Husqvarna 235 fuel line, vent valve and plug, and bogging

530029868 plug
530026119 check valve
545078302 fuel line
I describe my journey with the Husqvarna 235 models and the final diagnosis of both units firing and bogging. Many great videos out there on how to replace the carburetor and fuel lines. I discuss the importance of using the correct size fuel line so that no gas can get onto the exterior top of the fuel tank ultimately plugging the check valve/plug.

[@stihlhead3338]

I was having the same issues with my Husqvarna 235. I ended up drilling the old vent and duck bill valve out and replaced with a piece of fuel line that fit snug in the hole and put an external fuel vent on the fuel line. The new fuel vent did not solve my idling issues. I ended up taking the intake and sealing it to the cylinder using Moto seal. I also used Moto seal between the carburetor and the intake, that seems to have made my issues 100% better. An easy way to check for air leaks around the intake is to let the saw idle and squirt a little bit of brake or carb cleaner around the intake to see if it stalls out. If your saw stalls out it means you have a serious air leak that needs to be taken care of, once you get the air leaks sealed up your saw will run a whole lot better. Thank you for the video you did a really good job.

[@FaddyMH]

The air vent should be in the cap gas tank because the location of that air vent shall accumulate the residue of the fuel oil and the wood powder, then it will be easy to maintain. I have that problem I searched a lot to find the location of that air vent I couldn't find it except with you. (Thanks for sharing) I realised that was the problem because when my chainsaw stopped and when I opened the cap the air was suced in, so in conclusion, it is better when starting to turn it on to not pump a lot of fuel so it will not exceed the carb out and then it will be reabsorbed with the wood powder.

[@davydacounsellor]

Having replaced my air vent still same issue, your idea sounds better cheers for sharing,

[@eddiemorquecho2074]

@@davydacounsellor How did you remove the Air Vent? I have the same issue.

[@davydacounsellor]

@@eddiemorquecho2074 I drilled it out, then tapered a bit of husqavarna fuel line and feed it in from the top and long nose pliers and pulled it through, it needs to be husky fuel line as it has a larger internal diameter than normal for fuel flow, then put a normal chainsaw vent on a bit fiddly but got it sorted.

[@larrymotes3512]

I have the same saw, same problem, I had guessed it was the vent, after the saw would start when I removed the fuel cap, each time it would run for a minute. Thank you great video

[@ravenshield7823]

My fuel line was dry rotted, the filter fell off, and within just one use of it off, it literally clogged the screen chock full of debris. There is a very fine screen under the diaphragm plate where the fuel line goes in. I messed with the carb the same way you did, and it would be fine one minute and bogging the next, check the screen it's easier than it looks. it's been a great saw ever since.

[@kifffrankham1689]

Thank you this was very helpful in diagnosing the problems with my own 235e.

[@peterharwood5705]

Thanks, heard about this vent but never seen any videos on it,my 235 has the same problems so i will have a look at this now i have the carb off😁

[@colinandjennytaylor1858]

Many Thanks. Your issues matched those of my 236 model (the 235, 236 and 240 appear to use the same components) Couldn't find the fuel vent, after working through ignition/carb etc., until I watched your excellent video. After clearing the vent (without removal) and a good squirt of CRC Clean-R-Carb - the saw started easily, produced more power/cutting effort with no bogging down and no longer stopped when idling. Darn stupid place to hide a fuel vent, Huh? Well done, you !

[@KianaShalix]

OMG THANK YOU!!! this has been giving me so much trouble!!!! Frustrated and wanting to smash it with a hammer so bad lol. I will clean and replace this to make it finally work!!! thank you again!!!

[@Kevin-jd1rm]

Great video, and a big help, Thanks. it covers a subject that does not have much presence online. A blocked vent / duckbill creates vacuum in the fuel tank , when using a vacuum pump for diagnosis I do believe that the vent is supposed to be only a small leak , only lets enough air in to replace the space created when fuel is used and yet keep gas fumes in the tank. So the testing pump will still be able to create a vacuum but will leak down slowly. Mine was plugged on a new saw, neothec husky 365 clone. The screen had what looked like orange paint overspray on it. When the saw was hot and shut off I could hear a slight "whistle" the air getting sucked in through the screen believe it or not.

[@FaddyMH]

The air vent should be in the cap gas tank because the location of that air vent shall accumulate the residue of the fuel oil and the wood powder, then it will be easy to maintain. I have that problem I searched a lot to find the location of that air vent I couldn't find it except with you. (Thanks for sharing) I realised that was the problem because when my chainsaw stopped and when I opened the cap the air was suced in, so in conclusion, it is better when starting to turn it on to not pump a lot of fuel so it will not exceed the carb out and then it will be reabsorbed with the wood powder.

[@bangerseamen]

Thanks for this. Most useful knowledge.

[@HOTRhuntinontherock]

Great video!!!, after seeing this I decided to take the top hose off the primer which connects to the tank next to the vent that you perfectly explained, and that solved the issue for me so far, I don't need the primer anyway, the choke is good enough. So I'm using the primer hose now as a vent.

[@tessiehuskey1]

Very good explanation on the video

[@THC11]

Excellent Video My Friend , Darn tank vent.

[@larrysairlines6185]

Some man!! I’m trying this tomorrow!!

[@StagArmslower]

I have Husqvarna 240 and I drilled the golden screen and replaced it with small fitting glued with JB Weld. I connected the tubing to a small check valve from Amazon. It works great now although I didn't have luck with aftermarket carburetor and had to buy original Zama carb. Et the end of the tubing I installed weighted air filter from my RC supply to protect the check valve from small debris

[@duckkitten9243]

Hey there. Sorry to bug you but I have my 240 completely torn apart and I want to follow your approach to redo the vent. I removed the golden (pain in the ass) plug. What type of tubing did you use and can you provide the link to the check valve you bought. THanks.

[@4xprops457]

Thank you! Great information!!!!

[@NinoSutton]

Well done sir!

[@TgWags69]

I never left a comment after Isaw this a month ago, but thanks so much for this video. My saw has been pretty much dead for 10 years after only using a few times. The vent was absolutely plugged full of oily sawdust. Had so many people work on it trying to fix it and it just would never run and bogged down like you describe. I made a tube out of air cleaner felt and super glued it in the corner over the vent and sqeezed the top closed to make a felt cap about an inch long. This helps to provide enough breathing room that it doesn't clog back up, just like the air filter on the carb. Anyway, runs great after so many years taunting me about the wasted money I spent buying it and time and money wasted trying to fix it. Thanks again 😉👍

[@10mmsocket32]

Glad to hear it helped you out. Thank you for leaving a comment.

[@jamesfarley5183]

chainsaws work in the worst conditions ..sawdust mixes w bar oil vapor/droplets and blown into/ over and around every part of saw.

[@seahorseist]

Excellent many thanks

[@jerrysoutherland662]

You can use a small screw,and screw it in the screen and pull the screen out and the duck bill valve will be under the screen,pull the duckbill out and replace both of them.

[@stihlhead3338]

The vent on mine was not a screen, you would never get a screw through this vent. I had to drill all the way through and then use a screw, and the duck bill is directly under the vent like you said.

[@philliphall5198]

It’s solid like a old style fuel filter

[@ShoshonSun]

Great video! I had this exact problem with a Stihl, it would run perfect for a few minutes, and then slowly die; it wasn't the carb adjustments at all, it was the gas tank vent! If you can show the removal of the vent and also the removal of the vent and the replacement of the vent itself that would be awesome!! I have not seen a good video focused on the identification, repair, and replacement of the gas tank vent itself! Thanks again!!

[@10mmsocket32]

Thank you! If I come across a saw that needs the vent replaced, I will create a video of it.

[@Sensei948]

@@10mmsocket32 Master, can 33: 1 ls + in the 545rx brushcutter be harmful?

[@10mmsocket32]

@@Sensei948 no clue whatsoever. Sorry. Please use your saw according to your users manual.

[@frankrosenthal1586]

I have noticed that when I remove the gas cap there seems to be a sucking sound of air. Probably caused by vent not working. Thanks for this video.

[@grantfryer407]

yes there's a similar model it's my 236 same probs reckon..im thinking of drilling a tiny hole in fuel cap or alongside the air plug you showed to let the pooled fuel out...

[@leebrech9616]

Thanks Bro. I have a Husqvarna 240 x-torque that has been driving me crazy doing the same thing. Has been taken to 2 shops and still does same thing. I was going to look for problem myself and thanks to you I know what is happening.

[@jameslenthall6008]

thanks dude

[@stephenjackman6163]

There is a sintered bronze filter as seen in the video, HOWEVER mounted under the filter at issue, there is a “duckbill” valve. This valve allows air from the outside into the tank, BUT it will not work in reverse. Otherwise you couldn’t prime the carburetor. And gas would leak out.

[@10mmsocket32]

Correct! In the video I explain that any gas over the “bronze filter” will interfere with the duckbill valve from allowing the outside air into the tank.

[@garymcburnett4570]

thanks man hv same problem maybe it will work for me

[@lobdsk]

OMG!!!! This exact thing happened to me wish the fcuk I saw this video first would have saved me so much time energy and money.

[@tonyd6821]

I need help ....I just bought an Husqvarna chainsaw 326 it started when the fellow tested it but the day after only enjoyed for fifteen minute then it become a night mare . (long story short ) I replaced the carburettor ---new one from China --- replaced it but stil didn't start and because it hard to pull the rope i decided to have a look the piston.... it shoes a little scratch on the front --muffler-- has not damaged the ring and the cylinder ...then I tested the ring in the cylinder for any major gap It does have a gup of about one millimetre is that ok or I have to replace the ring and the piston ? Thank you

[@tlough1]

Man great video. I have one of these saws in my shop. Will try to start, but will not idle. When I pull the trigger, it tries to run but bogs down and stops. I drained fuel, saw that the fuel filter was broken off the end of the fuel line inside the tank, and the fuel line was yellowed and brittle so I ordered the oem from Husqvarna and changed. Checked carb diaphragms and they are still flexible so I put back together and same result. I’m wondering if I have the same issue. The saw will start, but will not idle and will only run if I give gas on the trigger, which sounds like fuel starts to get through but then a vacuum gets created due to blocked vent. I do have one question for you, when you replaced the tank fuel line, where did you get it from? I may have missed it in the video. Thanks again!

[@RoryTrackrod]

I saw a video, years ago, where the owner drilled out the vent and glued in a length of pipe and stuck a valve on the end so that it wouldn't block. I also have the fuel supply problem and have come to the same conclusion as you. Just to make matters worse, I have what feels like hydraulic lock, when I pull start it. I am now on my 4th pull start assembly, as the cog gets chewed up. Luckily I have 2 other saws I can rely on..

[@10mmsocket32]

Very sorry to hear. I am still having problems with one of these two saws. It’s been nightmare of an experience working on them but I have not given up.

[@RoryTrackrod]

@@10mmsocket32 My 4th pull start arrived from China and unlike the others it had a recoil spring assembly in it. This cured the locking when pulling to start, but the fuel starvation after a few minutes remains, so my next job is to pull the tank vent. Fortunately my Chinese 52cc and Stihl 180 are faultless, so I'm in no hurry..

[@jamesfarley5183]

any saw w over 120 lbs compression will feel like hyd. lock due to short travel of piston. the " pull harder and faster" is hard on plastic gears due to short severe engagement. better to learn the choke styles ie full on/full off, full on/half on ,primer/ no primer choke carb fill. starts.

[@Drottninggatan2017]

I notice that you have the fuel lines from the primer bulb hooked up backwards. The shorter connection on the bulb is supposed to suck fuel from the carburettor, and the longer connection is the return back into the tank. In this way you will be pushing fuel and / or air into the carburettor, and that might find its way to the outside. Many people are having problems with these saws, the Husqvarna 235 and 240. With these symptoms. There is a video with a guy who fixed a hidden jet under the throttle shaft on these carburettors, and that cured the problems.

[@10mmsocket32]

It has been some time since I looked at this saw and worked on it. I will have to go back and see if the lines are incorrect. Thank you for bringing this to my attention. Any chance you could give me some info (title, name of KZbinr) about the video you mentioned?

[@Drottninggatan2017]

@@10mmsocket32 At 10 min into this video he is removing the jet. Appears to be in greek. Perhaps you can ask him what he is doing. kzbin.info/www/bejne/m4eZZpuLrreFd7s

[@ArkatSaick]

I also have 235 chainsaw,but it has problem with sparkplug. When i try to start the engine, the spark will get wet,or oil.how can i fix it.?

[@flutetubamorg]

On my 345, the bulb primer return attaches back to the vent

[@keithkuhn6404]

Where does that check plug (duck bill, small one way check) go? I could not get the vent out so I am hoping that just cleaning it is enough. Good video thanks. I can't get the new fuel line pick up (left side) in through the hole. Any suggestions? Once again thanks.

[@10mmsocket32]

I had bought OEM fuel line for my saw which was the perfect size for that hole and it was also cut at an angle on one end and so it was easy to push through the hole into the tank. You can rub two cycle oil on the outside of your fuel line to lubricate it and could also use long needle nose pliers (a 45 degree needle nose pliers helps tremendously in these situations).

[@jamesfarley5183]

any line going into a tank must be at least a snug stretch fit to seal the gas from leaking.

[@chainsawFirewood89]

Man its 330 am im still trying to get my Fuel live from the right of the Tank Nd i got everything hooked but having difficulty getting the fuel line that gose fro the tabk yo the Bubble!

[@keithkuhn6404]

Just one follow up. I found the check plug vacuum (duck bill) one way check in the gas tank. Don't fully understand how it got there, but I know it goes on the bottom of the vacuum filter. So I have to remove the small round vacuum filter and replace it. I will have to order both duck bill and filter, but I can't get the filter out. Do I have to destroy filter to get it out? Does it screw in or just pry out?

[@jamesfarley5183]

filter is a porus solid filter clogged by dust/gas vapor .must be repaced to allow duckbill to work. can't clean well as carb, cleaner/ethanol swells it.

[@jamesfarley5183]

swells the duckbill valve.

[@jamesfarley5183]

drill small hole in center ,screw small wood screw in and pry out then discard.

[@johnb5519]

Those duckbill valves are prone to loosing their elasticity over time. The only option is to replace them. They really are a cheap solution to a more complex valve system that would cost the manufacturers a lot more time and money to make. The amount of air venting into the tank, can't be less than what the pump in the carburetor requires in vacuum, to pull the fuel. I have been looking for the original valve for my old pioneer saw, with no luck so far. It's called a combination umbrella duckbill valve. It lets air in, but in case of heat expansion built up in the tank, the umbrella part of the valve is forced up, to release the pressure. So I have been trying to make a mechanical valve to accomplish this, but the complexity required is equivalent to a needle and seat arrangement, or a spring loaded ball type valve. No luck so far.

[@10mmsocket32]

I may have to replace the duckbill valves. Wishing you all the luck on repairing your saw.

[@jamesfarley5183]

echo trimmers use a remote vent valve that connects to a hose which can adapt to a hole w stretch fit and plastic / metal reducers. easily replaced/obtained and durable.

[@johnb5519]

@@jamesfarley5183 Thanks James, I'll look into that.

[@jamesfarley5183]

usually pressure in a tank is not too much a problem as excess pushes the carb.needle open to dump excess pressure into engine. vaccum is the main problem.

[@johnb5519]

@@jamesfarley5183 Yeah, my main problem is without the valve, when you tip the saw for horizontal cutting, fuel comes out.

[@philliphall5198]

It’s best to have 2/3 extra vents and try to keep saw clean Dry wood and duel chains will stop it up quickly

[@GertTown]

I have an old rancher 455. Do you have to take them all apart to change the fuel lines?

[@10mmsocket32]

I am not familiar with that saw. Sorry I can’t be help.

[@jimforsyth2.]

Dose anyone have part numbers for the replacement of a link

[@robjones9811]

same problem on a 236x tork

[@dannybuchanan9516]

Would the loose fitting gas line not have vented the gas tank even when the vent was not allowing air in??

[@10mmsocket32]

I would say that’s possible but the little gas anywhere is going to seal or partially seal around the line (similar to the top of the vent).

[@matteomcmillan2595]

If I get gunk in my fuel lines can I just spray it out with carb cleaner ????

[@jamesfarley5183]

never works well as carb cleaner swells hose/ needle valve and loosened trash is pushed into carb. replace lines as trash sticks to inside of line well.

[@jerryfuqua3781]

I have same problem with my 240,but after changing my lines my vent is leaking gas when I pump the primer bulb. It is pushing the gas up through the vent. any suggestions?

[@10mmsocket32]

Is the duckbill valve missing? My other guess is that your fuel lines are incorrectly connected. You shouldn’t be pressurizing the tank.

[@Lion-cf3jk]

So you suggest to change the carburator right

[@10mmsocket32]

Not at all

[@patcotsman866]

Goes to show how perserverance is usually rewarded. if misery loves company,, I had a 63 Ford radio which would stop then start working. Pulled the radio to eventually find what I couldn't happen---an adjustable mica trimmer capacitor with an intermittent partial short. Unbelievably I found a customer of mine who had the same trouble on a Chrysler product. This is boring to most, but I figured I'd show how frustration "may" lead to a good result. Thanks much.

[@stihlhead3338]

The problem with the Husqvarna 235 has nothing to do with the fuel tank vent, and has everything to do with the carburetor. Fuel bulb is called a purge bulb not a primer bulb. Purge bulb has only one use, it supposed to purge the air bubbles out of the carburetor and fuel lines. A primer bulb is used on lawnmowers, and pumps fuel directly int the venturi. If fuel is puddling up under the carburetor from pumping the purge bulb the carburetor has a defective check valve. You should be able to pump a purge bulb all day long and never leak one drop of fuel. Husqvarna would never admit that the zama C1T-W33c carburetor is a defective design and should of been recalled from day one. Actually the tank vent was designed to be under the carburetor for the reason of recycling any unspent fuel back into the fuel tank to meet EPA standards. Now most saws have a fuel line directly from the tank vent either back into the fuel tank or into carburetor air filter box. The best way to remedy the ongoing issues o bogging with the Husqvarna 235 would be to find an aftermarket carburetor and throw that Zama carburetor in the scrap bin where it belongs! I would bet that shortly after this video that the bogging issues surfaced again. I would really like to see an update to this fix to see how long it lasted. I refuse to work the Husqvarna 235 anymore, I always recommend to anyone that wants me to work on a 235 to cut your losses and scrap the saw and not try to sell it to someone and have the same issues.

[@Lion-cf3jk]

Like a chainsaw is the best agresive cut and everything but these are big problems

[@jerryfuqua3781]

Duckbill is missing. how do you replace it?

[@10mmsocket32]

Not sure on that one. Maybe just place it back on where the valve goes? Use long needle nose plier?

[@octaviandobre9712]

hello on the return line there is a nipple what for is

[@10mmsocket32]

Inside the tank, I don’t believe there is a nipple on the two fuel lines. One fuel line will have the fuel filter and the other will be an open fuel line.

[@jamesfarley5183]

just a fitting to keep stretched hose from coming out on return line.

[@shawncarter4242]

One I have will start for like 10 secs then just shut off

[@marcfiore4319]

Brilliant bit of troubleshooting, but this could have been a 5 minute video if you’d planned what you were going to say in advance. This wasn’t a murder mystery, no need to drag it out!

[@Aerocruz22]

I'm sure that's my problem

[@stickshaker101]

You should really change the name of your channel, it's almost impossible to find!

[@10mmsocket32]

😂

[@txboyd75]

😜😜😜😂😂😂😂

[@stuartmcmillan8042]

Yes after removing the fuel cap you could tell there was vacuum now wheres the vent i'll google it ah ha .

[@ainodekam3785]

This is the most nasty full of issues chainsaw from Husqvarna but I think the most important isue is the carburetor which is made by zamma China if you buy a new one original not aftermarket it will run better a period of time after that it will have the same problem.I think that the big problem is carburator.

[@noelpeterson5591]

Husqvarna are a crappy plastic saw.

[@rodneyfields4081]

Absolute pos, I will never buy another peice of equipment from Husqvarna in my life, I regret not getting a Stihl. Live and learn I guess.

[@chicken_permission]

The problem is that you bought a cheap husky any husky in the three series or higher without do any still for reliability any day

[@davidrobitaille3558]

Worst video ever, you did not fix anything nor point anyone in the right direction.

[@markadolphus5094]

Great video 😊This is a big problem! I don't know why Husqvarna have not shared information about tank/vent/pressure requirements ??? I have done everything to Mt 562xp auto-tune and it still won't go.... prob wasted money on a new carb as I first thougt that was my prob inspected that vent, cleaned it, broke it, bought and waited for a useless defective clone product. Have endlessly searched for a legit on. Made my own even... but i😊 still have no idea what the f*** I'm doing it still won't turn up properly if I manage to start it