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Engine backfires but won't start.
#1
Limfe
Limfe
I have a 1 1/2 year old craftsman with a 21hp briggs and stratton gold series plus engine. It turns over perfectly, I have plenty of spark and fuel. I believe the flywheel key is sheared. My concern withthe flywheel is the plastic cooling fins. Is there a specific way to remove them to get to the flywheel?
#2
Limfe
Limfe
Flywheel is off. Used an impact wrench to remove the bolt so I wouldn"t have to wedge the fins or flywheel with anything. The pin didn't shear. Instead it craccked the top of the flywheel shaft. Any ideas on what would cause that?
#3
C
chance123
Possibly when you removed the flywheel? How exactly did you remove the flywheel itself?
After you removed the nut/bolt that holds the flywheel on, did the flywheel just lift off?
C
chance123
. Any ideas on what would cause that?
Possibly when you removed the flywheel? How exactly did you remove the flywheel itself?
After you removed the nut/bolt that holds the flywheel on, did the flywheel just lift off?
#4
Limfe
Limfe
I borrowed a flywheel puller but I didn't need to use it. The top of the flywheel was split so bad that I was able to lift the flywheel off with my hands.
#5
Rokon
Rokon
Is there a chance that when "impacting" you may have tightened the flywheel more before breaking the nut loose?
#6
C
chance123
Perhaps someone used a steel flywheel key instead of the aluminum one?
C
chance123
I borrowed a flywheel puller but I didn't need to use it. The top of the flywheel was split so bad that I was able to lift the flywheel off with my hands.
Perhaps someone used a steel flywheel key instead of the aluminum one?
#7
D
DaveTN
D
DaveTN
That took a really hard blow to split the flywheel or flywheel shaft (top of crankshaft?) like that. Could be over-tightening as aluminum won't stand up to it. Impact air gun would do it. I've seen tops of crankshafts mushroomed from hammering on them, even broken in two, but never split! On the other hand I've seen go cart racers tighten flywheels without the shear pin keys in them to advance time and they didn't crack them! Just have to get a lock washer to keep the wheel from turning. But in that case, if it did turn, what difference would it make since there is no flywheel key in it? Just re-set the timing position and try it again. I've never tried that but have friends who did.
#8
Limfe
Limfe
I called Sears and they sent out a service technician 2 weeks later. He ordered a new flywheel and key.. He said if if I waited for him to come back it would be over a week and said when the parts were delivered I could install them myself if I wanted. Seemed simple enough. Apparently when the flywheel split it may have caused internal gears to jump out of time. I removed the oil pan and realigned the marks on the cam and drive shaft gears. Engine still backfires and will not run. Someone had suggested the valve settings. After inspecting the valves I found that the exhaust valve seat was split in two and briggs waranty only covers replacement of the whole head assembly. That's fine and dandy but I would liuke to know if that broken valve seat could have set this whole fiasco into motion????
#9
Fish
Possibly so, but your messing with the engine so far would void any warranty.....
As far as the cam/gears jumping out of time, I have to throw out the red "BULL" flag, and call the whole thread "bogus"?
As far as removing the plastic fanwheel, that is obvious just by looking at it, why don't you post all of the engine's model, type, code numbers?
Fish
Fish
I called Sears and they sent out a service technician 2 weeks later. He ordered a new flywheel and key.. He said if if I waited for him to come back it would be over a week and said when the parts were delivered I could install them myself if I wanted. Seemed simple enough. Apparently when the flywheel split it may have caused internal gears to jump out of time. I removed the oil pan and realigned the marks on the cam and drive shaft gears. Engine still backfires and will not run. Someone had suggested the valve settings. After inspecting the valves I found that the exhaust valve seat was split in two and briggs waranty only covers replacement of the whole head assembly. That's fine and dandy but I would liuke to know if that broken valve seat could have set this whole fiasco into motion????
Possibly so, but your messing with the engine so far would void any warranty.....
As far as the cam/gears jumping out of time, I have to throw out the red "BULL" flag, and call the whole thread "bogus"?
As far as removing the plastic fanwheel, that is obvious just by looking at it, why don't you post all of the engine's model, type, code numbers?
Fish
#10
Limfe
The engine model number is 33187/0869 G5/111220ZA. The service tech stated to me that having me install the flywheel would not affect the warranty. Obviously the cooling fins were easily seen just by looking at it and I did not imply that any of the other issues had anything to do with it. The timing marks on the cam gear and the main gear were completely on opposite sides of each other. How or why this would happen, I have no idea. That would be why I asked on here.
Limfe
Possibly so, but your messing with the engine so far would void any warranty.....
As far as the cam/gears jumping out of time, I have to throw out the red "BULL" flag, and call the whole thread "bogus"?
As far as removing the plastic fanwheel, that is obvious just by looking at it, why don't you post all of the engine's model, type, code numbers?
Fish
The engine model number is 33187/0869 G5/111220ZA. The service tech stated to me that having me install the flywheel would not affect the warranty. Obviously the cooling fins were easily seen just by looking at it and I did not imply that any of the other issues had anything to do with it. The timing marks on the cam gear and the main gear were completely on opposite sides of each other. How or why this would happen, I have no idea. That would be why I asked on here.
#11
Fish
Fish
Looking at the top of the flywheel, it is evident that the fanwheel is held on by the two bolts. The service tech telling you that your installing/removing the flywheel would not affect the warranty is "bogus", you need to step up and "prove" that one.......
As far as you having a good running engine that all of the sudden had totally "reversed" timing marks, that is impossible to believe as well....
For us to consider this thread any farther, you might need to tell the "whole" story, if any of this tale has any credence........
Otherwise, we have better things to do.
If you fess up and are talking about an engine that you bought from someone else, and the info you provided is secondhand, well.......
As far as you having a good running engine that all of the sudden had totally "reversed" timing marks, that is impossible to believe as well....
For us to consider this thread any farther, you might need to tell the "whole" story, if any of this tale has any credence........
Otherwise, we have better things to do.
If you fess up and are talking about an engine that you bought from someone else, and the info you provided is secondhand, well.......
#12
Limfe
The Sears tech said that he believed that the flywheel was defective. The top of the flywheel itself cracked on the top. It was visible as soon as I pulled the cooling fan off.
Limfe
That took a really hard blow to split the flywheel or flywheel shaft (top of crankshaft?) like that. Could be over-tightening as aluminum won't stand up to it. Impact air gun would do it. I've seen tops of crankshafts mushroomed from hammering on them, even broken in two, but never split! On the other hand I've seen go cart racers tighten flywheels without the shear pin keys in them to advance time and they didn't crack them! Just have to get a lock washer to keep the wheel from turning. But in that case, if it did turn, what difference would it make since there is no flywheel key in it? Just re-set the timing position and try it again. I've never tried that but have friends who did.
The Sears tech said that he believed that the flywheel was defective. The top of the flywheel itself cracked on the top. It was visible as soon as I pulled the cooling fan off.
#13
Limfe
Limfe
I bought the tractor in June of 2012 from The Sears outlet store in Rome NY. It came with the factory warranty. As far as you not believing what happened, there is nothing I can do about that. The tractor was running fine, stalled, would not start up again and only backfired. The first thing I checked was the flywheel key and that was when I noticed the top of the flywheel itslef being cracked at the very top. I noticed the crack as soon as I removed the bolt. After replacing the flywheel and key, which I torqued down to the 100 lb-in per the factory specs.Looking at the top of the flywheel, it is evident that the fanwheel is held on by the two bolts. The service tech telling you that your installing/removing the flywheel would not affect the warranty is "bogus", you need to step up and "prove" that one.......
As far as you having a good running engine that all of the sudden had totally "reversed" timing marks, that is impossible to believe as well....
For us to consider this thread any farther, you might need to tell the "whole" story, if any of this tale has any credence........
Otherwise, we have better things to do.
If you fess up and are talking about an engine that you bought from someone else, and the info you provided is secondhand, well.......
#14
Fish
Nah, sorry. I am not buying any of it.
They wouldn't have allowed you to install the new flywheel, and have it covered, unless they are total morons.
And your finding the engine 180 degrees out of time.... Bogus too....... If it was running great before.........
Nah, give it up........
Fish
Fish
I bought the tractor in June of 2012 from The Sears outlet store in Rome NY. It came with the factory warranty. As far as you not believing what happened, there is nothing I can do about that. The tractor was running fine, stalled, would not start up again and only backfired. The first thing I checked was the flywheel key and that was when I noticed the top of the flywheel itslef being cracked at the very top. I noticed the crack as soon as I removed the bolt. After replacing the flywheel and key, which I torqued down to the 100 lb-in per the factory specs.
Nah, sorry. I am not buying any of it.
They wouldn't have allowed you to install the new flywheel, and have it covered, unless they are total morons.
And your finding the engine 180 degrees out of time.... Bogus too....... If it was running great before.........
Nah, give it up........
Fish
#15
Limfe
Limfe
Then I would suggest that you stop reading the thread. I came here for advice and help about my tractor not to be ridiculed by someone acting like they are on facebookNah, sorry. I am not buying any of it.
They wouldn't have allowed you to install the new flywheel, and have it covered, unless they are total morons.
And your finding the engine 180 degrees out of time.... Bogus too....... If it was running great before.........
Nah, give it up........
Fish
#16
GetTechnicalWithJd
The timing marks will only line up once in FOUR revolutions not on every revolution. Unless you knew this you would not have gotten them to line up.
I'm with Fish on this one. not possible for timing gears to jump one tooth let alone multiple.
GetTechnicalWithJd
The engine model number is 33187/0869 G5/111220ZA. The service tech stated to me that having me install the flywheel would not affect the warranty. Obviously the cooling fins were easily seen just by looking at it and I did not imply that any of the other issues had anything to do with it. The timing marks on the cam gear and the main gear were completely on opposite sides of each other. How or why this would happen, I have no idea. That would be why I asked on here.
The timing marks will only line up once in FOUR revolutions not on every revolution. Unless you knew this you would not have gotten them to line up.
I'm with Fish on this one. not possible for timing gears to jump one tooth let alone multiple.
#17
Limfe
Limfe
If the marks only line up every four revolutions then I am going to guess that the timing wasn't off and it was the exhaust valve seat causing the issue. If that was preventing the valve from closing properly would that have caused enough stress on the engine and flywheel to cause the damage? What is the correct way to set the timing using the marks on the two gears?
#18
GetTechnicalWithJd
GetTechnicalWithJd
I suspect that a piece of the seat got on top of the piston resulting in a massive impact. When this occurs the crankshaft either slows down as it absorbs the impact or stops all together. All the while the flywheel wants to keep rotating as it is storing all the kinetic energy of the engine.
This usually results in the little aluminium flywheel key sheering and very rarely, if ever, results in the flywheel or crankshaft cracking.
As a matter of interest, was it the exhaust valve seat that dropped out?
With regards to setting the valve timing, download the workshop manual for full instructions.
http://www.powerproducts.co.za/technical/briggs_276781.pdf
This usually results in the little aluminium flywheel key sheering and very rarely, if ever, results in the flywheel or crankshaft cracking.
As a matter of interest, was it the exhaust valve seat that dropped out?
With regards to setting the valve timing, download the workshop manual for full instructions.
http://www.powerproducts.co.za/technical/briggs_276781.pdf
#19
Fish
Fish
Not trying to fight, but when someone posts something that is highly improbable, I ask more questions, to try and get the full story.
When someone posts 3 or more highly improbable, if not, impossible things, I throw a flag.
I think that what is real likely is that you have been doing a whole lot of beating and pounding on this poor engine that you are not telling us about, and trying to roll all of your troubles into one nice scenario that makes it Brigg's fault.
You came here for advice/help, it is hard enough to do online when we have all of the facts {correct}, it is almost impossible if we have to devine
what info given is true or fabricated.
We offer free advice for free, so full disclosure of what really happened would be nice to have. We cannot possibly help if you don't give us the
whole story.
Fish
When someone posts 3 or more highly improbable, if not, impossible things, I throw a flag.
I think that what is real likely is that you have been doing a whole lot of beating and pounding on this poor engine that you are not telling us about, and trying to roll all of your troubles into one nice scenario that makes it Brigg's fault.
You came here for advice/help, it is hard enough to do online when we have all of the facts {correct}, it is almost impossible if we have to devine
what info given is true or fabricated.
We offer free advice for free, so full disclosure of what really happened would be nice to have. We cannot possibly help if you don't give us the
whole story.
Fish
#20
Limfe
Limfe
That is the whole story. This tractor hasn't been "beat" or neglected. I have taken very good care of it. I change the oil every 50 hours and it is kept clean and greased. The only thing that I may have screwed up on it was moving the cam gear due to my misunderstandin of how the timing marks are supposed to align. When the tractor quit I was mowing in the middle of an open 1.5 acre patch of lawn with absolutely NOTHING to come in contact with the blades or any other part of the tractor what so ever. I am not pushing blame on anyone or anything. I just asked if the broken valve seat could have caused this and if so what would have caused the valve seat to become pushed out enough to prevent the exhaust valve from retracting fully enough to close properly.Not trying to fight, but when someone posts something that is highly improbable, I ask more questions, to try and get the full story.
When someone posts 3 or more highly improbable, if not, impossible things, I throw a flag.
I think that what is real likely is that you have been doing a whole lot of beating and pounding on this poor engine that you are not telling us about, and trying to roll all of your troubles into one nice scenario that makes it Brigg's fault.
You came here for advice/help, it is hard enough to do online when we have all of the facts {correct}, it is almost impossible if we have to devine
what info given is true or fabricated.
We offer free advice for free, so full disclosure of what really happened would be nice to have. We cannot possibly help if you don't give us the
whole story.
Fish
#21
Fish
Well, my first question would have to be, did this mower work great until???
If so, please give us an idea of the timeline.
How many times have you worked on/disassembled this engine prior to this problem.
Point being, give us a detailed history of this engine.
Fish
That is the whole story. This tractor hasn't been "beat" or neglected. I have taken very good care of it. I change the oil every 50 hours and it is kept clean and greased. The only thing that I may have screwed up on it was moving the cam gear due to my misunderstandin of how the timing marks are supposed to align. When the tractor quit I was mowing in the middle of an open 1.5 acre patch of lawn with absolutely NOTHING to come in contact with the blades or any other part of the tractor what so ever. I am not pushing blame on anyone or anything. I just asked if the broken valve seat could have caused this and if so what would have caused the valve seat to become pushed out enough to prevent the exhaust valve from retracting fully enough to close properly.
Well, my first question would have to be, did this mower work great until???
If so, please give us an idea of the timeline.
How many times have you worked on/disassembled this engine prior to this problem.
Point being, give us a detailed history of this engine.
#22
Fish
So when the mower went down, no one had ever worked on it? If so who? Why?
Fish
That is the whole story. This tractor hasn't been "beat" or neglected. I have taken very good care of it. I change the oil every 50 hours and it is kept clean and greased. The only thing that I may have screwed up on it was moving the cam gear due to my misunderstandin of how the timing marks are supposed to align. When the tractor quit I was mowing in the middle of an open 1.5 acre patch of lawn with absolutely NOTHING to come in contact with the blades or any other part of the tractor what so ever. I am not pushing blame on anyone or anything. I just asked if the broken valve seat could have caused this and if so what would have caused the valve seat to become pushed out enough to prevent the exhaust valve from retracting fully enough to close properly.
So when the mower went down, no one had ever worked on it? If so who? Why?
#23
Fish
Fish
Start from the moment it started messing up, what happened right before, what you did next, etc.....