of the bigger filter running back to the carburetor. Big ain't bad nor hard to do either. Note how the new return hose has nice broad bends to it so it won't ever pinch itself off in use. Big clear filter will show you condition of your fuel, graphically illustrates any vacuum petcock issues you may come up on, traps any condensation water from the tank and shows it to you and it also has enough trash holding capacity so it will last for years & years & years without plugging up. Plus you can SEE what's going on .... big plus on this point when you are broken down by the side of the road doing emergency troubleshooting. ================================== The cruxt of these three positions is "do you really want to remove all the small trash and water from from your gasoline or do you want to only take out the big chunks?" http://www.hunt101.com/data/500/medium/fuelfilter.JPG |
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Title: Re: Adding a Fuel Filter to the Savage Post by Oldfeller on 05/26/08 at 17:36:57 Hey, this post is like 5 years old at this point in time. Some additional items have come to the surface so I will share them here and let you ignore the picures and such past this point that show different things. First, hose size and filter nipple IDs -- stay with 3/8 and only go as small as 5/16th at the very smallest. Why? 3/8" is good because the hose is big enough that in the bends it never goes below 5/16ths effective inner diameter. The ID of the 3/8" filter nipples never restrict anything to less than the stock petcock and carburetor nipples already do. Your normal small screw type hose clamps can easily make 3/8" hose grip the petcock and carburetor nipples so that the rest of the system is known NOT TO BE THE FLOW RESTRICTION. Next, the orginal filter style show in the original pictures isn't readily available any more. Your clear sided filters are either FRAM G2 or FRAM G3 filters or else they are the oriental rip-offs of that design type. Note that these FRAM types have a lot more pleats (more square inches) of filter paper than the original filters had. http://www.oilfiltersonline.com/images/products/large/G2_102306.jpg 20 pleats of paper on a side (40 total) FRAM http://contentinfo.autozone.com/znetcs/product-info/en/US/ipc/FF1-4DL/image/2/ 14 pleats of paper on a side (28 total) oriental rip off of a FRAM There are some filters out there with only 7 pleats per side (14 total) so count your pleats before you buy the filter. If you go with the oriental rip off "FRAM" filter, please do a flow through test using a syphon hose on the intake side maintaining only 2-3 inches of vertical drop (gas surface to filter inlet) in the suction system. Some oriental filter paper can be very restrictive, so you are looking for syphon amounts in the order of a cup a minute or better once you get the system flowing at full rate at the designated 2-3 inches of drop. Most clear in line filters of this size did a lot better than this minimum cup a minute rate in Charon's testing. Or, you can do a in-place test on the bike with the hose to the carburetor detached and aimed at the catch cup. You will need to do this when you are well down in the reserve portion of the tank. The pass point is a cup full of gas inside 60 seconds. (a little bit more of a functional test when done on the bike, I think, although you will have to separate out your vac petcock as a potential failure cause if you chose to do it this way and it fails). ===================================================== http://www.hunt101.com/data/500/medium/hose.JPG (note that extra quick clamps were purchased to go over all fuel connections for vibrational security) As you view this picture you will see the stock Suzuki fuel line tubing measures 0.2675" on the inside diameter. This has led some to purchase quarter inch I.D. (0.250") (BAD IDEA) fuel hose, including the example shown. This hose is a tight fit to all the nipples used in this system and is not "easily installed" on the metric carburetor nipple and thus the 0.250" hose is a BAD IDEA so please don't do that to yourself. Others have purchased 5/16 I.D. (0.3125") fuel hose (BETTER IDEA) and have found they got acceptable grip on the nipple fittings and no fuel leakage. You may need to purchase your clear filter first and then consider fitting the hose to the nipples you have on the clear filter, with the slack being taken up at the slightly larger brass carburetor nipple barb. You need to replace the stock Suzuki hose with your new hose to make the run to the clear filter, then use the new hose to go from filter exit to carburetor nipple. Note the use of a long broad loop to make the return run to the carburetor -- this way the hose is never temped to pinch itself shut due to a "too tight" bend anywhere in the curved return run. Clear fuel filters of the type shown in the pictures can be purchased at Wal-Mart in the automotive section (Fram has two clear fuel filters currently hanging up on the wall in the Wal-Mart auto fuel filter section). Autozone no longer sells the exact same looking clear fuel filter shown in the first picture in this thread. 3/8" filter nipples and 3/8" diameter rubber hose is the BEST IDEA because it absolutely guarantees the stock nipples on petcock and carburetor are definitely the "as designed in" restriction points in the fuel delivery system. Use of effective hose clamps is required at the petcock nipple and the carburetor nipple when using the larger 3/8" ID rubber hose. ============================= "Small filters" referred to by some folks as their preferred solutions generally come from Briggs and Stratton type fuel filters (lawnmower section) and from dedicated motorcycle shops. Watch your fuel line sizes as most of these are quarter inch nipple sizes and may require quarter inch fuel hose. Watch out though, as some are 3/8" nipple sizes and won't work for you without downsizing a hose somewhere. The small fuel filters either have a metal or a nylon mesh screen as their active element. This is the exact same thing that exists on your petcock, so don't expect to see any finer filtration or water removal. True micron level filtration requires PAPER PLEATS and lots of them, so look for clear plastic filters in the auto area that have some decent size to them. ============================= Discussion of the rusting of the insides of Savage gas tanks and the need for the larger clear sided 10 micron filter paper fuel filters seems to center around the increasing use of alcohol in cheaper grades of regular gas. This inclusion of alcohol used to be unusual and used to be always stated at the pump, but now this is no longer a requirement in some states. Alcohol is accepted as part of the anti-knock additive packages that may be used in standard grades of regular gas, especially at the low cost distribution points. What is new and potentially frightening to you and your bike is a creeping new technology that is also part of the "anti-knock additive package" classification as it rides right along with the use of alcohol that is used to carry it into the gasoline mixture. Note this is not a new patent, and it makes reference to even older existing patents in the fuel industry. (you need to scroll down several pages to get to the actual percentage of H2O that this technology will support -- yes, that was up to 22% -- you did read it correctly) http://www.freepatentsonline.com/4158551.html And now you know why cheap gas can seem a bit cloudy when you put it in a clear sided container. And also you know why it may be a good idea to put a sizeable clear 10 micron pleated paper filter on your fuel line as the growing intentional inclusion of alcohol as a fuel additive has potential downside consequences for your 1980's designed carburetor system (and your 1980's old style uncoated steel fuel tank). |
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Title: Re: Adding a Fuel Filter to the Savage Post by Oldfeller on 05/05/11 at 08:51:01 Youse guys really are in love with them little bitty filters that have the same metal or nylon mesh style filter system as what already exists up on the petcock. Do you really think these little bitty things with no micron level paper pleat filtration are gonna remove any finer particles or take out any water compared to what is already sitting up in the gas tank on the end of your petcock? The larger auto filters with paper pleats give you finer micron level filtration that will sift out the liquid water and keep it on the outside of the filter paper until you happen to get some "dry" alcohol laden gasoline that will recombine with the excess liquid water and carry it away out your exhaust pipe. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Boule’tard on 05/05/11 at 15:26:30 While some automotive filters may incorporate a water trap, or have one in series with a paper element, I don't think the paper itself can sift out water molecules as you imply. Water molecules are on the order of angstroms (a few ten thousandths of a micron) and a good paper filter only filters things larger than about 10 microns. I doubt the Autozone cheapys are even that good. So unless there's some other voodoo going on with ions or hydrogen bonds or something, paper is not going to hold back H2O for you. Sintered brass filters typically provide 35-40 micron filtration. That's better than a petcock screen and good enough for a carbureted motorbike. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Oldfeller on 05/05/11 at 16:32:42 Both very fine weave cloth and fine mesh paper will separate water from gasoline provided the fabric or paper is wetted with gasoline first. The process of H2O osmosis through the organic fibers cannot take place if a non-compatible liquid is already occupying the fibers. Barring osmosis, the surface tension of the water micro-droplets won't permit them go through the mesh. Now, in the presence of alcohol (which bonds with individual water molecules) and petroleum emulsion/miscibility compounds that are designed to hide water in the gasoline this situation probably breaks down as the water is bonded to the alcohol and emulsified by the chemicals and the water has lost all its surface tension effects. .... so you are likely correct anyway but for a different reason. Boy Scouts used to be taught that a London Fog windbreaker will separate the water out of a contaminated tank of gasoline in an emergency situation -- you folded a pocket recess in the coat and poured the contaminated gas into the pocket. The gas dripped through the fabric into the catch container and the water stayed in the pocket -- that is how it worked back in the day when gas was gas and had no funny stuff in it. We were taught to sacrifice the coat to get the engine running again and get the heck out of whatever jam we were dealing with. We also had matches, belt knives and scabbarded hatchets on our belts and you could get a merit badge for markmanship and another one for hunting .... that was back in the days before being PC was even invented. Scouts built campfires everywhere they went ... Explorer scouts were very skilled outdoorsmen. They dressed well too as London Fog windbreakers were right expensive back in the day. And for those younger readers among us, a London Fog's fabric was kinda like the Gortex of its day as it was breathable, cool and waterproof. Simple Experiment Fold a cone shape into a piece of printer paper (with the center point of the paper being the apex of the cone) Wet the paper with gasoline or kerosene or whatever petroleum liquid you have on hand Pour a little bit of water into the cone and see what happens Add some alcohol so the water is about 1-3% of the total amount of alcohol and see what happens Catch all the alcohol that comes through the paper in a clear bowl and see if you can find your water that disappeared from the inside of the cone |
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Title: Re: Adding a Fuel Filter to the Savage Post by Boule’tard on 05/05/11 at 18:37:42 That makes sense Oldfeller, I had not thought that clusters of water molecules, in solution, might also have their own surface tension, sans water/air interface. And it is those microscopic droplets that cannot pass through the filter until alcohol comes along to grease the skids.. interesting. So moisture will not hang around in the filter thanks to the gasohol that we're stuck with these days. The engine has to pass X amount of water that is in the gas. Is it better to have a paper element in case of a watery non-gasohol tankful, or do you think the filter ought to just pass it? I think the paper one might be better in that case, so's to avoid passing a sudden "slug" of water that settled to the bottom while the bike was sitting. But then if that same slug was sitting in the filter, it seems that would stop up the fuel delivery also. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Oldfeller on 05/05/11 at 19:42:00 I have gotten some off brand watery gasoline that left 1/8" of dirty looking water at the bottom edge of the clear plastic filter by the time a quarter of the tank was done. I worried about it for the rest of the tankful, then I bought some Amoco (now BP) unleaded figuring it was the best unleaded gas that I knew about. The water got quickly sucked up by the tankful of "dry" unburdened gasoline leaving a dirt ring on the clear bowl. This episode caused me to research about water in gasoline and I was amazed that water is being added to cheap bulk gas on purpose now, intentionally and legally as an anti-knock additive. That alcohol (10%) can be added to gas along with some chemicals that allow 3-5% water to be in any 87 octane regular gas which is all legally part of an anti-knock package (here in North Carolina anyway). As noted in the patents referenced up thread, the percent of water supported by these chemicals can go as high as 22% before it comes out of emulsion, so to actually see water in gasoline indicates some serious amounts of water actually being present. We no longer see signs about "Alcohol Added" in North Carolina any more, 10% is expected and is considered normal now-a-days. E85 is coming, expect it as soon as the alcohol supply from the budding organic conversion of bulk saw grass processing plants get built and into full production. With more alcohol comes more water -- the stuff attracts it naturally. Your modern car is smart enough to digest E85 or some seriously watery gasoline, you don't get any ping or other nasty symptoms any more, just some rotten gas mileage. Your car retards ignition, richens mixture automatically if a ping is sensed. Your Savage ain't that smart. A bad load of gas makes your big single run like shite. Really, why you need paper filtration is the trash and rust particles and odd sediments coming from all the steel piping and tankage along the way. Your unlined rusting gas tank (sorry, but it is happening to you) is passing crap to your petcock filter that eventually will plug it up totally. Take your petcock off every few years and blow the screen out with carb cleaner. The fine micron level paper filtration catches all the little trash and the paper will stop a slug of dirty nasty water and hold it until it can be dissolved by a load of good "dry" gasoline. The fact you can see the water sitting in the bowl also helps you with troubleshooting them fuzzy "unknown strange running issues" too. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Boule’tard on 05/06/11 at 19:08:27 Yep, a quarter inch of water in your gas is probably better to have in your filter than your carb bowl. 1) because if the filter is clear, you can see it and 2) that amount can sit there until you get some gasohol to dissolve it, whereas in the carb bowl it'd probably be too much for your engine to start. I'm shocked and apalled there's deliberate water in gas?! Bastards. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Oldfeller on 05/07/11 at 02:14:30 http://www.freepatentsonline.com/4158551.html Take the time to read the whole thing, especially read the applicable patents and dates they went into effect. They are quite old, aren't they? 1960's era to be exact. The petrol industry has been putting water into gasoline intentionally for decades and decades and decades now. Remember, water (in moderation) acts to replace lead as a detonation inhibitor, so look to your off-brand unleaded cheap gasolines to likely have added H20. Alcohol always carries 1-3% water for the alcohol volume, they can't stop it from happening. But that isn't the crime now, is it? That is only roughly 0.3% alky-water to the total volume of gasoline, what we are looking for is the intentionally added 3% of the total volume of gasoline of emulsifier added water. If you ask somebody in the petroleum industry, they say they put the H2O emusifier chemicals into the gas "in case of condensation water being found in tanks". Hard fact, "as shipped" gallons would bring the wholesale distributor $3.70 or more a gallon. If he can mix in an additional 3% of city tap water when he is tankering up a 10,000 gallon tanker truck of a low cost no brand gasoline that already carries 10% alcohol heck that's 30 free gallons of shipped gas he gets paid for. He ships 100 tanker trucks of cheap gas a week, so that's 3000 extra gallons a week. 162,000 extra gallons shipped in a year's time is worth nearly $600,000 each year to his business. If you asked him for a chemical analysis of the cheap gas, the 3% would be legally listed as the emulsifier "compound" (emulsifier and the water) listed under the anti-knock additives. Completely legally now, it is an approved anti-knock additive after all. Now, what do you do with the greedy bastard that isn't going to stop at just the legal 3%? How are you going to know or detect it when his additives can hide up to 22% of H2O if he is sneaking you 5% or 8% or 10%? |
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Title: Re: Adding a Fuel Filter to the Savage Post by WD on 05/10/11 at 06:26:12 Add the clear filter guys. You want proof on other vehicles? My 69 Dodge runs the large clear Fram. I change it once a month. The water and alcohol in modern fuels speeds the corrosion of gasoline storage tanks. I ALWAYS have "sand" in the filter. Or "chalk" dust. Or pieces of dissolved fuel line. My 49 Dodge has a fuel filter sediment bowl at the carb tocatch whatever makes it past the fuel pump. Which also has a sediment bowl. Both are metal mesh screened stock. Both converted to paper replacement elements. Had the 49 running 17 years ago when I first started seeing E10. Bowls were always full of crud. With the sediment screen too much debris got passed into the carb. It is now a paperweight. Literally, the crud E10 forms blocked every passage and hardened solid. And carb cleaner only gets so much of it out. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Oldfeller on 06/10/11 at 15:36:32 If you want your clear filter to appear full all the time, make sure it is positioned so that the filter body is under the petcock's "out" position but above the carb intake position. The exit of the filter needs to be slightly higher than the entrance to more easily flow out an air bubble. Why do you "get air" in your clear filter? Generally 2 reasons, you ran it dry (got you an air bubble the hard way) or you exposed the filter to direct sunlight on a warm day (you got you a gas vapor bubble). Why are neither situations harmful? The filter has an intentional rather large extra amount of EXTRA flow capacity and the needed fuel can flow through just a portion of the filter paper. More than enough fully filtered fuel to keep your Savage running just dandy. (that's why the paper filters last like forever without giving you any issues -- it is also why they can trap and hold large visible amounts of water from some very sorry very poor quality gas and still keep flowing acceptable gas just fine) On a hot sunny day I have seen my bike run fine with less than 1/2 liquid gas in the filter. An hour later it was full, so I think it was a big temporary gas vapor bubble. I have also seem mine run fine a quarter full of dirty looking water which lasted the rest of that tank of gas and scared the shite out of me the whole time. The fact you can see what's going on is nice. For the fun of it next time you hit reserve so strong your bike dies and you have to stop, go ahead pull over put her on the sidestand and eyeball the filter as you switch over to reserve and watch the "flow show" through your clear filter -- amusing to see the new fuel rush on through (raptor) or jest barely trickle in (stock vac petcock). |
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Title: Re: Adding a Fuel Filter to the Savage Post by Z on 06/12/11 at 13:25:34 Here's what mine looks like right now. Another example of a correct installation. http://i804.photobucket.com/albums/yy323/Zaney1/Bikes/DSC01308.jpg |
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Title: Re: Adding a Fuel Filter to the Savage Post by Oldfeller on 11/11/12 at 01:19:32 GyroBob had a better implementation idea when he was building his RYCA bikes. Notice his larger hose size and his direct "down" orientation, which was all made possible by the relocation/re-routing of his huff tube. If you can move your huff tube upwards (or re-route it) you can do it this way too. http://i258.photobucket.com/albums/hh253/Gyrobob_theOriginal/KampNfuelfilter01b.jpg This filter can be bought several places (K&N is one) but the normal filters we have been using can work in this orientation if you go with the larger hose sizes and clip off the reduced end sections and shove the hose all the way on. This installation winds up with the pointy end up and it tends to void all the air bubbles on fill up naturally. http://suzukisavage.com/yabb2.2/Attachments/IMG_0838.JPG clip off the 1/4" ends and use a 5/16" hose NOTE and WARNING: The stock vacsucker petcock does not seem to love any form of in-line fuel filter, mainly because the vac petcock won't supply enough gas to fill the system up again rapidly after it has done you dirty and stopped you by the roadside by doing the infamous "running you dry" trick. YET ANOTHER REASON TO GET RID OF YOUR STOCK VAC PETCOCK !!!! |
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Title: Re: Adding a Fuel Filter to the Savage Post by HighME32 on 10/28/14 at 12:04:15 Does anyone have any bad experiences with the fram g3 filter, which I believe has 3/8 inlet and outlet? How often do you guys replace them and can I do the same routing as the fellow with the ryca setup using 3/8 fuel line? |
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Title: Re: Adding a Fuel Filter to the Savage Post by HighME32 on 10/28/14 at 22:06:13 There is no way this Fram G3 fuel filter will fit. It is massive. I just bought it from Walmart today along with 3/8 fuel line. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Oldfeller on 10/29/14 at 05:20:34 http://www.hunt101.com/data/500/medium/fuelfilter.JPG Use this method and it will fit -- just move it back some. |
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Title: Re: Adding a Fuel Filter to the Savage Post by HighME32 on 10/29/14 at 13:51:15 I thought of that, but I dont think I can make that happen with this filter. I have a ryca cs1 and the k&n filter takes a lot of space underneath there. I was also thinking of copying the other ryca owner's setup, but this filter would have to hang outwards and mynleg would rub against it. |
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Title: Re: Adding a Fuel Filter to the Savage Post by HondaLavis on 11/21/14 at 18:38:59 This filter ultimately had problems with vapor lock on long rides. There may or may not be a way to make it work, but at this time this is NOT a proven successful method. If I ever get this to work long term, I will update this posting. http://i230.photobucket.com/albums/ee291/Lavis325CL/20141121_164858_zps77420561.jpg http://i230.photobucket.com/albums/ee291/Lavis325CL/20141121_164905_zps43cf6f66.jpg This IS a large filter. Each one of those nipples is almost an inch long out of the box. The outlet to the carb I trimmed off until I had approximately 0.5 inch remaining. With my parts laid out, you can see it does not require a lot of fuel line. From the tank to the filter I used approx. 1.9 inches of line, and from the filter to the carb approx. 1.5 inches. On the inlet side of the filter, the line is only mounted 0.75 inch down. The length of the line pushes the filter back so that it doesn't interfere with the choke knob. Going into the carb, the line will take a bit of a slant, but it is't too sharp. Make sure that you use clamps to handle some of the stress of the bend. In the end it does just barely touch the choke knob in the normal running position. The finished project: http://i230.photobucket.com/albums/ee291/Lavis325CL/20141121_171644_zpsed038709.jpg You can also use the WIX 33087, as it's the same filter. There are versions of this filter with the same part number where the inlet nipple is positioned 180 degrees to the other side of that end - in line with where my index finger is in the picture. I'd imagine that this version would be easier to install without interfering with the choke, but it may need more line. For a whopping $5 at my local NAPA, this is an easy piece. I hope this can help somebody. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Rodger on 12/28/15 at 16:02:33 I tried O'Reilly, Advance Auto, & AutoZone "dot coms" and couldn't come up with a Fram G2 at any of them. Finally found it on walmart.com, $2.93 + tax with free in-store pickup. Will get some 5/16 & 3/8" hose and install when I have the tank off for the 600-mile break-in service...photos to follow. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Kris01 on 12/28/15 at 18:57:16 Rodger, just FYI, most fuel filters have become problematic in the long run. Your mileage may vary. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Rodger on 12/28/15 at 19:48:45 Problematic how, Kris? Leaks? Fuel contriction? |
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Title: Re: Adding a Fuel Filter to the Savage Post by Dave on 12/29/15 at 07:37:38 585640424A4C472F0 wrote:
The fuel flow in the Savage is by gravity, and since the fuel level isn't much more than a foot when the tank is full....there is only about 1/2 psi of fuel pressure when the tank is full - and even less than that when the fuel level is lower. The problem that occurs is that an air bubble can become trapped in the small passage in the hose fitting on the filter. The plastic needs to be pretty thick to have any strength, and it is easy for an air bubble to become lodged in the small diameter hole.....the fuel wants to flow down past the bubble - but the bubble wants to go up and the bubble prevents the fuel from flowing...it creates an "air lock". When you install the filter and first hook it up - it could work fine, and then at some inconvenient time/place you could potentially get a bubble stuck and cause you problems, and since it has been working for 6 months without a problem you most likely won't expect that the filter is causing a problem. I keep my tank and carb clean, and I don't use an additional inline filter. The filter has the potential to cause running problems, and it also has the potential to break as it is only made of plastic. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Kris01 on 12/29/15 at 16:46:35 Dave, just playing Devils' Advocate here, what do you think about using an oversized fuel line? Say about 3/8"-1/2" or so. It would give the gas more of a chance to make it to the carb. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Dave on 12/31/15 at 04:57:21 437A617B3839080 wrote:
The fuel line is not the problem - it is the nipples/barbs on the fuel filter that are so small that they create the "air embolism". If you could find a filter with the larger nipples, then maybe the filter could work reliably. I am not sure how big the nipples would need to be to provide the same size hole as the original 6mm (1/4") fuel line - but I suspect that by the time you obtain a filter with a 5/16" or 3/8" ID on the nipple - the filter is going to be too large to use on the Savage. Look at the post that HondaLavis posted above.....he had a larger filter with 5/16" nipples, and it proved not to work reliably. |
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Title: Re: Adding a Fuel Filter to the Savage Post by ThumperPaul on 01/04/24 at 09:06:39 I'm digging up this old post as I am/was considering adding an inline fuel filter to my set-up. I can understand why Suzuki probably didn't include an inline filter due to the vacuum needs of the stock CV carb (air bubbles no bueno). But for those of us that have ditched the stock petcock valve and gone gravity fed (be it a Raptor petcock valve or otherwise), considering adding a second line of defense with an inline filter is an interesting dilemma. I'm not smart enough to question the science and wisdom of if a paper filter or sintered brass filter can prevent water from entering the carb/engine. That was an interesting debate and discussion above with Oldfellar. And we're all virtually stuck with gas containing 10% ethanol these days. I can get ethanol free, but I'd burn a 1/4 of gas back and forth to that special gas station - not practical and not possible when out of town in the boondocks. I'm inclined to forego an inline filter and avoid the possible problems sited in this thread. Suzuki didn't seem too worried about small crap getting past the petcock valve filter/screen. Does something like Sta-Bil or Iso-HEET mitigate concerns about water in the gas and tank? I can't say I've ever had a problem with really bad gas and always buy from "Top Tier" gas stations whenever possible. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Dave on 01/05/24 at 04:38:21 The stock and Raptor petcock both have filter screens on the inlet tube, and the carb has a filter on top of the seat for the float needle. Adding an inline filter is a huge restriction to the amount of fuel flow that is available....and even more important is how easily an air bubble can get stuck in the small diameter of the filter nipple. With fuel line/filters so small - a little reduction in ID can greatly reduce the area that fuel can flow through. (I will go out and measure some filters and put some numbers to this). |
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Title: Re: Adding a Fuel Filter to the Savage Post by ThumperPaul on 01/05/24 at 06:04:46 Good points Dave. No adding an inline fuel filter for me. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Ruttly on 01/08/24 at 11:26:12 The only time I run a filter , is first start , maybe thru initial break in. Only because who knows what might come out of a tank. After I’m satisfied there are no issues , it gets tossed. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Dave on 01/23/24 at 06:01:03 It is a rainy morning and I spent a little time doing math. I used my center finders to determine the ID of the carb inlet and a few fuel filters. The stock fuel line is 8mm - 5/16" is very close (1/4 is too small). The fuel line has in ID of 0.3150"...the area is 0.0373 sqin. The inlet nipple on the carb has an ID of 13/64' which is 0.2031", and the area is 0.0324 sqin. A 5/16" fuel filter has a nipple with an ID of 5/32" which is 0.1563", and the area is 0.0192 sqin. A 1/4" fuel filter has a nipple with an ID of 9/64" which is 0.1406", and the area is 0.0155 sqin. The results are that if you install a 5/16" fuel filter the flow area in the nipple is only 59% of the carb inlet, and a 1/4" filter has a flow area in the nipple of only 46% of the carb inlet. This reduction is a result of the thick plastic used when making a fuel filter.....the brass carb inlet is much thinner and it has a far greater flow area. |
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Title: Re: Adding a Fuel Filter to the Savage Post by Dave on 01/23/24 at 06:03:23 Here is an example of the size difference of the carb inlet diameter and the 5/16" fuel filter (a 1/4" filter is even worse). |
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Title: Re: Adding a Fuel Filter to the Savage Post by Dave on 01/23/24 at 06:23:11 The attached photo shows the center finder diameters for the fuel inlet and a 5/16" filter. There is no doubt that the biggest restriction to fuel flow is the small hole in the float needle seat.....that is the smallest opening in the fuel system. The big problem is not that the smaller diameter hole on the filter restricts the flow of fuel - the problem that occurs is the small diameter nipple can often trap an air bubble that blocks the flow of fuel. When air is in the nipple the fuel pressure from gravity flow from the fuel tank is not high enough to push the bubble down - and the air bubble does not have enough "lift" to come out of the nipple and flow upward. The fuel system gets an "air embolism" and your carb doesn't get any fuel.....and this bubble can form days/weeks/months after you install the filter and leave you stranded and looking for ignition/carb problems that don't exist! |
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Title: Re: Adding a Fuel Filter to the Savage Post by Dave on 01/23/24 at 06:25:48 The fuel system operates under very low pressure - gravity cannot provide much pressure when the distance from the float bowl to the top of the fuel tank isn't much more than a foot......the bottom of the fuel tank less than half a foot. With a full tank the pressure at the carb is less than 1/3 psi......with an nearly empty tank it is less than 0.15psi! |
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Title: Re: Adding a Fuel Filter to the Savage Post by ThumperPaul on 01/30/24 at 10:49:19 I like the math reasoning (area of a circle pi r sq stuff and psi)! Along these lines, what is the diameter of the float valve feed? Ultimately, gas has to squeeze through there to fill the bowl. I don’t know the size exactly, but I think it’s 3.3mm on a Mikuni VM36. Vacuum locks and air pockets. It’s easy to see happen with a clear filter. Question (and for a change I don’t have a related problem!): isn’t it possible for the fuel line itself (no filter) to get a vacuum lock or air pocket? Can the air pocket be removed by removing the gas cap and running the bike run a couple minutes. Get it to burp? Or am I worried about nothing and solving a problem that doesn’t exist? |
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Title: Re: Adding a Fuel Filter to the Savage Post by Dave on 01/30/24 at 14:31:09 5D617C64796C7B59687C65090 wrote:
The fuel line and factory petcock/carb nipples are large enough that that an air bubble can freely move upstream and exit the fuel system. The small fittings on the fuel filters are small enough that the bubble can be trapped and it will not freely exit....the fuel wants to come down and I believe the surface tension of the fuel is stronger than the small air bubble - and the flow stops. This situation evidently can't be resolved in normal operation, and some members have even had this occur after using a fuel filter for an extended period. When they first install the new fuel filter the tubing and filter are empty - and the fuel flows down the tube and pushes the air out the bottom. After that the fuel system is subject to periods where the bike is not being stored and air gets into the system from the carb end and the air travels up the tubing until it reaches the small fuel filter inlet.....and that is where it gets lodged and stays. The rider is suddenly at a loss as to why his bike has stopped running, and he starts looking for electrical problems and carb problems that don't exist! Your fuel petcock has a fuel filter screen in the tank......and the carb has a fuel filter screen on top of the seat for the carb needle. If both of those are in place and working....I really don't see the need for a third filter - especially when they can be problematic. Over and out.....if you choose to run a filter - you have been warned! ;) |
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Title: Re: Adding a Fuel Filter to the Savage Post by ThumperPaul on 01/30/24 at 15:01:17 Good answer, Dave. I've already said I won't use an in-line fuel filter based on the problem noted. I'm fine with the petcock screen in the gas tank and the little screen in the carb. I was just thinking the fuel line itself could develop an air pocket. And that you could probably get it to burp out of the fuel line and into the gas tank if you removed the gas cap and fired up the bike. Glad you think this isn't likely or necessary and the line clears itself through the petcock and into the gas tank. I like that answer. It's consistent with my thoughts, but I needed something new to worry about on Woody. |
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