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Agree with commenters that a clogged tank vent will produce a vacuum in the tank as fuel is consumed, resulting in starvation rather than flooding. An easy way to check the vent is to loosen the fuel cap allowing air into the tank, then tighten it and restart. If the problem is temporarily better, it's the tank vent. A bit of not well known info is: in the older type, the line will eventually press into the threads of the screws, blocking air flow. The slot on the screws is for aiding removal. If the line is replaced, PUSH the screws in, don't thread them in. This will keep the threads clear, providing a channel for air.
Love how engineers and designers make sure to incorporate so many tiny parts that you can lose when you're doing repair work on the job. They also make sure they are attached in such a way that they go flying off in some random direction never to be seen again.
We are under tremendous pressure to fulfill the ever changing government emission, recycling requirements and not appear obsolete compared to competitors. We don't get to make a lot of these design decisions. It comes from the product managers, business development teams and upper management. It is very easy to point fingers at the engineers. Our powers are limited. We do what we are told to, else we get fired and our replacements will thank us and continue to do the same.
@@HeyYall398 There can be conflict between OSHA and EPA that creates a paradox where doing the infeasible or impossible is what is expected, so the engineers are perplexed what to do to make everyone happy. Do like Volkswagen, falsify the data.
I agree with John Grossbohlin, the only purpose of the tank vent is to vent the tank so fuel can flow to the carb. I was a Stihl dealer when they had to develop a vent that stopped fumes and liquid fuel from exiting the tank via the vent. This was no easy task, as the vent had to function at extreme temperatures, not get clogged with sawdust, and operate under tank conditions of negative, positive, or no pressure in the tank. There were several variations. The fuel is not pushed to the carb by pressure in the tank, but atmospheric pressure is involved.
My 029 Super has been difficult to start after warm-up. I checked he tank vent and I bet you know already, just a bare nipple. I've ordered a new vent hose but the problem is, this saw JUST came back from the shop after I complained about getting sprinkled with fuel when cutting overhead branches. They replaced the tank filter and hose but never touched the missing vent issue. THIS VIDEO JUST HELPED ME FIX MY SAW! Thanks once again.
ive seen two problems with tank vents. first like you say the tank pressurizes and with an iffy carb will flood. the other is it not letting air in as the fuel level lowers. they slowly loose top end. those are easy just pop the cap lose for a second it will pick back up, you know its the vent.
I still use my dad's 40-year-old 028 WoodBoss, it's the best saw ever! I have only tuned it up twice in 40 years and still runs like a champ! I love your videos I learn so much. Thanks!!!
Now I always thought that a tank vent allowed air into the tank as gas is being drawn out to prevent a vacuum from being created that would stop fuel flow to the carb. In many 4 cycle engines, it's just a tiny hole in the gas cap. A bit different in some 2 cycles because of the crazy positions of operation. 🙂
LP-1200 Tygon line is what you want to resist pinching. It is also good for other uses, but is not as soft and flexible as regular fuel line. It will pull through tank grommets fine because the grommet will flex. But when trying to pull the LP-1200 type line through a rigid opening that has no grommet, the opening may need to be reamed slightly larger because the LP-1200 fuel line won't easily compress enough to make the same fit like a softer fuel line. But for replacement barb to barb connections, or through rubber bushings it is a drop in replacement.
Well I learned something today. I always thought the tank vent allowed air into the tank so it wouldn’t create a vacuum inside your tank as it was running. Thanks!!!
Tamato/ Tomato She's sharing more knowledge than U. Jealous?? or Threatened that Shes Smarter than U with Internal Combustion Engines both 2 AND 4 strokes as well as the oils and fuels..... Me I'm secure in the fact that I Do Not Know it all, heck not even close. Thats Y I can learn from these video's. Bre, KEEP UP THE GREAT INFO VIDEOS.
@@mikeholubek4419 Gee, all the man said was he learned something. You have to criticize someone for learning? Maybe you feel threatened that someone could actually learn something from a woman?
That is the primary purpose of a tank vent. A sealed container of gasoline will build vapor pressure, the equipment maker may or may not want to limit the build up of such pressure. Watched a Wranglerstar video where he mentioned Stihl had an issue with pressure building in the tank and fuel spraying out when the operator opened the gas cap to refuel. It had to be fixed for safety/fire hazard and OSHA/workplace safety requirements.
Always upbeat, humorous, and cheerful! Awesome! Also like how you have a good mic while recording making it very easy to hear and understand you so I do not have to crank my volume like I have to with some other channels I view. Always real good visual aids. You are one of the best demonstrators I have come across.
The tank vent should be allowing air into the tank so that the fuel can flow out of the tank to the carb while not letting tank fumes and fuel leak out of the vent. If the vent isn't working its like holding your finger on a straw full of soda... the fuel stays in the tank and will not flow to the carb and the saw will either bog down or not run.
More often there will be a need for releasing over pressure from gas vapors in the tank. Getting vacuum locked is a cold weather issue more often. For either problem the field remedy is simply loosen the fuel cap and let the excess pressure escape or let air enter and snug the cap down and continue working. Poulan and Husqvarna saws are airtight as a soda bottle, in reaction to EPA restrictions which are the source of the venting issue. EPA doesn't want a nanogram of fuel vapor in the atmosphere unless it involves refueling their private jets and limousines, because of course that is entirely virtuous escaping vapors.
@@artpatronforever The main reason to let pressure out of the tank is to prevent fuel from spraying out when the operator opens the gas cap to refuel a hot saw - a fire and safety hazard in the workplace. Don't underestimate vacuum locking, every gas/liquid burning motor that has a sealed gas tank has a vent to allow air to displace consumed fuel. Fuel vapors from evaporation aren't enough to displace the liquid fuel and prevent vapor lock.
@@killer2600 I have 3 Poulan Pro saws. All run pressurized.. By design they are pressure fed. All 3 spit fuel spray because CARB compliance systems are pressure captive. EPA doesn't care about safety and are only fanatics about climate alarmism. If a few loggers get burnt up EPA could not care less. 2 vintage Homelite saws have different systems definitely NOT compliant. Separate viton duckbill valves like used in purge bulbs will allow pressure relief either direction for whatever exceeds the couple of pounds pressure needed to open the slit in the duckbill valve. The viton duckbill in a purge valve is likely good for improvising a vent line termination using a purge valve under the hood in the carburetor cowling if there is room, using whatever flow direction is needed for that vent line.
@@killer2600 Yes, as Stihl learned the hard way with forest firefighters getting sprayed with gas as they went to refill their saws..... How Stihl ever recovered from that is an anomaly to me.There were at least a couple of yrs where forest firefighters did NOT buy Stihl saws. And the 'fix' was a $100 kit to re-engineer their stupid, quick fill caps.
@@artpatronforever Hate to have to argue but I have 2 Poulan made saws, they both use duckbill valves in the fuel cap and neither one vents vapor pressure out the cap - duckbill valves are one-way by design otherwise they would leak fuel.
Well my Stihl MS260 is running great. Installed a new tank vent, new air filter and a slight adjustment to the carb and it's running fantastic! Now it's on to the complete rebuild of my 2000 Stihl 046. I got it free as a box of parts when I purchased a Poulan Pro 260 and 262 for $20 for the pair. He was just happy to make a few bucks of saws he thought there destined for the landfill. I thought it anything I could strip the good parts, the clutch, maybe the chassis, bar studs, chain catcher, the engine shroud, starter and clutch cover, maybe the exhaust, pressure test the carbs and maybe rebuild them etc and trash the rest. Well in less than a week and with bare minimal parts I had both saws running beautifully and both where sold. That was 2 years ago. I still haven't touched the Stihl 046. But since I started processing my own wood left from Storm debris and trees people have cut down and need removed I started thinking the 046 would be a good saw to use with a chainsaw mill. After all I'm not processing anything larger than 12". Well at least that's the size of my planer. I guess I could cut larger and cut it down with the table saw. But I don't plan on cutting anything larger than my planer can handle really. So the 046 should be great with the mill. I just gotta rebuild it from the ground up. I'm not positive but I'm pretty sure there is a leak in the fuel tank and it may need a new chassis depending on the size of the leak. I may be able to patch it. Just not sure what will work and hold indefinitely being in constant contact with fuel add 2 cycle oil. And I'm not sure I like the idea of using an after market chassis. Anyone with any tips on how to patch a hole in a fuel tank I'm more than willing to hear what you have to say. After all a Stihl 046 that's in dependable running condition and hasn't been rebuilt with a bunch of Chinese parts has a nice resale value. I have the OEM Gasket kit order as well a several other parts such as the sprocket, carb, air filter and ignition coil. The flywheel seems to be in good condition, but I'm replacing the starter Pawls just in case. The springs look weak. I might as well replace the starter spring while I'm at it. If it's original most likely it's got plenty of wear on it to. I guess it's a good thing I started with rebuilding all those Poulans before I tackled this one. I have about 18 total rebuilds under my belt, just not a Stihl. Any tips would be appreciated.
My Poulan saw was bogging down and I went looking for the tank vent but didn't see one. However, I noticed the permanent air filter was really dirty. Cleaned it with soap and water and let it dry. Reinstalled it and the saw ran good as new. I did also clean up the spark plug since the lack of air made it run rich and fouled it up some.
Love your videos, but, a tank vent controls vacuum in all gasoline engines, a solid ( or clogged) cap would starve the engine of gas, an open vent would allow gas and fumes to leak out, almost all small engines like this use a vacuum diaphragm type vent, which is closed when the engine is off, when it is running the vacuum draws just enough air in to keep the inside of the gas tank pressure balanced with the atmospheric pressure.
First I’ve heard of a set screw inside of a vent hose. Maybe you could explain how the set screw is adjusted and when and why. Thanks ahead of time if you get to explain this.
Thanks, I really appreciate seeing this post on the tank vents. Not something I have had an issue with to date. But I had a Husqvarna that was surging and had thought to look at the tank vent. But needed to replace the carb and the ignition coil anyway so wanted to see if that was it. But as luck would have it I replaced the carb and ignition coil on a Husqvarna 141LE and a 136LE and set the High and low to 1 1/2 turns out from seated and the idle screw to just past half way in and have slowly adjusted both ways and neither will start. And I can see the fuel isn't coming up the line on one. But it has a bad split on the little blue impulse line. I went ahead and replaced the intake boots on both and I used new gaskets on the carbs. So I'm ordering new impulse lines and will be checking the fuel tank vents on both now. I have never had a chainsaw give me much problem starting after a carb, ignition coil and fuel lines being replaced. But these two are certainly doing it. Not to mention my compression gauge says everything has 30psi, even my Stihl that is a good running saw. And the gauge is brand new. But it took me 2 months to need it after I bought it and that passed their return date. And they don't warranty closeout items. So I gotta go pick up another compression gauge to. But there is plenty of resistance pulling the starter rope. And putting my thumb over the spark plug hole has plenty of pressure trying to push me thumb off the hole. So I'm guessing that's good. Just won't know for sure until I check it right. Anyway, love the videos. I'm more like the shade tree mechanic version of small engine repair and you have helped me through as number of issues when I was repairing a saw to resell and was stumped. I fell into the work by accident and needed a way to subsidize my disability check. This just fit. But it took a category 3 hurricane to show me. I will never again depend on a DeWalt 20 Volt sawzall to help get the roads clear enough to get out to check on the family and priorities I need to after a storm like that. I make sure I have 3-4 saws running good at the start of the hurricane season now and stock up on the common parts that tend to fail and a few of the ones that kind of make you scratch your head just to be sure I can keep my saws running. And I try to have a decent stock of saws that run good and I can sell fairly cheap for those people that are facing the aftermath of a storm without a saw like I did. That way they can pick up one that will help them get their property clear and maybe help clear the roads too. Always keep extra saws on hand for storm season. I'm hoping to have my Stihl 046 rebuilt and running before this one gets serious.
Used my MS170 today for the first time this summer and it was bogging so bad, I thought it was the high speed adjustment, and was about to go get a screwdriver and fiddle with it, but I said " lets try it one more time first" and it cleared itself and ran great. Going to check the tank vent tomorrow (: thanks Bre.
I would cut the vent short and push a sintered bronze filter up inside the vent tubing. They sell those filters on eBay. It's how they used to vent the tanks....easily, until they had a 'better' idea. A lot of the time they ran the vent(with the filter) to terminate in like the recoil assembly space.
On the Stihl NS250 cut the rubber vent hose about 1/2 inch from the vent cap and also somewhere on the top run of the vent tube and replace with a piece of copper tubing that is hand bent and then slip it inside the vent hose and that will not ever kink. Be sure the copper tubing fits snug into the vent hose so it will vent properly. I have done this to a vacuum line before on one of my vehicles and it worked great.
I always had this problem with Stihl. I switch decades ago no more loose bolts or bog down. I just go to the woods and cut firewood. I used Stihl from about 1980 to 87 I watch a old man come out the woods very fast with a truckload of wood. With some little Husqvarna I got real interested. I had a 028 and a 041 Stihl every truckload I would have to fix something. I went to town and bought a 50 Husqvarna in 1987 cut truck load after truck load no problem. I was thinking this is really nice. I still have that 50 and runs great.
Learn something new everyday I didn't even know they had one but that was the problem replace the hose runs like a champ thank you and yes it was missing but I cleaned it out put a new hose on it and like I said it runs like a champ now thank you
Dam, you're good! Not two hours before I saw this video I found the same problem with a pinched vent line on my MS 210. I think the tank was being pressurized so much that fuel was being pushed up around the fuel suction line grommet. I will look especially close to prevent this from happening again. I keep learning from you gal.
The vent allows air into the tank to replace the volume of fuel that has been consumed. The vent allows air in since removing the fuel generates a negative pressure in the tank. While allowing air in it prevents fuel vapor from escaping.
A swing and a miss on this one, should show removal, testing, cleaning and your solution. Also I think the tank vent lets air into the tank to prevent vacuum. Like a one way check valve. The old style tube with set screws has a little ball inside between the screws, seals one way and lets air in the other way. Most of them get lost during cleaning causing fuel to leak out a little bit but still runs fine until the tube plugs up with fine wood dust. We used to get little plastic vents that looked like a small fuel filter and just pop one in a short piece of fuel hose and problem solved!
Great job Bre, I find the newer round vents are more reliable, but need to be removed and cleaned with shop air. Have a great day. Hope the oppressive heat and humidity has lessened a bit.
The tank vent only lets air into the tank. STIHL techs always check the tank. Should hold positive pressure and allow air in to prevent a vacuum as the fuel burns.
I agree, but so many people have said the vent is to vent out pressure as well; and, I watched a youtube video that said Stihl had an issue where fuel would spray out when the operator went to refuel. A safety hazard that they had to address/fix to comply with OSHA and workplace safety requirements. A charcoal canister would allow pressure to vent out while not letting gas fumes escape. Not sure if that's what their new vent design incorporates but it seems plausible. I've seen charcoal canisters incorporated into honda outdoor power equipment engine gas caps.
I thought the tank vent let air air into the tank. The duckbill valves used in many saws let air in and not out. If the tank needs to be pressurized for the carb to work correctly then you should not be able to start and run a saw with the fuel cap off. Jusrt curious.
Have a ms250 That I had for a while. Bogged down and die on me. It start right back up and run for a few seconds and this bog again and die. After a few times it would start. First thing I thought was compression. That checked good. spark was good. So only thing left was fuel. Saw your video and soon as you said tank vent i paused the video and checked mine and noticed it was pinched in the back as you explained in your video when I Finished watching it. Fixed it and seem to run good now. Sometimes you just forget to check the silly stuff. Thank you
What to thank you for the review on the mix 2 cycle gas and oil .made a big difference. I will only use the red armor mix .your the best I watch you all the time are you help alot
Old vent allowed flow in both directions. New 'vent' allows flow into the tank only, its a one way valve, it does not release tank pressure.....which is the whole reason for its existance - to stop fuel vapour (or neat fuel) from being released into the enviroment. But of course either version of vent - if blocked - will stop the engine running right.
$0.50 cents, that same hose last Tuesday cost me $12.00 us. it's just a small piece of hose with 2 Grub screws. but I put it on and the very first pull of the starter cord it took off and ran like a new one.
Those vents, I always thought should act like a one way foot valve. It got me confused. But with a capital "B" , knowing an engineer invented it slams the door on common sense. Great video as always.
Current tank vents never let any air out, only in. They are one-way valves. If you are flooding, it is because the metering valve is not seating correctly. Tanks never develop more than 3-4psi pressure and all carburetors are designed to handle at least 7psi pressure. I own a small engine shop and specialize in Stihl equipment.
The other issue I found with my MS180 is that the spark arrestor mesh in the exhaust is clogged up with carbon. The easiest fix is to put the mesh on a tile, brick or metal plate and use the gas torch to burn the carbon deposits off.
taking something apart is easy, it's putting it back together when it can get frustrating. Like to see more demo's of putting a chainsaw back together, and see if it works.
And just for the sake of it.. im now going looking on my stihl.. Cheers chick... Theres you and one other account i follow.. and Im bloody grateful for what ive learnt... ha ha... now if only i could master the art of sharpening a chain....
In central Florida I buy saws from pawn shops. Run it till it dies then do it again shops here charge more to try to fix it than I can buy on for now I'm trying to fix it myself from the stuff you have shown got six to learn on
I have a couple of Homelite saws that are more than fifty years old and have breaker point and condenser ignition, start up first pull and still cut trees. Never have these saws seen a repair shop. They are climber saws, little one hand saws, 32 to 1 mix.
Awesome video thank you so much I bought my wife a 260 or 026 and it will start and will not rub it is bogging cannot figure out why I might know now thank you I will have to check that once again love the video thank you
Also, that little hole in your riding mower gas tank cap is there for a REASON! Ask me how I know. Fiddled with my mower once for 30 minutes until I stuck a toothpick through that hole...and fixed it.
Just to let everyone know Stihl has a new design gas vent which is behind the front pull cord cover at the top of the tank. It is a small rubber piece that fits right into the tank. Very hard to find. After time the rubber closes up. If its still pliable you can take a hot needle and open up the center. If not its about a 10 dollar part.
I WISH THOSE OLD TANK VENTS WERE STILL CHEAP , DOWN HERE THEY ARE 12.99! YALL NEED TO DO A VIDEO ON THE PULSE LINES ALSO- THOSE ARE A SUPER FUN, BUT THATS THE SECOND THING I CHECK AFTER COMPRESSION WHEN A SAW COMES IN BOGGING!
Love your videos. I have a stihl ms 200t that I didn’t think had a tank vent then looked and found where it should be, but can’t find the part anywhere 🥲
Take this with a grain of salt because I do not know a lot about small engines. But was wondering if a small copper tube could replace the rubber tube where it gets pinched. The go back to the rubber tube to attach to the breather thing. Also could that breather part be relocated before the pinching area? Anyway great tips and videos. Thank you.
Chickanic For President - Make America Garden Again... My MS250 had a bad problem with bogging down - now I know why! Cheers, Lass... would it be possible to get a dremel tool and kinda sorta notch out the plastic to give the tube just a scunch more room and not pinch?
