Why you lawn mower or generator backfires/misfires and how to fix. EASY
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- Опубліковано 5 чер 2024
- A lawn mower backfires when the air/fuel mixture in the engine's combustion chamber ignites prematurely, resulting in a small explosion. This can be caused by a variety of factors, such as a clogged air filter, a faulty spark plug, or an improper fuel-to-air ratio. Backfiring can also occur when the engine is running too rich or too lean, or when there is a problem with the ignition timing. Regular maintenance and proper usage can help prevent backfiring in lawn mowers.
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"and ill let u kno why your wrong" I like this dude
😂😂😂😂😂😂 thanks for watching
Finally, someone shares a succinct symptoms with fixes diagnosis.
I did this today and fixed my propane gen. The exhaust valve was clamped down. My gen is working great now. Thank you so much.
Super simplified great video of explaining misfires and the cause. Great job!
Thank you
Thankyou for this info. I will get to work on my lawnmower. High 5 from Australia !
good info. thanks! I believe my issue was a broken plastic cam wheel, but at least I was on the right track. The wife hit something and it started sputtering and backfiring. checked the keyway, was fine, cleaned the carb, was fine. replaced the carb. still nogo. gave it to a friend and bought a new mower, THEN started watching these vids :) told him to try a cam, but he's been sitting on it for a year now and I'm curious!
Love it, I learn better with visual writing or drawing. Saw one vid of a guy explaining the 4 points of intake, compression..... and didn't get it and ge was going to fast. Now I get it.
I'm new to small engines like this. I figured that was the problem,but thanks for clearing that up for me.
I did check the shear pin first.
Thanks for the clear, simple explanation!
this was the best how to video ever thank you
Checking flywheel key is easier then valves that would be my first step.. If you having valve issue then its only one thing to do. Take the cylinder head off, remove valves, inspect valve seats, clean everything up and lapp the valves if you have bent valve it will show you immidiately on the seat and the valve. Then don't try to straighten the valve buy new valves and lapp it in for good valve seatting area.
Congratulations on your million views I haven't got into detail yet but I picked up a 2013 Craftsman professional PGT 9000 twin cylinder it starts now that I replaced the ignition switch that was all corroded but while I don't about every minute it'll pop through the intake and then if I go to come off idle it pops really bad so I went and bought two plugs today I haven't put them in I'll get them in tomorrow and then I'll go after the valve timing unless you can think of anything else I'm also buying fuel hose because I was not getting fuel I had to spray it but once I put the ignition and I didn't spray it at all and it ran but still popped through the intake
Perfect
explanation
I just had the same problem with the back fires on my Onan p218. Found out it was the intake manifold not tightened to spec, which is 20 foot pounds. Runs smoothly now.
Great job on the cause of the mis fire on the small engines
Thank you 👍
@@RepairGang you are welcome young man 👍😎
An awesome explanation of misfire/backfire , congratulations over 1m views
Thank you 👍😊
@@RepairGang your welcome 😁
Having that problem good information will try tks.
Good job explaining.
Hi, great video btw really appreciate it. So mine starts and works just fine but backfires after i turn it off , usually a few seconds after i switch it off
Great video! A video I'd like to see is identifying engine sounds ,rod knock, valve tick,exhaust leak any other possible noises that are tell tale of certain things.
I Service quite a few mowers that the motors don't sound the best.
Good idea 💡 I will think about how to make that video
I have that problem today. 18h on a tree cutting lift, anyway it was parked a while and got water in the tank and it smells bad. Tries to start,starts but backfires. Tomorrow I'll be taking the covers off and be checking just this. Thanks and God bless you
You too friend
most excellent information... I was about to throw my mower away... got it running in less than 30 minutes... thank you.
That's super awesome 😎 I'm glad you got it running
Excellent teaching! Thank you.
thank you
Thanks for the info. I set my valves, and it's better. But it still popped when I shut it down.
It's a briggs 7 hp. Its running a bit ruff so i cleaned the carb, but maybe not good enough? But it's better. Do you think I should pull the carb off and check it again?
Thanks for posting this very informative video. I’m still having backfires and no start after adjusting valves, changing flywheel key, carburetor. Also I see air blowing out of intake when cranking. Shouldn’t intake only suck air and exhaust only expel air? Briggs and Stratton 20hp engine. Thanks!
Great explanation my man
Great video! Thanks for making it!
Glad you liked it!
Thanks for the information 👍
Great explanation for the folks just starting out. If I get a used atv that's hard to start I first check the carburetor pilot circuit and if thats good i go straight to checking valve clearence and timing of the cams. It sure makes life easier when someone takes the time to explain like this so Great video and thanks!
Thank you for the kind words
Air/fuel ratio could also cause a backfire. Basically incomplete combustion or no combustion occurs. If it’s incomplete combustion then the fuel may still be burning when the exhaust valve opens. In essence the timing is off but it’s off because the fuel is taking longer to burn than it should. That’s why you can make an engine running lean/rich run better by adjusting the timing. You’re adjusting the timing to work in conjunction with the slow combustion.
Really nice video. Thank you. Personally, I always check the flywheel key first. I find it easier/faster.
Yes but technically if flywheel is off it will make valves not time right
Yes correct
thank you helped me greatly cheers
Great explanation of mis fire and sheared key way. Congratulations on the 1M videos will always watch your videos.
Awesome, thank you!
Hi, thanks for video. But i have a question. So in my case misfiring from carb. After my repair then i tried to fix a head. I polished valves, and fix a gaps between crankshafts and valves, engine compresion now is like in new engine 12bar. Valves timeing is corect to.. So my question is or its posible that valvs are leaking and i have good compresion?
Thans.
Thank you for your details instructions! Here's what's going on with my Vanguard 23hp. I started it it revs high and slows down and pops through the exhaust. If I increase the throttle and let off it will increase rpms and stay high and slowly return. I pulled the new plugs and one side is black and the other is completely clean. Both sides have spark. I have pulled the carb and cleaned it prior because it was starting unless I put gas directly in the carb. The fuel inlet was clogged and the tubes in the carb. One side is loading up with fuel it seems. Any ideas?
great vodeo.... However, my Craftsman riding lawn mower with Kohler engine back fires when you turn it off, what would cau it to back fire after turning off the key? Thanks
Great video BUT........My mini bike engine was backfiring through the exhaust so I followed your instructions and removed the valve cover and checked to see if the valves were going up and down and they were. Then I removed the flywheel and the alignment key appeared to be fine. I figured I would just buy another engine and call it good. Then I read another thread and the problem was like mine also. "Three pulls and backfire out the exhaust." Their solution after after many different attempts ended up being the spark plug. So I replaced the plug in my engine, and to my surprise it started up and runs perfect now. So I would agree to it being valves most of the time but not 100%.
I feel that glad you got it running
If it wasn’t for your video I would have trashed the motor. Thanks for posting.
Been fighting with this issue now for weeks on a quad bike. Spins over, won't start, but backfires through the carburettor. I did a leak down test, but couldn't hear anything through the carb or exhaust. Did a wet test and it improved slightly. So I figured the rings are bad, but still should have enough compression to start. I cleaned the carburettor thoroughly with no improvement, so I bought a new carburettor, still no improvement. The only thing I can think of left to try is do a valve job on it. Would like to hear your thoughts on this one, because I could not find a valve leak when I did the leak down test.
Hey Man ❤God 🙌 Bless you.Thank Bro ;That Really works 💪 you just saved me 550$bucks man thanks again 😊
Goddam someone was about to rip you off
No That just how much a new one cost lol.😅
I enjoyed your great video. thank you
If the pop is due to the valve not fully closing, what PSI should the piston pressure be below?
For my Briggs & Stratton V-Twin 18hp horizontal shaft engine I was having pops in cylinders 1 and 2. Cylinder 1 is 150 psi and Cylinder 2 is 120 psi.
What should the piston pressure in a normal engine be in psi?
150 is very good 120 is ok
Thank you
My BadBoy 19 hp kohler engine back fires terrible when trying to start. I checked flywheel, also removed it, then put it back. Checked valves and all was good. Even removed the head and valves look great. Was going to reorder gaskets and put it back together to try it again. Don’t have a good feeling about that. WHAT ELSE COULD IT BE? Please respond. Thanks. Good video.
I got this mini bike a whether the mixture was lean or rich I still get backfire/misfire. I choked it to see if too much air was the case and it stopped was when choke was on. I didn’t do it for long either. Just enough to see if it would pop an itch didn’t. I think I am getting too much airflow from my carb. Also could be the valves and I think you’re right. The explosion sounds like it’s coming out the exhaust pipe so I think my exhaust valve might be stuck shut or open one of the two. Ugh 😑 help me brother.
Thanks!!!
Keep in mind, a bad spark plug gap will cause this exact same issue. If the gap got pushed down, this will be the same issue. Start with checking for proper gap.
Gap don't matter on small engines
@Repair Gang if you dont have a gap, it aint going to run worth a damn. I've picked up many alleyway mowers with squished gaps that just needed a little spacing, and they ran 80% better. It's definitely something that should be checked. It matters.
@@RentFree24_7 thank you for this, I just had this problem and the first thing that came to my mind is the spark plug. Mine might be bad as it has been 5 years. So i can check the gap or just get a new one.
@@RepairGangI have a brand new gravely Pro Turn 500 Mach 1 with a Kawasaki FX 921 engine. The engine has less than 4 run hours on it and it is misfiring both on startup and shut down. Is it still the valves? I know I need to take it to the dealer because it's under warranty but I'm just curious what you may think it is.
It's usually the first thing changed and I recommend you always change the sparkplugs, especially after bad gas, using starting fluid to test and backfiring, running to lean etc..
What about if you are turning off the engine by shutting the fuel supply valve and while it is spinning down it misfires/backfires from time to time? Any reason/need to fix that or just ignore it? I shut off the fuel supply to make sure the carb is empty before I put the engine back into storage for 6+ months.
thank you for great info, my problem is on my Hustler Honda 18 hp mower when I shut off engine it backfires, even when I idle down most of the time. Could the fuel shut off solenoid be doing this? keep up the awesome videos
Yes fuel shut off solenoid
Excelente
Would the flywheel 🔑 fix help with surging issues 🤔. I just opened up the valve casing and everything seems to move back and forth when pressed. I guess I can turn the blade to see if it moves smoothly. Could it also be the new fuel filter 🤔. The lawnmower started surging about 20 minutes into mowing and then 5 minutes later stopped working altogether. I replaced the filter thinking that was the issue, but now I may try running the mower without it just to see.
Flywheel could help surging would be carburetor
Great Video! My brandnew inverter generator missfires only when I turn it off, really loud, like a gunshot. Otherwise it is running fine. Not sure what to do.
It's a shut off
Briggs 190cc starts great. Once warm and upon restart it gives me one loud pop out the exhaust? Thoughts?
A little bit of gas is going into the muffler
John Deere xs75 back fires through carb some. Will only start about idle and then I have be careful not to smother it. After slowly increasing throttle it will run fine and mow. However it’s very hard to get it started. And again it will only barely start at idle after several attempts . Flywheel key is good, carb is clean, spark plug is firing and valves look like they’re functioning ok. However I had a problem a few years ago with a stuck open intake valve that I fixed with barb cleaner and elbow grease 😬. Can you suggest a fix .
Anytime you have a backfire it's the valves they need to be adjusted
The same Craftsman professional PGT 9000 one spark plugged wet one dry
Timing key sher or partaial sher
Thanks
No problem
Ok, so I did everything you said in your backfire video. Pulled the head, no problem there, including no valve guide migration. Checked the shaft key, its ok. New carburetor, backfires thru the carb, old carb did the same thing. What next? Pull the engine and check the cam and crank timing marks? I'm at a lost for this problem.
Yeah over head cam sucks it it was valves it would be intake valve
Question: let us say you live close to a Highway. You work tomorrow so you are trying to sleep. Some idiot on a motorcycle is doing 200 miles an hour. Then you hear pop pop pop. Is this the same backfiring you ate talking about that happens on Lawnmowers?
19.5 B&S. Blowback through the carb. Will not start. Valves set, new head gasket, valves lapped, valves move freely. Appears to be overlap of exhaust closing and intake opening. I know the compression release is bad. Would cam lobe wear cause this
Yes
I been trying but I can't fix the Pop sound when I try to pull start the. Bike
Question: How exactly does the flywheel control the valves? From my understanding of how this works, the flywheel does control timing but only of the spark, and not of the valves. I'm sure this could still cause backfire issues if the fuel is being ignited at the wrong time but that would be because of a spark timing issue and not a valve timing issue right?
If the key is shared, it spends the crankshaft at the wrong time
I believe you're correct. The cam controls when the valves open in relation to the position of the piston. The key controls when the spark occurs in relation to the position of the valves and the piston.
If you have a smaller battery than what is recommended in your riding mower, will this cause popping/backfiring?
No
The battery is only there to start it
Question. What if it starts right up runs fine for a minute and then starts backfiring intermittently. Sometimes it stalls out but will start right back up. The push mower runs but keeps backfiring. Thanks!
adjust the valves
I think your little inset animation of the engine was actually a 1 stroke. Good advice though.
@RepairGang I have a Craftsman LT2000 One day it wouldn't start period. Acting like no spark. Bought new coil/armature got it to run rough and lots of smoke. Messed with carb sprayed it out ran great again.. Went back out to mow a week later and it's running rough again.. Any Ideas ?? TIA
Smoke means over fill bad rings or needs a valve adjustment
Overfill? Does that mean it could be a leaking Carburetor ? @@RepairGang
@smurra3 I'm guessing overfill could mean you've overfilled the engine with oil so you're burning the extra, thus the smoke. It could also just be that the engine is running "too rich" (too much fuel in your air-fuel mixture you're burning), as that would cause it to run rough along with black smoke. If that's not it, you should check the head gasket as a bad gasket would let oil into the combustion chamber and let white smoke out of the exhaust.
I JUST REPAIRED MY NEW DUROMAX 4000. IT'S NEW BUT 300 PLUS HOURS.DID THE VALVES AND IT STARTS ON FIRST PULL.WAS POPPING OUT THE CARB.
Good job 👏👏 I love when people fix it themselves
I have a briggs and stratten mower that has been sitting idle for 2 yrs. I needed a 2nd lawnmower and decided to get it working again. There was no spark previously.
I replaced the ignition coil and there was plenty of spark, but it was backfiring bad, so I took the motor out, removed the valves and ground them to seat well. The cam was also checked and all worked well. Timing was good as were all the gears. Compression is good as well.
The carby primer pump wouldnt work and found the main jet was clogged so replaced it with a new one and then primer pump worked well. Plenty of gas going into the carby.
So put it all back together and it still backfires and wont start. Checked the spark and all good. Plenty of gas in the carby and opened the throttle, but it will not start and wants to backfire. Got me stumped on this one.
Any suggestions. Good video by the way.
I would check blade bal. if not adjust the valves something is open or closed when its not supposed to be
@@RepairGangThanks. . . I believe it is timing. . . So will go back and check again.
The 4 cylinder display (1:50) would seem to be a 2-stroke. Although the video shows an intake stroke at the start, each stroke after that shows combustion which could only be a power stroke.
Otherwise good, thanks.
fuel mix not working not getting any air and was blockage , unblock it and run like new motor
The engine I worked on today was brand new back firering threw carb only at cold start once was warm up it would stop either timing or valve sticking alil
check intake valve
@@RepairGang yea my manager ant the best with engines. that's what I told him it was
I have an old John Deere 260. She won't start. I replaced the spark plug, the fuel filter and charged the battery. First try of the spring and I had a backfire so loud my ears are ringing! Help??
Excellent explanation for the reasons for this condition and potential solutions! Thanks so much!
Suggestion - install some soft wall and ceiling coverings in this room to make your audio quality much better. The hard, flat walls are what’s causing the negative sound quality.
I get blowback out intake but no flame. Ignition fires, gas available. Spray into intake and it sputters back out.
100% you have to adjust the valves
Iy also dorsnt seem to want to spend the driveway wheels
mine was running fine then started to run rough them backfire and quit. I was running it pretty hard at the time . I get 80 compression. old briggs on a lawn vacuum. She is popping from the exhaust with starter fluid about every third pull.
dang did you fix it
15.5 single cylinder ohv briggs new head gasket valves set push rods good valves not bent and clean timing key in place but cranck no start not even a back fire has great spark but its blowing compression out the intake iam so confused 🤔 please help iam not really a small engine guy
Been 100% the valves need adjusting or one of them could be stuck. What I recommend is trying to adjust those valves even if you just got to do 10,000s with a Coke can
@@RepairGang thanks for the reply book says 3to5 on intake and 5to7 on exhaust I've tried to set the both on the tighter side and on the looser side and still no charge been fighting this thing all damn day even pulled the head back off to confirm valves are seated and they are and that open and close as they should iam about to burn it to the ground 😂
My brand new honda.pressure qashwr shots flames out when you turn it off it also backfires while in use
Valves need to be adjusted
It was the valves, I threw a valve seat. Thank you
What about a mower that pops while running? Just constant popping out of the exhaust.
Valve
Constant popping is not the valves, popping is usually caused by the engine, starving for fuel, and running to lean. Try cleaning the carburetor, you may have a partially plugged main jet.
hello to all! need help on my motorcycle, it run great the 1st 5-10 minutes ridding. and then backfire and loose of power. dose not shut down but every time I throttle backfire popping. Kawasaki KM100 what i have done is replaced spark plug. carbonator and premium gas all the time. thank you!!!
Check fuel adjustments to carburetor and that should fix it
Thank you!!! I'll give it try this afternoon @@RepairGang
Hi , My ancient 2 stroke mower backfires badly when I shut the mower down . Mower starts easy though.
Ancient probably key word 😂
@@RepairGangdo you know how I can fix it it scares the dog and the wife,
@@markward38 adjust those valves pretty simple
Is this problem worth fixing, meaning price ? It be nice to actually show and fix these problems. I like to learn.
Yes it's worth fixing i charge about 100 for a valve adjustment
Very well explained
Thanks for liking
Bought a used mower, runs great but when I turn it off it almost always backfires after the engine is almost completely shut down…and I smell gas. I’m assuming bad valves? 17h Kohler.
For that case it's either bad valves or it could be a fuel solenoid issue
What if it backfires on the exhaust when go for high speed to low speed only.
When you go from high to low speed.
That's a fuel solenoid issue or a air issue
@@RepairGang thanks m8
My tractor run dont have power has poping noise thru exhaust
Just the exhaust valve and check muffler make sure it's not clogged
Sherd key will do it to
When sheered key what happens? The valves lose timing it's still a valve problem
Pretty sure a stuck fuel solenoid on the carb bowl can do this to..
Probably
What would be the problem if it’s difficult to start most of the time after you start a fluid, and it will backfire unless the blades are engaged. This is a zero turn.
It's either your valves, your flywheel key or your timings off. You can try cleaning the carburetor that sounds pretty easy. Check your spark arrestor but if it's backfiring more than likely it's the valves
I have an opposed twin Briggs and Stratton engine that starts but runs rough and it has a new key. It is exhausting both through the mufflers as well as the carburetors (I have dual carbs on my engine). Here is a video of it running, jump to the 21 minute mark : ua-cam.com/video/nAbiuEBl6Y8/v-deo.html&ab_channel=TheShadeTreeFix-itMan I have fixed the wobbly flywheel. This was my first run since cleaning it up and putting dual carbs and dual exhaust on it. My next step is to check valve clearances. If that doesn't fix it I am wondering if the compression release could be sticking? Thanks for any suggestions. This is my first experience with an opposed twin flathead engine.
Focus!
Unless I'm mistaken, your mini-video running in the window is showing an explosion on every stroke, with no exhaust stroke, like a two-cycle engine. Kind of misleading...
Lol didn't notice that I was just putting a stock video up
my autochoke on mine backfires because its to rich when I restart the mower.-*
sheared key
Why my petrol generator backfires
Valves
"Its not the valves" crazy
Naw I'm just kidding really really great stuff here. New sub just now also and congrats on the 1 mil mile stone 🎉🎉. I couldn't resist not putting the top of this comment for the fact you killed me on your phrase "and ill tell you why your wrong"😂. Really bad day today today and that cheered me up. Thanks man❤
Edit: I forgot to ask what if it backfires out of the air intake. You might had explained it but in-between being sick and trying to get my Gen started I'm not all here atm
I mean I guess it kinda helped, without an engine to show on - it doesn't "really" help.... but nice try :)
Check out animations to see how engines work, so you have a better idea of what he's talking about
lol... 'I WANT MY MONEY BACK!!!'
lol it's 100% the valves causing you're misfire?
Meanwhile in your description you state some of the other factors known to cause misfire.
I have one that backfires after the engine shuts off for about 15 seconds then boom
That probably solenoid or carburetor issue
@@RepairGang wrong i figured it out..
My 2012 Cub Cadet snowblower 528 SWE is back firing always now. What to do? Thanks in advance...
Adjust valves
Thanks!
No problem!
Question: let us say you live close to a Highway. You work tomorrow so you are trying to sleep. Some idiot on a motorcycle is doing 200 miles an hour. Then you hear pop pop pop. Is this the same backfiring you ate talking about that happens on Lawnmowers?
No motorcycle muffler is made to pop I think
Sounds like a turbo motorcycle with an anti-lag system.