How Does A Vacuum Petcock Work

Constant velocity carburetors were invented by English motorcycle racers, but they are now called Keihin carbs after the Japanese manufacturer that first mass-produced them. I've got a new set of float needles and seats on the way, but that'll only take care of half of my problem. Bike runs great and no issues but I would prefer a petcock that I can actually turn off. Here's the back of the petcock. Rebuilding Yamaha Vacuum Operated Fuel Valves (Petcocks. It will sit there and allow you to remove the petcock without spilling gas. 2002vulcan classic original petcock has 3 hose connections-fuel,pri,and res. The diaphragm on the petcock, which shuts ( if not dirty, corroded or with a bad oring seal) with no vacumn. We carry pressure relief valves, backflow valves, vacuum breakers, rough-in valves, in-line check valves, gate valves and water valves so you can keep things in check. You can do this with a vacuum tool or by mouth. 5mm fuel hose). I thought having 10 would be a lifetime supply, but no, between leaky ones, ones that the stupid lever froze on and broke off ect, I finally abandoned them all in favor of the vacuum setup after mixing and matching parts until I was blue in the face. necessary? The vacumn on the SV operates two things. Usually vacuum petcocks fail because the diaphragm gets split and/or the vacuum line to the petcock gets disconnected or splits. a lower cost alternative to new honda. Grab your battery charger (and a battery if using an automatic charger). Too long a delay in opening the vent causes increasing vacuum. Or try the pingel. I pried off the metal face cap with a flat screwdriver. You need to use the prime position to bypass this and fill the carbs when it isn't running. capped the vacuum port on the fuel petcock, and the vacuum port on the carb, done. Does fuel flow? If not, your petcock is plugged up somewhere. and nothing worked. The easiest way to get rid of it is to run a line from the gas tank to the carburetor (always put a fuel filter in that line), then pull the hose from the port and use a specially-made AFP plug to close the port. Also found out that wetting the inside of the vacuum hose with spit sometimes has the effect of restricting the vacuum. Do not park it in the "Prime" position because when the float valve that closes the inlet wears out you will overfill the bowl and have fuel running into the sump just as if you left a manual petcock in the "reserve" position. If your bike is equipped with a vacuum-actuated petcock (most Nighthawks are), when the petcock is in the "on" or "reserve" position, it must see a vacuum to begin fuel flow. does bypass the vacuum operated shutoff and it draws from. One final option is to replace a faulty stock petcock with a vacuum-style petcock which has a true "off" position instead of prime. This works sometimes and the trapped vacuum will keep the petcock open. So I reattached that line and tried starting the bike again. The factory clamp was bottomed out-but still a leak (I did not know existed)The hose is too big to clamp down good. The engine will not run with the vacuum port open. If the vacuum hose is leak free and has good connections, the petcock is faulty. They have a vacuum operated slide that changes the diameter of the main opening, called a venturi, in the side of the device. A driver's Backrest that mounts to the Fender Stays. This is a very simple procedure detailing how to restore a petcock without having to purchase any new parts. With the bike running, failing petcock isn't an issue unless it's leaking into the vac line. You should have one vacuum line going from the fuel petcock usually to the intake manifold. - Remove petcock from tank and place the 2 screws off to the side, but trash the large o-ring that sealed it to the tank. If radiator cap is OK, coolant level should be 25-50 mm (1-2 in. Some aftermarket ignitions such as the DYNA 2000, bypass the VOES altogether. My zl600 didn't have a petcock when I bought it and I just recieved this one from eBay, says it's for a kz440 and a couple other Kawi's. In the rebuild kit you will likely have a new set of o-rings, gaskets, a longer spring, and new piston assembly attached to your two rear gaskets. I f your petcock has a "PRIME" position, it is a vacuum actuated type. The petcock on the 454 has a diaphragm pump in it to pump fuel and those are known to go bad. Proper draining. plus a replacement diaphragm and spring for the Kawasaki's vacuum-operated petcock. Close it tight. Check the hand pump every now and again to make sure it's between 10 and 20 in-hg. My question to those more learned than I is why do I need a petcock anyway? The bike seems to run fine when I plug the vacuum tube (26) and just feed fuel into the carbs directly (bypassing the petcock altogether. Please Note: May not work with vacuum petcock. He has been writing primarily since 2005, but did author the book, "The White River Ranger District Trail Guide" in 1988. Ok is the petcock dripping at all? If so you need a new or rebuilt petcock. I have a question on steps 4 and 5 though - how have you found that to work, does it matter you're feeding both carbs from one petcock? As I type I realize that's probably a dumb question but it's better to ask now. this is the part im referring to just so we can be on the same page ill take a few photos of the petcock when I get home from work and post them. Do not park it in the "Prime" position because when the float valve that closes the inlet wears out you will overfill the bowl and have fuel running into the sump just as if you left a manual petcock in the "reserve" position. Open carb #1 drain screw until a steady stream of fuel flows. In particular, the diaphragm should be handled fairly gently. Remove tank and invert or siphon. It has at least three positions: ON, OFF, and RESERVE. Either drain the gas tank into a fuel can by or remove the tank and prop it up so that the petcock side is not submerged in gasoline, remove and disassemble the petcock. Or can a malfunctioning vacuum petcock do both flood or starve a carburetor? I do not seem to be getting fuel supply to the carburetor. The rear carb has a vacuum line to the petcock, the front carb vacuum port is plugged, doesn't have a hose unless one was added for carb synching. The front forks are pretty standard fare, but they work well enough for the non-discerning rider. As long as you didn't puncture anything, the vacuum, if there is one, should function normally when things are put back. I "had" like 10 manual petcocks for 1977 KZ650s at one time. These petcocks are vacuum operated petcocks. Hi there i had the same issue with my 1200 trophy a standard fuel tap wont work as it dosnt provide enough fuel on hard acceleration as the petcock pumps the fuel , try running it on pre as this is free flow setting for priming the carbs other wise you can get a seal and diaphragm kit for the petcock which solves the issue. Reattach the fuel valve to frame, and connect the two fuel lines to the tank. The most common application of a petcock in an automobile is as a drain plug for a radiator. and my rear holder has a line from the petcock, for the gravity fed system. This is very ugly. Couldn`t do that trick on my Dyna and from looking at this petcock it won`t do it either. First connect the rear one and put the clamp on, then connect the front one and put the clamp on. It seems like the vacuum signal from the carb is what keeps the petcock open, when the motor dies, the valve closes, thus shutting off the fuel supply. I didnt have the time or money to invest in it. Yes unless you change the petcock to a gravity fed like a pingle The stock HD petcock requires a vac line or it won't flow Just go to an auto parts store and get some vac line hose and cut it to length and you will be fine Sent from my iPhone using Tapatalk. But how does sous-vide cooking really work? First step: vacuum packing. Read up on the latest news and get great tips in this collection of Snapper related articles. Thank you for visiting Parts N More! It's our goal to make it as easy as possible for you to find the perfect part for your vintage motorcycle. Without proper preparation, your sprinkler system might be damaged by freezing temperatures. So I did the Hurricane mod and it worked fine, but I switched tanks and went to a Yamaha petcock from a WR400, which won't work on a stock tank, but is same as the Raptor petcock except a shorter stock. How does the stock petcock have much to do with fuel getting into the oil? Doesn't that mean the primary reason for concern is that seat in your carburetor? I had a MX carb on my old DRZ, and the thing only ran on prime because it didn't have the vacuum line hooked up. In the rebuild kit you will likely have a new set of o-rings, gaskets, a longer spring, and new piston assembly attached to your two rear gaskets. If you have a late model bike with the vacuum line connected to the fuel petcock, make sure the hose is connected. the carbs fill up and slowly the gas trickles into the cylinders and seeps past the rings and into the crankcase or The other possibility is of course that there's a leak in the petcock diapragm and the fuel is being sent directly down the vacuum line. Every time the piston goes down, it creates a pulse of vacuum to allow gas to enter the carburetor bowl. I have blocked off the vacuum line with a bolt so it wont be to hard to swap petcocks and hook the vacuum back up. If you have an air leak, the suction sucks air in through the gap between improperly joined parts instead of through the carb, which makes your fuel/air mixture more lean. I just hadn't thought about going to a single petcock for both carbs. It should be to short if I remember right. sharp scissors work well on fuel line. If there is not a sufficient vacuum signal coming through that line the fuel flow will be stopped or insufficient. What it does is when the bike is cranking over it sends vacuum though this hose and operates a diaphram in the petcock causing fuel to be released in the fuel line. There is the potential of the diaphragm forming a leak & then not allowing enough fuel to flow to the carbs/engine, etc. what do i set my petcock on a 2003 zr-7s. This configuration is used on both Sportbikes and Cruisers, so to determine if your bike has one, some investigation may need to be done. Or try the pingel. Fuel filter doesn't look too bad. 2007 Kawasaki Dirt Bike KLR650 (KL650A7F). Most now have an automatic, vacuum operated petcock (that may include a prime position which bypasses vacuum operation and allows fuel to flow to the carburetor without the engine turning over). This article was co-authored by our trained team of editors and researchers who validated it for accuracy and comprehensiveness. An inline fuel filter helps ensure contaminants in the tank or fuel don't plug the carb. Whether you're looking for a rebuild kit, a repair kit, a brand-new petcock or a single valve, you'll find it at BikeBandit. The carburetor for the conversion should be in known working condition (if used) and include a enricher (choke) cable. No running engine, vacuum or serviceable petcock then no gas flow. How does the stock petcock have much to do with fuel getting into the oil? Doesn't that mean the primary reason for concern is that seat in your carburetor? I had a MX carb on my old DRZ, and the thing only ran on prime because it didn't have the vacuum line hooked up. If you suck gently and no fuel flows, it's bad. Also, the '86 is a gravity fed system from the get go vs. One final option is to replace a faulty stock petcock with a vacuum-style petcock which has a true "off" position instead of prime. Lots of guys eliminate the valve and just remember to turn the petcock off EVERY TIME. By looking at other posts, fuel should not come out unless there is a vacuum line attached and the engine is creating a vacuum. When the fuel stops flowing, switch the petcock to the RES position. What exactly is the problem you are having? How do you know the gas is not flowing at a steady rate? How do you know it is the petcock and not something else (like fuel line routing)? Check the vacuum line for cracks. Others allow it's usage. The fuel pump can use two tubes. Pull this hose to the left side of the bike and then disconnect this entire bit (3 hoses and 1 “T” fitting) from the remaining “T” fitting which goes to the petcock. This is a simple diaphragm, which pumps in and out by air flow. It has at least three positions: ON, OFF, and RESERVE. It is a fair bet that your vacuum line to your petcock is off. Went ahead and got myself a rebuild kit. To reiterate what I said in your previous thread, my personal preference is the stock petcock, it is a good quality part, and really, a tried and true design. Some folks claim that this won't work. How to cut and modify you stock seat. My petcock is leaking from the vacuum diaphragm. He also explains the difference between on, prime, and off as well as a quick. This counterweight is not meant to move, jiggle or rock unless there is excessive pressure in the canner. fix the leak because it won't open up all the way and allow full fuel flow to the carb. Also replace the two small O-rings on the bolts for the petcock part# 92022. Bike runs great and no issues but I would prefer a petcock that I can actually turn off. As requested, here is the nipple on the right carb where the petcock vacuum should connect. If you find it is the petcock, a $30 rebuild kit would be a better option. ON= main tank, vacuum controlled (normal position) RES = reserve tank, vacuum controlled PRI = main tank, vacuum bypass. Do not forget to: connect petcock vacuum hose to left carb. With the petcock set to on, pull the top hose off the petcock, does gas spew out? That hose should be vacuum. The problem is that you have to use large hose to fit the Petcock and then really clamp it down on the carb. I've attached a picture of my petcock. The 1987 fuel petcock (PN 16950-ML8-601) is definitely a different part than the fuel petcock (PN 16950-MG9-005) for a 1984, 1985, or 1986 GL1200. This video explains in detail what to look for in a failing vacuum operated fuel cock and how to convert to a. the fuel pump system on the '84 & '85 (as noted, Jamie D's site covers the '84/'85 modification to a gravity fed 'on-off' system). Yes, bypassing the vacuum shutoff is the right idea in principle. I bought one that was used on the older King Quads. In the meantime, you can add vacuum to the vacuum line and then try and plug it quickly. i understand this works off of a vacume. Open carb #1 drain screw until a steady stream of fuel flows. Keeps fuel from flowing continuously if the float gets stuck. Get a container and hold it by the petcock, pull off the lower hose, does gas spew out? Gas should drip from the hose. The petcock from an LT160 will bolt right on with the right size fuel line and the ability to turn it on and off manually, plus it costs less than the one for the 80. Add the proper fluid if necessary. You will use the plastic block and diaphragm assembly in the conversion, so take care when separating the pieces. It shouldn’t be able to get past this barrier, and once it does start happening that fuel finds itself into the engine compartment. Safety Petcock 1/4” (6mm) HP Ball Valve Designed with a large, easy to reach handle, the red Elcometer safety petcock valve fits to the Elcometer RCV4000 and RCV4000+ remote control valves. Leaking Vacuum Lines make it sporadic. About Our Best Motorcycle Petcocks. With a wide range of inventory to choose from and fast shipping in the continental US, we’ve got all your GS550 needs covered. Re: Vacuum petcock on SV. The petcock is vacuum operated. I still have the petcock in the trunk of my PC to serve as a warning to other parts that might give me trouble. This is the vacuum hose that got disconnected when dropping the airbox into the frame. Re: Convert Vacuum Petcock to manual. or what can i do to find out Update: yeah im working on a low budget so i need some help that will leave me some money. Hello I recently bought a 72 R50/5 (first BMW) It had sat for a little while so I disassembled and cleaned the carbs (with deluxe rebuild kit) I have a question (issue) with what is the correct float height?. I think in the meantime I'm going to install an in line shut-off valve for the fuel so I don't blow my garage up, and burn down my house. Yeah, just get a petcock with on/off switch to replace the vacuum operated petcock. 5) Buy a new '86 petcock. Automobile. You will also need to plug off the nipple on the carb-to-engine boot (#3), to which the vacuum line to the stock petcock attached to. The front forks are pretty standard fare, but they work well enough for the non-discerning rider. It should be to short if I remember right. How does the "reserve tank" work? A common misconception among new riders is that there is a "reserve tank" on a motorcycle which is actually a separate tank from the main tank. 6) Cut two short lengths of the old vacuum line and plug them with a bolt that fits tightly. Put the long vacuum line on it and suck on it, fuel should flow from the petcock. Leaky Fuel petcock shut off valve I have searched the forum and found handfuls of information, however I am still at a loss and nowhere did I find some pictures to help me understand what I can do to seal my shut-off valve. However, it wont work if the vacuum diaphragm is damaged/leaky as the vacuum will bleed off after a bit. The factory clamp was bottomed out-but still a leak (I did not know existed)The hose is too big to clamp down good. Find quality backflow preventers & vacuum breakers online or in store. I have blocked off the vacuum line with a bolt so it wont be to hard to swap petcocks and hook the vacuum back up. 4 Gallon - fits '95-'03 XL This gas tank comes complete with mounting hardware and rubber grommets and has approximately 3. If you suck gently and no fuel flows, it's bad. My KTM will sit for weeks with the gas on but the needle holds the fuel in the carb just fine. Basic Vacuum Tank Repair. Shop for Fuel Tanks, like K & L Fuel Petcock Repair Kit at Rocky Mountain ATV/MC. if there is it would have to be a pre '80-'81 street bike, one of those yrs is when the govt mandated a vacuum petcock for all street bikes, or it could be from an off road bike/atv any yr and any manufacturer. Keep in mind the 450 has a vacuum petcock. What it does is when the bike is cranking over it sends vacuum though this hose and operates a diaphram in the petcock causing fuel to be released in the fuel line. My petcock is located in-line between the fuel tank and the carb. If I do a radiator flush as you suggested will that clean my heater core at all and how well in comparison to a direct back flush. This is very ugly. It has at least three positions: ON, OFF, and RESERVE. The anatomy of a petcock problem This is a generic description of the Suzuki vacuum-operated petcock. Do the same in sequence for #2-#4. That can save you some valuable time and money by allowing you to do it yourself rather than scheduling a service appointment. Turn the petcock to the prime position. Generally a small vacuum line is attached to the number one cylinder vacuum port. Drain fuel from tank. Awaiting all of the should’ve bought Behr comments I’m sure. Items which have been used or installed will not be accepted for refund. My Virago has a vacuum operated valve and instead of off, there is a "Prime" position that draws from the reserve but does not require vacuum to flow. So I did the Hurricane mod and it worked fine, but I switched tanks and went to a Yamaha petcock from a WR400, which won't work on a stock tank, but is same as the Raptor petcock except a shorter stock. How You Can End Up With A Piston Full Of Gas: What happens is that the fuel leaks down past the gasket in the fuel vacuum petcock. After many attempts I could not repair the vacuum leak internal to my petcock & when parked it would always weep gas into the carb. Actually, the vacuum port DOES have a check valvein the vacuum section. Hope that helps. Since the engine will likely quit shortly in a "down" situation, this petcock will automatically close and prevent the fuel from flowing out. The most common application of a petcock in an automobile is as a drain plug for a radiator. Run both left and right fuel lines through a "T" to the vacuum valve fuel "in" port. Find the Drag Specialties 22mm Chrome Petcock - 0705-0282 at Dennis Kirk. Modify a Harley Engine Guard to work with Ziv's control relocation kit. Reattach the fuel valve to frame, and connect the two fuel lines to the tank. necessary? The vacumn on the SV operates two things. Activate the engine starter motor and turn the engine over. Thus, if the pressure in a system of potable water drops, it is possible that non-potable outflow could backflow into the system, ruining the water. Inspect the vacuum hose if the vacuum petcock fails to operate. If it sticks to the metal pieces, and it likely will, use your fingers to gently work it off. Turn cap SLOWLY. Then consider that it lives at the bottom of the fuel system below the tank. ) I also noticed there seems to be a vacuum line going from the petcock to the #2 cylinder intake manifold and the petcock seems to have a vacuum diaphragm. The fuel pump also has a QR. Discussion. A big problem with older motorcycles is petcock problems. The piston creates a vacuum in the cylinder above it, and this suction sucks the air in through the carburetor. Others allow it's usage. Check your fuel line routing. Buy MMG Fuel Pump Valve Petcock w/filter Scooter Moped Motorcycle 50cc 125cc 150cc GY6-0801: Fuel Filters - Amazon. Rebuilding Yamaha Vacuum Operated Fuel Valves (Petcocks. The screw holes do not line up well and requires some drilling into the tank to work. Usually vacuum petcocks fail because the diaphragm gets split and/or the vacuum line to the petcock gets disconnected or splits. With the petcock set to on, pull the top hose off the petcock, does gas spew out? That hose should be vacuum. A small point on replacement for me, is that the small inner diaphragm should probably be seated on the petcock first, so that the spring does not dislodge it from its seat, maybe preventing a seal. 7) Install one of these short hoses onto the open port of your intake manifold. Problem solved. vacuum type on 1996 model hornet 250. Please let us know if there is anything else we can do for you by contacting us by email at [email protected] , Live Chat or by phone toll-free at 1-888-339-3888. I was replacing the valve with a non-vacuum type, when I thought I would check the old one with my Mighty vac hand vac tool. Part number is 44300-19B01. Now you need some clear hose. Can anyone please tell me which is the best, the manual or the vacuum petcock? My bike was originally fitted with a vacuum but I have changed the tank and the new tank has a manual. Together, they cited information from 18 references. The sediment bowl at the bottom of the petcock is a joke in my experience. However, it wont work if the vacuum diaphragm is damaged/leaky as the vacuum will bleed off after a bit. Find many great new & used options and get the best deals for Kawasaki KZ1000 Vacuum Fuel Cock Valve Diaphragm Seal Petcock Repair Kit at the best online prices at eBay!. There's no Off because the petcock is vacuum driven, meaning if the engine isn't running, there is no vacuum, so the petcock is off, it doesn't need a setting for that. That's the job that valves do: valves are like mechanical switches that can turn pipes on and off or raise or lower the amount of fluid flowing through them. The gas flow should stop when you release the vacuum. To work efficiently, pipes need a way of regulating how much fluid can pass through them; they also need a way of switching the flow off completely. (trying to keep a straight face). To reduce your exposure, work in a well-ventilated area and with approved safety equipment, such as dust masks that are specially designed to filter out microscopic particles. If you have an air leak, the suction sucks air in through the gap between improperly joined parts instead of through the carb, which makes your fuel/air mixture more lean. These carbs are from my GL500 Silverwing, but looking at my '81 CX500 Custom, the carbs look to be identical (my CX500 also uses the vacuum-operated petcock). For this to work correctly, you need to plug the vacuum port on the carb that connected to the old vacuum petcock. OEM will work but it is a vacuum operated petcock and the diaphragm can fail causing the contents of your gas tank to be emptied into your carb and then into your engine (which is not good). 6) Cut two short lengths of the old vacuum line and plug them with a bolt that fits tightly. The raptor petcock's fuel feed tube hits the choke lever there for I can't hook up the fuel line. Part 1 Draining the Water and Drying the Water Lines. ON= main tank, vacuum controlled (normal position) RES = reserve tank, vacuum controlled PRI = main tank, vacuum bypass. One procedure you could do to help with your diagnostic quest, is to use a MityVac or similar brand, to apply and hold vacuum to the vacuum side of the automatic petcock, that should allow full fuel flow to the carburetor, at the same time place a vacuum gauge on the petcock hose ( from intake manifold) to measure manifold vacuum, then take it for a road test if it runs perfectly, then you can trace it to low vacuum or petcock requiring too much vacuum. If the carburetor is dirty and that internal port for the vacuum line is blocked it's not going to work. How to cut and modify you stock seat. You will loose the electric reserve function, but the 84/85's are cheaper the '86 electric reserve petcocks. Where is the petcock leaking? If it’s leaking through the fuel or vacuum lines it might be because the part marked #19 (Kawasaki part number 11009-1194) in the diagram below commonly fails. XJ650 Turbo models use 4 of these caps, on all four intake manifold vacuum ports. Now disconnect the fuel line that goes from the petcock to the carb. This petcock does not do a good, trustworthy job of shutting off the fuel. The big nut spins on the petcock. The lid of a pressure cooker is well sealed, and steam can escape only through and opening in the middle of the lid. How does a petcock valve work? The main purpose of a petcock is to select which tube the fuel pump will use to get fuel from the tank. Original by Mary Lou Tenney, 1987, Division of Nutritional Sciences, Cornell University. The vacuum valve does not shut off the fuel supply, and inexplicably the tap has no "OFF" position. It has at least three positions: ON, OFF, and RESERVE. You will use the plastic block and diaphragm assembly in the conversion, so take care when separating the pieces. ) I also noticed there seems to be a vacuum line going from the petcock to the #2 cylinder intake manifold and the petcock seems to have a vacuum diaphragm. The factory clamp was bottomed out-but still a leak (I did not know existed)The hose is too big to clamp down good. This is used where the space constraints do not allow the incorporation of the Automatic Vacuum Shutoff into the fuel valve itself. 2006 Kawasaki Dirt Bike KLR650. Bike runs great and no issues but I would prefer a petcock that I can actually turn off. Run both left and right fuel lines through a "T" to the vacuum valve fuel "in" port. Then when the engine starts, manifold vacuum acts on the diaphragm to OPEN the valve and allow fuel to flow. This is a petcock from a pre 2001 GS from ebay. Originally, the DRZ is a vacuum system so there is no petcock. Do you need a spare part for your car/bike, do you like to accessorize your car/bike, do you wish to give your car/bike an identity… your only online reliable destination is the one stop shop www. I have blocked off the vacuum line with a bolt so it wont be to hard to swap petcocks and hook the vacuum back up. After many attempts I could not repair the vacuum leak internal to my petcock & when parked it would always weep gas into the carb. perhaps the p/o did. The fuel filter is clean so i can only assume the next step in line to the carburetor is the vacuum petcock. It needs the engine to be running, creating a vacuum and the petcock vacuum operated section has to be working in order for the gas to flow. Follow the links XJ550H posted , as long as your petcock is not pitted inside you should be able to rebuild , takes about 20 minutes easy peasy. These petcocks are vacuum operated petcocks. When your fuel pump fails, it's pretty obvious. The anatomy of a petcock problem This is a generic description of the Suzuki vacuum-operated petcock. For instance, the 1982 Honda CM200T doesn't require a vacuum to open the reserve valve but does require vacuum to operate the valve in the 'on' position. If it sticks to the metal pieces, and it likely will, use your fingers to gently work it off. You can apply vacuum to further test the petcock and ensure the valve opens when the engine is running. Do not park it in the "Prime" position because when the float valve that closes the inlet wears out you will overfill the bowl and have fuel running into the sump just as if you left a manual petcock in the "reserve" position. 5mm fuel hose). Vacuum only operates the ON/OFF function. Proper draining. Vacuum petcock was a good idea that just did not work out. Couldn`t do that trick on my Dyna and from looking at this petcock it won`t do it either. Seat Modification by Michael Hendricks (*External Link) Driver's Backrest. My front holder is capped on both because I have no petcock on the other side, if you do, take one line to it. 4) Buy a new '84/85 vacuum petcock. One procedure you could do to help with your diagnostic quest, is to use a MityVac or similar brand, to apply and hold vacuum to the vacuum side of the automatic petcock, that should allow full fuel flow to the carburetor, at the same time place a vacuum gauge on the petcock hose ( from intake manifold) to measure manifold vacuum, then take it for a road test if it runs perfectly, then you can trace it to low vacuum or petcock requiring too much vacuum. Thanks for this - I'm about to do the same on my '79 XS650. How does a petcock valve work? The main purpose of a petcock is to select which tube the fuel pump will use to get fuel from the tank. Air enters from the outside. One way to test it all out is to put a bowl under the carb drain tube and open it up. My biggest guestion is how reserve switch work and how fuel supply is cutted off when engine is not running my bike is 3cv, i coud´nt find real pics from Haynes Manual( there were pics something vacuum lines to tank and solenoid, i have not these things only one line to pump on my bike). Prime however will drain fuel regardless of vacuum being applied. I know there is a poppet valve in the gas portion, but the check valve is to prevent the poppet valve from pulsing with the vacuum signal. tumblers and pitchers fit for any adventure. The screw holes do not line up well and requires some drilling into the tank to work. One final option is to replace a faulty stock petcock with a vacuum-style petcock which has a true "off" position instead of prime. Set petcock to the on position. In the meantime, you can add vacuum to the vacuum line and then try and plug it quickly. the petcock is vacuum operated, there should be a small hose just behind the larger fuel hose thats attached to the petcock. Ship the item to Buggy Depot within 30 days of arrival, and receive a refund or store credit minus a 7. To that end, the fuel is monitored by a sensor that measures how much is in the tank, rather than using the position of a ball bearing. To reiterate what I said in your previous thread, my personal preference is the stock petcock, it is a good quality part, and really, a tried and true design. I still have the petcock in the trunk of my PC to serve as a warning to other parts that might give me trouble. I think i will recheck my petcock filter, put in a new inline filter, check carbs for leaks, then try to clean out the black plastic splitter, put vacuum lines back to original, and then give it a ride. or was it just pulsation. KawiForums - Kawasaki Motorcycle Forums > On-Road > Concours > Fuel Tank (petcock?): Bike stalls when switching from On to Prime and/or Reserve Bike stalls when switching from On to Prime and/or Reserve. How Does a Motorcycle Work? Fuel Petcock Valve. Aux tank with quick release (QR) to the 2 in 1 out petcock. With the petcock in the stock configuration, vacuum line connected & petcock set to ON, disconnect the fuel line from the petcock & install a long section of clear tubing onto the petcock fuel port, directing it to a suitable container. Either drain the gas tank into a fuel can by or remove the tank and prop it up so that the petcock side is not submerged in gasoline, remove and disassemble the petcock. Also, you will need to block off the vacuum port on the carb with a rubber vacuum cap. you will notice it has two outlets, one is for the Vacuum pipe and one is for the Fuel Pipe, you will find that Fuel will not flow through the tap unless there is Vacuum from the Carb intake to open it, Vacuum is caused by starting or kicking the engine over to start it. From the petcock though a facet fuel filter to the inlet of the fuel pump. 2002vulcan classic original petcock has 3 hose connections-fuel,pri,and res. It is a fair bet that your vacuum line to your petcock is off. In the rebuild kit you will likely have a new set of o-rings, gaskets, a longer spring, and new piston assembly attached to your two rear gaskets. Anyone have or know where to find the details on how to convert the OEM petcock from vacuum operated to manual?. If it was a vacuum problem it wouldn't work in reserve. As soon as you turn the engine off and vacuum is lost the petcock closes. Hydration packs, water bottles, reservoirs, travel mugs. 1: How does the petcock work? Does the vacuum suck fuel into the lines or is it gravity fed and vacuum only opens the valve? 2: Will I do any harm and will the engine run if I run a line direct from the tank to the engine to bypass and test the petcock? 2: Why is the fuel filter after the petcock and not right off the fuel tank?. Usually vacuum petcocks fail because the diaphragm gets split and/or the vacuum line to the petcock gets disconnected or splits. That T connects to the other inlet of the petcock. I took this one apart because it had "no reserve". The vacuum tube coming off of cylinders 3 & 4 that run up to the pair valve split and crack open at the bottom of the tube right where they connect to the stub at the manifold. Reserve capacity will be lowered due to height of reserve gas intake height. The vacuum valve does not shut off the fuel supply, and inexplicably the tap has no "OFF" position. and thank you for the responses. you may or may not have a new spacer plate so you might have to use. Does anyone know how much pressure is used to check for coolant leaks after the thermostat has been replaced? If there is a leak, I want to know where it is before I re-install all of the intake parts. and nothing worked. I "had" like 10 manual petcocks for 1977 KZ650s at one time. Seat Modification. Kewaunee Scientific offers furniture solutions across many industries: Research, Healthcare, Government, and more. There are a number of different petcock sizes available. And of course fuel flow, at high rpm, around 5,000 rpm we have found the vacuum petcock does not pull enough vacuum to supply the fuel the motor needs to operate. With the vent port closed how does that work having it capped / is the vent port used like a fuel pump when working? Did it let air in. fix the leak because it won't open up all the way and allow full fuel flow to the carb. Instructions for OEM Petcock conversion from vacuum to manual? « on: July 05, 2010, 08:22:40 PM » I know I've seen it on here before and I thought I saved it but can't find it now. Remove the side covers. By looking at other posts, fuel should not come out unless there is a vacuum line attached and the engine is creating a vacuum.