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.
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.
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.
@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..
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.
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.
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
Excellent video. Question, I added a duel fuel carb to my B&S 420cc motor, I can get it to run , but when I turn it off and try restarting it backfires through the carb, I adjusted both exhaust and intake valves to .004, it didn’t help. So in light of what you were saying could that be a stuck intake valve or if not that, then the flywheel key. This generator is like 15 years old and was only used 1 time, so could that be causing the intake valve to stick?
@@lw1419 I would definitely look at the intake valve if it's going through the carburetor but you're saying that it runs and what I'm thinking is it might be a little bent
Thx for your quick reply. So are you saying my intake valve could be bent? If that’s the case would I have to pull the head to replace that intake valve?
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!
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.
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?
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!
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?
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.
Do you happen to have a video on how to property pull the head on a B&S motor (model 30477). I would think the procedure would be the same on most B&S motors, just provided my mod# in case it mattered. I couldn’t find one on your site nor on the internet.
Just wanted to say thank you, your info was right on, pulled the head and got the problem corrected, was hesitant about pulling the head as I’d never done something like that before, but heck it was really easy and I really learned a lot, generator is running great again. So once again thank you much.
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
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%.
Hi there from over the pond!! I am baffled, I have rebuilt a Briggs and Stratton 450 series mower. I got it started, it ran smoothly for a couple of minutes so I shut it down. When I tried starting it again. No luck. Now it is dead with it backfiring through carb. Cleaned out carb, checked the valve position and movements (lapped and reseated to be sure) checked spark, magneto and air gap all good. Checked key on flywheel, that’s fine but still nothing 😢 Any ideas or areas to check? Thanks Simon
I got a predator 212 non-hemi that’s after firing through the carburetor. I’ve been adjusting the lash every time still haven’t got it yet. Any suggestions?
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.
Ok i have a briggs and stratton on a jd z425. I just replaced the carburetor because it was spitting oil out in the gas. Now it has a intermittent but loud backfire through the carburetor. While trying wrap my head around the valve condition, I was turning the engine by hand and discovered a "hard" spot just as the intake valve on one cylinder is starting to open. I can run the mower at full throttle with it just occasionally backfiring. Is my intake valve sticking? Or is it bent? The hard spot is very consistent when turning by hand but the misfire is more irrattic.
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?
Mine was backfiring then it now it’s none stop flaming out the exhaust and it’s so loud I’m pretty sure it blew the valve to bits because there’s something rattling inside the valve cover?
I have a Kohler 21 horsepower and it won't stay running unless you keep the choke on and it backfires out the exhaust and it gets hot real quick what could cause that
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?
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?
My rider backfired on the first start up of the season and blew a hole in the muffler. Will additives for winter storage cause this? Never had any issues previously.
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...
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.
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.
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?
That's because there is a rev limiter on the motorcycle that limits it to a certain rpm (like the governor on a lawnmower engine). when the limiter engages, it slows down the rpm, however there's still extra fuel from when the engine was revving higher that is unburnt. So when the exhaust valve opens that unburnt fuel is sent out and the spark plug ignites it on its way out. This the reason you'll hear the engine pop or shoot flames. It's still back fire but its pretty normal as the engine is going from a high speed to suddenly a slower speed so that is expected.
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?
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.
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 .
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
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.
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.
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!
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
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!!!
Really good explanation, very helpful, good insight, makes sense. This might be an exception: I would think that if the timing is off or too advanced, meaning it prefires before the intake valve closes, (if that is even possible with today's smaller engines), a misfire occurs? (Comments are appreciated.)
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 😂
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 : th-cam.com/video/nAbiuEBl6Y8/w-d-xo.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.
@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
@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.
Watched your video and thanks for it. I have backfires out the exhaust and intake both. My flywheel key is good, I took the head off, cleaned it and lapped the valves. My compression went from 60 to 82. Valves did not look bent at all. Lapping looked good on both valves and head. I’m missing something. Wondering about just replacing the head and valves. This is a 420 cc champion engine.
Greetings friend, thank you for the great info! Might you be able to make a video with a hands on tutorial showing how to diagnose & clean/fix the valves that are getting stuck open/closed? Kind regards
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.
Timing key sher or partaial sher
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.
Perfect
explanation
"and ill let u kno why your wrong" I like this dude
😂😂😂😂😂😂 thanks for watching
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..
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.
Super simplified great video of explaining misfires and the cause. Great job!
Thank you
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
I have a bobcat miller welder and it’s a little small pops when running on high idle and I have fire coming out the exhaust pipe. Help 😅
That might mean the carb is flooding
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
Bro I have a riding mower you can use for a demonstration!!!! I can't get it going 😮
You in Arizona 😂😂
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
fuel mix not working not getting any air and was blockage , unblock it and run like new motor
Thankyou for this info. I will get to work on my lawnmower. High 5 from Australia !
I had a generator misfiring and after a minute died because the exhaust filter was clogged . I remove the filter and the generator worked perfect .
Excellent video. Question, I added a duel fuel carb to my B&S 420cc motor, I can get it to run , but when I turn it off and try restarting it backfires through the carb, I adjusted both exhaust and intake valves to .004, it didn’t help. So in light of what you were saying could that be a stuck intake valve or if not that, then the flywheel key. This generator is like 15 years old and was only used 1 time, so could that be causing the intake valve to stick?
@@lw1419 I would definitely look at the intake valve if it's going through the carburetor but you're saying that it runs and what I'm thinking is it might be a little bent
Thx for your quick reply. So are you saying my intake valve could be bent? If that’s the case would I have to pull the head to replace that intake valve?
@@lw1419 that is correct
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!
Good job explaining the problem and how to fix it I was up and running in no time thank you!!
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.
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?
Yeah and trapped air to
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!
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.
My 2012 Cub Cadet snowblower 528 SWE is back firing always now. What to do? Thanks in advance...
Adjust valves
Do you happen to have a video on how to property pull the head on a B&S motor (model 30477). I would think the procedure would be the same on most B&S motors, just provided my mod# in case it mattered. I couldn’t find one on your site nor on the internet.
Just wanted to say thank you, your info was right on, pulled the head and got the problem corrected, was hesitant about pulling the head as I’d never done something like that before, but heck it was really easy and I really learned a lot, generator is running great again. So once again thank you much.
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
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.
Hi there from over the pond!! I am baffled, I have rebuilt a Briggs and Stratton 450 series mower. I got it started, it ran smoothly for a couple of minutes so I shut it down. When I tried starting it again. No luck. Now it is dead with it backfiring through carb. Cleaned out carb, checked the valve position and movements (lapped and reseated to be sure) checked spark, magneto and air gap all good. Checked key on flywheel, that’s fine but still nothing 😢 Any ideas or areas to check? Thanks Simon
I got a predator 212 non-hemi that’s after firing through the carburetor. I’ve been adjusting the lash every time still haven’t got it yet. Any suggestions?
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.
Ok i have a briggs and stratton on a jd z425. I just replaced the carburetor because it was spitting oil out in the gas. Now it has a intermittent but loud backfire through the carburetor. While trying wrap my head around the valve condition, I was turning the engine by hand and discovered a "hard" spot just as the intake valve on one cylinder is starting to open. I can run the mower at full throttle with it just occasionally backfiring. Is my intake valve sticking? Or is it bent? The hard spot is very consistent when turning by hand but the misfire is more irrattic.
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.
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.
Good job explaining.
Mine was backfiring then it now it’s none stop flaming out the exhaust and it’s so loud I’m pretty sure it blew the valve to bits because there’s something rattling inside the valve cover?
I have a Kohler 21 horsepower and it won't stay running unless you keep the choke on and it backfires out the exhaust and it gets hot real quick what could cause that
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?
my autochoke on mine backfires because its to rich when I restart the mower.-*
I need to fix one of my engines that blows fire out the pipes i don't care about it back firing it just shouldn't be blowing flames out
An awesome explanation of misfire/backfire , congratulations over 1m views
Thank you 👍😊
@@RepairGang your welcome 😁
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
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?
My rider backfired on the first start up of the season and blew a hole in the muffler. Will additives for winter storage cause this? Never had any issues previously.
A valve probably got stuck open or shut
Sherd key will do it to
When sheered key what happens? The valves lose timing it's still a valve problem
Do you have videos on how to do this. I’m new to engine world. But I want to try and fix it.
I have one, it only pops after a down throttle done quickly?
Great job on the cause of the mis fire on the small engines
Thank you 👍
@@RepairGang you are welcome young man 👍😎
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
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
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.
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
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
Hell yeah thanks for this video man 👍
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
How about valve clearance samalex from zambia
My scott riding mower misfires when i am mowing.
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
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?
That's because there is a rev limiter on the motorcycle that limits it to a certain rpm (like the governor on a lawnmower engine). when the limiter engages, it slows down the rpm, however there's still extra fuel from when the engine was revving higher that is unburnt. So when the exhaust valve opens that unburnt fuel is sent out and the spark plug ignites it on its way out. This the reason you'll hear the engine pop or shoot flames. It's still back fire but its pretty normal as the engine is going from a high speed to suddenly a slower speed so that is expected.
It was the valves, I threw a valve seat. Thank you
Having that problem good information will try tks.
Iy also dorsnt seem to want to spend the driveway wheels
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
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
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
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
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
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
Great video! Thanks for making it!
Glad you liked it!
Thanks!
No problem!
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.😅
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
Can the back fire be caused by a bad coil ?
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
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 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
Pretty sure a stuck fuel solenoid on the carb bowl can do this to..
Probably
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
Thank you for the video!
Really good explanation, very helpful, good insight, makes sense. This might be an exception: I would think that if the timing is off or too advanced, meaning it prefires before the intake valve closes, (if that is even possible with today's smaller engines), a misfire occurs? (Comments are appreciated.)
Congratulations on the 1M mark!
Thank you
Off timing still means valves
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 😂
I met you irl massachusetts?
My tractor run dont have power has poping noise thru exhaust
Just the exhaust valve and check muffler make sure it's not clogged
thank you helped me greatly cheers
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!!!'
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 : th-cam.com/video/nAbiuEBl6Y8/w-d-xo.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.
Thanks for the information 👍
Thank you.
What about 2 cyl 3:29 3:30
Mine is running for about 60 seconds and the misfires through the carb
check exhaust filter maybe its clogged , happen to me .
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
Never seen that befor
@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.
Lawnmower starts, runs fine for 10-15 seconds. Then, starts backfiring and stalls. Ideas? Briggs and Stratton, 144cc E engine.
Air gap in on the carburetor to the side of the engine and a loose spring it can sometimes be a loose spark plug wire on the plug will cause that
@@Mike-su8si thank you
Watched your video and thanks for it. I have backfires out the exhaust and intake both. My flywheel key is good, I took the head off, cleaned it and lapped the valves. My compression went from 60 to 82. Valves did not look bent at all. Lapping looked good on both valves and head. I’m missing something. Wondering about just replacing the head and valves. This is a 420 cc champion engine.
it a rider club cadet
Why my petrol generator backfires
Valves
Thank you!
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
Greetings friend, thank you for the great info! Might you be able to make a video with a hands on tutorial showing how to diagnose & clean/fix the valves that are getting stuck open/closed?
Kind regards