I had an issue like that with my standby generator , ended up being a sticky exhaust valve . I used SEA FOAM spray and it unstuck the valve . Was an easy cheap fix . Hopefully it's something easy to fix for you , however after watching your videos you're amazing and YOU GOT THIS .
The valve guides on those Briggs V-Twins have a known issue with moving inside the head. Ultimately the valve loses the ability to move properly and the push rod eventually comes off and slides into the sump. I have one of these and it happened to me. I was fortunate enough to find a used head and replaced it.
A friend of mine was a lawnmower shop mechanic. He was driving a riding mower onto the lift to do deck work. He heard a "tink" over the sound of the engine. He said he knew right then that what happened, the compression release failed on a Briggs single cylinder engine. He turned it off and tried to restart. The engine couldn't get past the compression, classic symptom of a failed compression release. He had to explain that to the customer. Thankfully the customer was understanding.
I was in the auto repair business for 41 yrs. It happened on autos more than I care to count. I would invite them to come see the auto and discuss it. That always seemed to help.
i had that problem with my mower, loaded it on my trailer running great, got to my lot out in the country to mow it and it would not start and was popping. ended up being the float stuck open (guessing from hitting bumps on the road), took float bowl off and cleaned it and get the needle and float unstuck and it fired right up and has been running great since.
Absolutely correct Dony after you get the valve cover off the suspected cylinder and it could be both break out the old trustee, smart phone, and capture a few pics not to mention maybe even a short video clip. The good old adage a picture/video is worth 1000 words. Once the valve operation has been determined good/bad the Avenue to diagnosing becomes that much easier.
Great tip about the customer. I would check to see if the nut came loose on the valve bolt. I have worked a lawnmower that the adjusting nut for the valve was tight, but the main bolt was loose. If not, a compression test than a leak down test.
My vote would probably be here only because I've ran into this a few times with that very engine. The older craftsman had the kohler pro twins and they never had any issues
When I get something like this (I do farm machinery, tractors and such but it's the same perspective from the customer's point of view) I take a video, show it to the customer, and ask flat out, "... is this what it's doing for you". That verifies two points; One, is this the problem you are paying me to fix? and Two, this is what I found at the very first instant I inspected it. Only issue this might present is that you must make the time to get back to the customer ASAP. But, it's a better situation than, "... it ran better when I gave it to you."
I had a similar problem with a Kawasaki engine on a John Deere tractor. Rodents had packed grass clippings and leaves around the head. When the engine was operated the clippings and leaves blocked air flow around the head. The engine got so hot that one of the valve seats popped out. Once repaired the engine ran fine.
Really common where I live, people don't take care of anything, even if its theirs....then they expect a repair shop to fix everything for little to nothing, and will cheap ass their way out of the repairs as well, or blame you for the problems they caused themselves from simple lack of routine maintenance.
Hi, yes that does happen, and as you say, it makes it hard when it started and ran before. A good call , contact the customer soon as you know what is wrong with it. Good video thanks.
I had a Z-turn every time you would move it, it would start. Then you would go to mow with it, and it would quit. This mower drove me batty trying to figure out what was wrong. One day I took the battery out and I just happened to see a loose ground wire and all I had to do was resolder it to the connector. when you would move it, it would ground out to the frame and start, but using the mower the wire would Jiggle around land on a dirty part of the frame, lose ground, and quit. Aggravating, to say the least.
I had one that would not start on a kohler single courage. The valve lash on the intake valve was almost zero meaning less than .001" It would not start and kept backfiring through the carb etc. After adjusting the intake lash to .004", it fired right up. The no-start condition was after doing a full tune up.
I have a similar Craftsman that has this popping problem that came up suddenly. I thought it had a bad coil so I replaced both coils but still doing the same thing. Next I was planning on checking the overhead valves and pushrods. My guess is pushrod is bend or popped out of seat or the cam went bad. I'll be watching to see what you find and I hope it's an easy fix! Good Luck Donyboy73!
A lot of times, when people do not service their equipment or do it properly, what happens is the valves lash gets so bad that the push comes off the rocker arm.
It has probably been overheated due to lack of air flow and slipped a valve guide. I've had them slide in and out, one time runs like crap, next time may run ok.
What is that knob selector thing by the operator's left foot position at 1:20 Donny? I think it overheated every time he used it from all that stuff in the cooling fins for years and driving it up the ramp at a 45 degree angle finally shook a crack in the head enough to separate it.
My thoughts as well....and asking the customer doesn't get any truthful answers usually either....they wanted someone to come pick it up so they have someone to blame for the problem they know about but didn't say anything about. This is why I don't work on stuff for people, way too many liars out there looking for their next handout in free repairs.
I'd say it is the debris on the heads , overheating the cylinders, and this rears the ugly head of a B&S valve guide problem. The valve guides on the exhaust move up blocking the valve from going back down . This usually lets a push rod fall out from under the tappit. Briggs does not sell replacement guides , you have to purchase new head assemblys . That's my guess as to the problem . 😊
It looks like a B&S V-Twin. Notorious for carbon buildup causing the exhaust valve to stick and dislocate the valve guide. Correct fuel mixture along with using Marvel Mystery Oil in the oil and SeaFoam in the gas will keep that from happening. But last one I fixed I had to pull the guide out clean everything and put it back with Loctite cylindrical part bonding compound. I didn’t have any special guide installation tools but if I did I would have still used it.
Engine overheated due to insufficient air flow across cylinders, caused by that grass buildup and/or mouse nest. Valve hung up, lash is way off, dropped valve seat, head gasket blew?
Hey dude I bet it has been a while sense you have worked on it, a bought a new carb for my 5Hp Briggs like the one on your old tiller, and it came with fuel filters but I don’t understand where they go as the carb sucks it up so I don’t know where to install them
My guess is fuel. Low on fuel with water on the bottom of the tank. Got mixed on the trailer ride. The tilt on the ramp, gravity fed. Betting all that fuel eventually getting to the carb is largely water.
it can happen that once the engine cools the damage surfaces. The damage could already be done because the temp is the highest after you shut it off because the air vanes on the flywheel have stopped cooling
Assuming it has spark, I agree with others that it's a valve problem... either: 1) Overheated and guide slipped 2) Overheated and caused a problem with any plastic parts on camshaft 3) Overheated and valve lash got out of whack Otherwise, it blew a head gasket. But, i would think it would still try to fire on one cylinder if it had spark? Very interesting!
Started snowblower on the truck on a cold day. Put throttle down to idle to warm up. I was about to back it down the ramps. Before I put it in gear the connecting rod went through the block... Oil just poured out If my son had done the same I would have said he left the idle too high with no load on the engine.
Really? I have the 25 hp in my 2006 J.D. 155C which now has about 850 hrs on it. Still has original plugs and has never had any work done to it. Change oil/filter about every 125 hrs, on it's on it's 3-4th air filter and runs great. I'm well aware of the valve guides overheating so make sure there is no mouse nest in it every spring and had the shroud off about 5 times to blow everything clean especially the guides. I haven't even adjusted the valves on it yet and no smoke or oil usage. This sure hasn't been babied here on the farm but I always let it warm up before mowing and let it idle a few minutes before shutting it off. Certainly not one of Briggs best but not junk.
@@jefffrayer8238 correctly maintained you can see a good life, provided you don’t have one with a defective cam. Keeping the fins free of debris has a lot to do with longevity along with proper oil changes.
Twins will run on one cylinder so it most likely a two cylinder issue, could be bad diodes ( no fire) or bad cam shaft ( slipped lobes). Not a gravity feed fuel system so I don’t think it would have flooded on the drive to the shop.
In all fairness to both parties, the opposite could also happen where the machine was running fine but the next day it failed for the customer. It was working when it left your shop! The trust needs to go both ways and good customers and shops know this.
One question, did you see the customer start the machine cold or was it already running. I got a mower and the customer started it and I could restart it but back home I couldn't. After I thought about it they primed it with spray before they started it. So it would not prime or start at my place.
"No, it was running great Don....I just wanted the oil changed and the belts checked"....the usual curse of "the drive off the trailer or through the garage door" and all the demons appear out of nowhere or disappear completely
Either the customer is not being truthful or it is a very rare case of something giving out at a very inopportune time! Rare like hitting a straight flush in poker!
Your first sentence is the correct answer in many cases....customers are always looking for a way to place the blame onto someone else when they have a problem with their equipment....even on a regular service, never just assume the customer is right about what is wrong, or what needs done....do a full inspection on the equipment even a video/photos of before/after might be quite useful in proof of the state of the equipment when you received it.
What’s troubling is the fact that it’s a twin and it won’t at least run on one cylinder. Usually,even with a rodent infestation making it overheat,the valve guide moving, and bending a pushrod they will still run on one cylinder. I think that the camshaft gear failed.
I'm not sure about a blown head gasket, cause it would need to blow out both, cause it would start with one blown head gasket, it would just sound awful... Popping .... So I'm thinking, no spark cause of bad diode, even no compression, maybe blown head gasket on one side, and out of place valve guide or valve seat.
Well, 1 way it can be avoided is to have a symptom sheet list when picking up any thing. Have the customer fill out name, address, type of mower, new date, bought new or used, gift, bla, bla, bla, you know what to ask, just building a list by them. Then list, things like last service date, by who, ethanol gas or treated gas, you know the list to make of thing's to list. Its what you normally find in your area. What your doing is have a before list by the customer. Your drawing a line in the sand. Just something that builds a list of to protect yourself. We know what happened has nothing to do with us, "*:it happens!" This is a buffer when you call and say, "has the engine been starting okay?" Customer says, "well sometimes no, sometimes yes." Well it won't start to get off the trailer, I'll get it inside and let you know in the morning what I find Mr/Ms Mann. This sheet can be long, longer the better, just make it easy on them by multiple choice answers, have words for answers they can just circle, draw a line thru, check mark, you know how to do this, make it easy for them, if they knew how to fix it, they would have instead calling us. Take your experience and make your list. I'll be starting my repair business in the fall/winter/spring by word of mouth. I'll have a list for them to fill out on a clipboard. They are preparing themselves for a diagnosis from doing nothing to the mower for how long and your just correcting their mistakes for lack of maintenance. Like I said, if they knew what to do, they would have.
Don't expect to get much use out of that list as when something goes wrong with any equipment, the customer is always looking for someone else to blame...list sounds great, but in reality it won't do you any good when the customers are not forthcoming with useful information....
It seems like something in the valvetrain. Maybe out of time, bent valve of valve lash issue, broken cam, broken compression relief? Sorry I know that's a lot. 😂
Can you guess what the problem will be? Please comment below and find out tomorrow morning!🤔
Chuck valve clearence, and clean out the mine nest
Needs new plugs 😊
I think valve got stuck at open position.
Overheated due to nesting material and then either blew the head gasket, cracked the head, or caused valve/valve guide/pushrod issues.
Briggs engine. Overheated cylinder and dropped a valve guide
Just the fact that the guy called you up to pick up his tractor, mean he had a problem with it. Thanks Dony for the video and may God bless you Sir.
I had an issue like that with my standby generator , ended up being a sticky exhaust valve . I used SEA FOAM spray and it unstuck the valve . Was an easy cheap fix . Hopefully it's something easy to fix for you , however after watching your videos you're amazing and YOU GOT THIS .
The valve guides on those Briggs V-Twins have a known issue with moving inside the head. Ultimately the valve loses the ability to move properly and the push rod eventually comes off and slides into the sump. I have one of these and it happened to me. I was fortunate enough to find a used head and replaced it.
A friend of mine was a lawnmower shop mechanic. He was driving a riding mower onto the lift to do deck work. He heard a "tink" over the sound of the engine. He said he knew right then that what happened, the compression release failed on a Briggs single cylinder engine. He turned it off and tried to restart. The engine couldn't get past the compression, classic symptom of a failed compression release. He had to explain that to the customer. Thankfully the customer was understanding.
I was in the auto repair business for 41 yrs. It happened on autos more than I care to count. I would invite them to come see the auto and discuss it. That always seemed to help.
i had that problem with my mower, loaded it on my trailer running great, got to my lot out in the country to mow it and it would not start and was popping. ended up being the float stuck open (guessing from hitting bumps on the road), took float bowl off and cleaned it and get the needle and float unstuck and it fired right up and has been running great since.
Absolutely correct Dony after you get the valve cover off the suspected cylinder and it could be both break out the old trustee, smart phone, and capture a few pics not to mention maybe even a short video clip. The good old adage a picture/video is worth 1000 words. Once the valve operation has been determined good/bad the Avenue to diagnosing becomes that much easier.
Great tip about the customer. I would check to see if the nut came loose on the valve bolt. I have worked a lawnmower that the adjusting nut for the valve was tight, but the main bolt was loose. If not, a compression test than a leak down test.
I think that mouse nest caused overheating, which caused engine issues.
Great video Don, it really shows the reality of the happenings in your business. Looking forward to the fix 👍🏼
Thanks for posting Dony
valve glide got hot and has moved and is holding valve open on the intake side. 😁
My vote would probably be here only because I've ran into this a few times with that very engine. The older craftsman had the kohler pro twins and they never had any issues
When I get something like this (I do farm machinery, tractors and such but it's the same perspective from the customer's point of view) I take a video, show it to the customer, and ask flat out, "... is this what it's doing for you". That verifies two points; One, is this the problem you are paying me to fix? and Two, this is what I found at the very first instant I inspected it. Only issue this might present is that you must make the time to get back to the customer ASAP. But, it's a better situation than, "... it ran better when I gave it to you."
Totally agree with this and the video will have date and time
Briggs Inteks - Twins with slid valve guides, singles with bad camshaft compression releases. Seems like it would run on the other cylinder, though.
I had a similar problem with a Kawasaki engine on a John Deere tractor. Rodents had packed grass clippings and leaves around the head. When the engine was operated the clippings and leaves blocked air flow around the head. The engine got so hot that one of the valve seats popped out. Once repaired the engine ran fine.
I'd check the oil level and condition... the apparent lack of maintenance on the outside may transfer to the inside and could explain a lot.
Really common where I live, people don't take care of anything, even if its theirs....then they expect a repair shop to fix everything for little to nothing, and will cheap ass their way out of the repairs as well, or blame you for the problems they caused themselves from simple lack of routine maintenance.
Early congrats on your 400 K upcoming milestone!
Hi, yes that does happen, and as you say, it makes it hard when it started and ran before.
A good call , contact the customer soon as you know what is wrong with it.
Good video thanks.
I had a Z-turn every time you would move it, it would start. Then you would go to mow with it, and it would quit. This mower drove me batty trying to figure out what was wrong. One day I took the battery out and I just happened to see a loose ground wire and all I had to do was resolder it to the connector. when you would move it, it would ground out to the frame and start, but using the mower the wire would Jiggle around land on a dirty part of the frame, lose ground, and quit. Aggravating, to say the least.
I had one that would not start on a kohler single courage. The valve lash on the intake valve was almost zero meaning less than .001" It would not start and kept backfiring through the carb etc. After adjusting the intake lash to .004", it fired right up. The no-start condition was after doing a full tune up.
Customer relations are very important to keep nice with then. I say that that engine is having valve clearance issues
My guess is the grass prevented proper cooling and it overheated and blew a head gasket. Looking forward to hearing what it is.
I don't have any idea what the problem is. Maybe I missed it when you mentioned it, but what you were bringing it in for?
First thing I would do is check compression, this will tell you a lot.
I have a similar Craftsman that has this popping problem that came up suddenly. I thought it had a bad coil so I replaced both coils but still doing the same thing. Next I was planning on checking the overhead valves and pushrods. My guess is pushrod is bend or popped out of seat or the cam went bad. I'll be watching to see what you find and I hope it's an easy fix! Good Luck Donyboy73!
Stuck value problem with the over heating problem from grass
A lot of times, when people do not service their equipment or do it properly, what happens is the valves lash gets so bad that the push comes off the rocker arm.
Looking forward to the results.. best of luck
Yes the exhaust valve guides have slipped in the heads because of heat build up, bends pushrods bends or holds valves off the seat
Thank you for the video
It has probably been overheated due to lack of air flow and slipped a valve guide. I've had them slide in and out, one time runs like crap, next time may run ok.
Is it a bent pushrod or guide moved from not cooling do to crap in cooling fins... pop valve cover off.
What is that knob selector thing by the operator's left foot position at 1:20 Donny?
I think it overheated every time he used it from all that stuff in the cooling fins for years and driving it up the ramp at a 45 degree angle finally shook a crack in the head enough to separate it.
Why did he want it repaired in the first place?? It must have had an issue. All the best DB
My thoughts as well....and asking the customer doesn't get any truthful answers usually either....they wanted someone to come pick it up so they have someone to blame for the problem they know about but didn't say anything about. This is why I don't work on stuff for people, way too many liars out there looking for their next handout in free repairs.
When you were saying there's grass underneath the lead That was what I was thinking Mice Same thing happened to my tractor Mine was in My shed
I am thinking it is a timing problem. Check Crankshaft/Flywheel key for deformation. Then check Fuel Supply.
I'd say it is the debris on the heads , overheating the cylinders, and this rears the ugly head of a B&S valve guide problem. The valve guides on the exhaust move up blocking the valve from going back down . This usually lets a push rod fall out from under the tappit. Briggs does not sell replacement guides , you have to purchase new head assemblys . That's my guess as to the problem . 😊
It looks like a B&S V-Twin. Notorious for carbon buildup causing the exhaust valve to stick and dislocate the valve guide. Correct fuel mixture along with using Marvel Mystery Oil in the oil and SeaFoam in the gas will keep that from happening. But last one I fixed I had to pull the guide out clean everything and put it back with Loctite cylindrical part bonding compound. I didn’t have any special guide installation tools but if I did I would have still used it.
Needs de- nesting and a good carb and filter clean to start probably. Check the usual repair history boards.
Engine overheated due to insufficient air flow across cylinders, caused by that grass buildup and/or mouse nest. Valve hung up, lash is way off, dropped valve seat, head gasket blew?
Hey dude I bet it has been a while sense you have worked on it, a bought a new carb for my 5Hp Briggs like the one on your old tiller, and it came with fuel filters but I don’t understand where they go as the carb sucks it up so I don’t know where to install them
My guess is fuel. Low on fuel with water on the bottom of the tank. Got mixed on the trailer ride. The tilt on the ramp, gravity fed. Betting all that fuel eventually getting to the carb is largely water.
it can happen that once the engine cools the damage surfaces. The damage could already be done because the temp is the highest after you shut it off because the air vanes on the flywheel have stopped cooling
lack of yearly maintenance
I had a problem that was very similar to this one. Was hard to start for a few weeks, long story short. It was a head gasket.
Camshaft release/ valve adjustment
it got hot no air flow over the heads
Did you try starting fluid?
I don’t know how I’m going to sleep tonight, just waiting until tomorrow! ☮✌🏻
Assuming it has spark, I agree with others that it's a valve problem... either:
1) Overheated and guide slipped
2) Overheated and caused a problem with any plastic parts on camshaft
3) Overheated and valve lash got out of whack
Otherwise, it blew a head gasket. But, i would think it would still try to fire on one cylinder if it had spark? Very interesting!
Valve guide moved, push rod bent because stuck valve or moved guide.
+1, common issue
Head overheated due to nest or debris, causing the exhaust valve guide to move up preventing the valve to fully open and bending a pushrod.
Does this engine have that thing that releases compression, it might have gotten stuck open?
Started snowblower on the truck on a cold day. Put throttle down to idle to warm up. I was about to back it down the ramps.
Before I put it in gear the connecting rod went through the block... Oil just poured out
If my son had done the same I would have said he left the idle too high with no load on the engine.
The problem is clearly labeled on the blower housing “B&S Intek”
Really? I have the 25 hp in my 2006 J.D. 155C which now has about 850 hrs on it. Still has original plugs and has never had any work done to it. Change oil/filter about every 125 hrs, on it's on it's 3-4th air filter and runs great. I'm well aware of the valve guides overheating so make sure there is no mouse nest in it every spring and had the shroud off about 5 times to blow everything clean especially the guides. I haven't even adjusted the valves on it yet and no smoke or oil usage. This sure hasn't been babied here on the farm but I always let it warm up before mowing and let it idle a few minutes before shutting it off. Certainly not one of Briggs best but not junk.
@@jefffrayer8238 correctly maintained you can see a good life, provided you don’t have one with a defective cam. Keeping the fins free of debris has a lot to do with longevity along with proper oil changes.
Float or needle stuck from the drive?
Twins will run on one cylinder so it most likely a two cylinder issue, could be bad diodes ( no fire) or bad cam shaft ( slipped lobes). Not a gravity feed fuel system so I don’t think it would have flooded on the drive to the shop.
Yeah that is a lot of bad luck there for sure. Sounds like the valves like you are saying but hopefully nothing to serious..
In all fairness to both parties, the opposite could also happen where the machine was running fine but the next day it failed for the customer. It was working when it left your shop! The trust needs to go both ways and good customers and shops know this.
Yes that does suck when it happens. Pretty rare event for sure
Valve adjustment.
👍great video
One question, did you see the customer start the machine cold or was it already running. I got a mower and the customer started it and I could restart it but back home I couldn't. After I thought about it they primed it with spray before they started it. So it would not prime or start at my place.
When I arrived he was driving it to my trailer
@@donyboy73 yes so possibly they knew something was wrong and had a way to start it, maybe bypassing something.
It sounds like it is a bent pushrod probably the aluminum rod caused by bad gasoline.
"No, it was running great Don....I just wanted the oil changed and the belts checked"....the usual curse of "the drive off the trailer or through the garage door" and all the demons appear out of nowhere or disappear completely
Valve guide out from overheating.
Loose valve seat?
Keeper for one of the valve springs has fallen off.
My guess is the choke shaft is sticking closed on the Nikkie carburetor. Needs some air to run! 🇺🇸
Push rod full off, maybe poor loose valve adjustment caused it
Stuck or seized up choke/throttle linkage or leaking head gasket.
Valve seat popped out.
The exhaust is plugged.
Could also be water in fuel that gets mixed during transport fuel Will look milky
It probably overheated due to a critter nest and a valve seat popped loose, that would be my guess.
No Idea 🎉
Sheared timing key.
My guess is head gasket(s) due to overheating
Either the customer is not being truthful or it is a very rare case of something giving out at a very inopportune time! Rare like hitting a straight flush in poker!
Your first sentence is the correct answer in many cases....customers are always looking for a way to place the blame onto someone else when they have a problem with their equipment....even on a regular service, never just assume the customer is right about what is wrong, or what needs done....do a full inspection on the equipment even a video/photos of before/after might be quite useful in proof of the state of the equipment when you received it.
My guess is valves are out of adjustment.
I'm thinking a bent push rod.
First effort; auto decomp system which is of course valve related.
The popping kinda sounds like a valve issue but that's a guess. 🤷
Probably the pot holes in the road caused the pushrod to dislodge because of the loose rocker arm tolerance.
Could be!
It overheated from the mouse nest 😊😊😊
Water in the gas??
Internal engine problem
Guessing it's a fuel issue(carburetor).
The least would be a sheared crankshaft key -- that's too easy, though
I think it's a stock value and it all so could be a problem with the cam
Hope it's nothing too serious ... or at least the guy is understanding. The way it's galloping, I'd say a compression issue. Maybe a stuck valve?
The mice ate the wiring. It was firing then during transport the wire shorted out.
My guess is valves out of adjustment
Is that thing Husqvarna built?
What’s troubling is the fact that it’s a twin and it won’t at least run on one cylinder. Usually,even with a rodent infestation making it overheat,the valve guide moving, and bending a pushrod they will still run on one cylinder. I think that the camshaft gear failed.
I'm not sure about a blown head gasket, cause it would need to blow out both, cause it would start with one blown head gasket, it would just sound awful... Popping .... So I'm thinking, no spark cause of bad diode, even no compression, maybe blown head gasket on one side, and out of place valve guide or valve seat.
That little hose from valve cover to fuel pump either broke or pulled out of valve cover
Vibration from transporting can cause issues when there's already a current issue that's not an issue yet.
Flywheel keyway
Well, 1 way it can be avoided is to have a symptom sheet list when picking up any thing.
Have the customer fill out name, address, type of mower, new date, bought new or used, gift, bla, bla, bla, you know what to ask, just building a list by them.
Then list, things like last service date, by who, ethanol gas or treated gas, you know the list to make of thing's to list. Its what you normally find in your area.
What your doing is have a before list by the customer.
Your drawing a line in the sand. Just something that builds a list of to protect yourself.
We know what happened has nothing to do with us, "*:it happens!"
This is a buffer when you call and say, "has the engine been starting okay?"
Customer says, "well sometimes no, sometimes yes."
Well it won't start to get off the trailer, I'll get it inside and let you know in the morning what I find Mr/Ms Mann.
This sheet can be long, longer the better, just make it easy on them by multiple choice answers, have words for answers they can just circle, draw a line thru, check mark, you know how to do this, make it easy for them, if they knew how to fix it, they would have instead calling us.
Take your experience and make your list.
I'll be starting my repair business in the fall/winter/spring by word of mouth. I'll have a list for them to fill out on a clipboard. They are preparing themselves for a diagnosis from doing nothing to the mower for how long and your just correcting their mistakes for lack of maintenance.
Like I said, if they knew what to do, they would have.
Don't expect to get much use out of that list as when something goes wrong with any equipment, the customer is always looking for someone else to blame...list sounds great, but in reality it won't do you any good when the customers are not forthcoming with useful information....
It seems like something in the valvetrain. Maybe out of time, bent valve of valve lash issue, broken cam, broken compression relief? Sorry I know that's a lot. 😂