Vapor lock.
That's what it sounds like to me.
Sent from my SM-S205DL using Tapatalk
That's what it sounds like to me.
Sent from my SM-S205DL using Tapatalk
7hp Briggs runs for 30min then dies
I have a vintage International Cadet 75 rear engine riding mower with an original Briggs and Stratton vertical shaft 7hp engine. Its my main workhorse mower and been using it solidly for about 3 years now.
I have been trying to track down a weird problem where it will start running rough and die after 20-30minutes of solid mowing.
Wont restart unless choke is fully open and immediately dies if throttle is lowered below full choke. If I wait 5 minutes it will start and run again like normal without choke. I get maybe another five minutes of mowing, and it will die again.
I noticed it seems to be related to heat. If I run the mower extra hard, it will do this more often and quicker. Sometimes if I leave the throttle lower and mow in a lower gear putting less load on it, it will be OK.
Blew out the cover with air compressor. Still happened.
Replaced ignition and spark plug. Still happened.
Changed gas cap, also tried leaving it cracked oepn. Changed oil, seemed to go longer but still happened.
Suspected starter clutch hanging and disconnected the top from it. No change.
Adjusted carb to be less lean, seems to happen earlier.
I noticed randomly that really bumpy ground will make it sometimes missfire a bit and can sometimes start it on the path to dying like this.
Got a spark tester and left it on the mower. Spark is identical before and after. I see sparks when its cranking right after dying and wont start.
I am thinking next maybe to check compression when running and immediately after it dies to see if a valve is sticking or something?
Any ideas….
Briggs 170707
Type: 1198-01
Code: 73041311
I have been trying to track down a weird problem where it will start running rough and die after 20-30minutes of solid mowing.
Wont restart unless choke is fully open and immediately dies if throttle is lowered below full choke. If I wait 5 minutes it will start and run again like normal without choke. I get maybe another five minutes of mowing, and it will die again.
I noticed it seems to be related to heat. If I run the mower extra hard, it will do this more often and quicker. Sometimes if I leave the throttle lower and mow in a lower gear putting less load on it, it will be OK.
Blew out the cover with air compressor. Still happened.
Replaced ignition and spark plug. Still happened.
Changed gas cap, also tried leaving it cracked oepn. Changed oil, seemed to go longer but still happened.
Suspected starter clutch hanging and disconnected the top from it. No change.
Adjusted carb to be less lean, seems to happen earlier.
I noticed randomly that really bumpy ground will make it sometimes missfire a bit and can sometimes start it on the path to dying like this.
Got a spark tester and left it on the mower. Spark is identical before and after. I see sparks when its cranking right after dying and wont start.
I am thinking next maybe to check compression when running and immediately after it dies to see if a valve is sticking or something?
Any ideas….
Briggs 170707
Type: 1198-01
Code: 73041311
1 - 19 of 19 Posts
Isnt that ruled out by the gas cap being removed and having no effect? I suspected that first and have multiple of these mowers so I swapped fuel caps with no change…
I'm thinking you have a small obstruction that is causing a low flow of fuel. I would take the carb apart clean it up.
I can get a whole new carb for 24 shipped, I will likely do so just to remove that out of the equation. Carb on it is original and likely older than I am.
Yes, does sound like a carb issue. Could be a plugged fuel line or filter.I can get a whole new carb for 24 shipped, I will likely do so just to remove that out of the equation. Carb on it is original and likely older than I am.
I have seen a similar problem caused by a loose valve seat in the block. ....When the heat builds up, the aluminum block expands slightly and the steel valve seat lifts up losing compression. .....When the engine sits for a short time, the aluminum contracts and the seat is tight until it heats up again and the cycle is repeated.
If that is what is happening, the valve seat can be staked in place using a center punch. ....I also use a flat punch to peen the aluminum over to retain the valve seat.
If that is what is happening, the valve seat can be staked in place using a center punch. ....I also use a flat punch to peen the aluminum over to retain the valve seat.
Bumpy ground missfire is Carb related. Most likely your float level is set to shut the fuel off a bit to early. If you have the carb off and turn it upside down the Float should be angled down torwards the carb a tiny bit. Having it even with the carb body or slightly up-swep will make it lean out and sputter every time you hit a bump.
Do you have the original muffler on it that sticks out past the engine a couple inches? If not then you could be blowing hot exhaust rite at the carb if you don't have some sort of deflector on the muffler.
The muffler was rotted off on my old 85 Special and it would cause it to boil the fuel in the float bowl after about 10-15 minutes.
The exhaust port should be threaded for 3/4" pipe thread if it's similar to my 85. I put a 90* elbow and a hot dog muffler on mine. They sound ok and getting the muffler away from the carb and sealing up the massive exhaust leak that it had, fixed the problem.
This is like the larger 4-8hp hot dog muffler that I used. They are a bit poppy? and loud under load but it worked good and didn't cost much money. They were around $4 at our local hardware store back when I got mine 20+ years ago. https://www.amazon.com/Silencer-Muffler-thread-Stratton-No-294599/dp/B07B2M4SBS
You could put one of these on your muffler. https://www.amazon.com/Briggs-Stratton-795036-Side-Out-Deflector/dp/B0038U3KZ6
Do you have the original muffler on it that sticks out past the engine a couple inches? If not then you could be blowing hot exhaust rite at the carb if you don't have some sort of deflector on the muffler.
The muffler was rotted off on my old 85 Special and it would cause it to boil the fuel in the float bowl after about 10-15 minutes.
The exhaust port should be threaded for 3/4" pipe thread if it's similar to my 85. I put a 90* elbow and a hot dog muffler on mine. They sound ok and getting the muffler away from the carb and sealing up the massive exhaust leak that it had, fixed the problem.
This is like the larger 4-8hp hot dog muffler that I used. They are a bit poppy? and loud under load but it worked good and didn't cost much money. They were around $4 at our local hardware store back when I got mine 20+ years ago. https://www.amazon.com/Silencer-Muffler-thread-Stratton-No-294599/dp/B07B2M4SBS
You could put one of these on your muffler. https://www.amazon.com/Briggs-Stratton-795036-Side-Out-Deflector/dp/B0038U3KZ6
You changed quite a few items, it definitely sounds fuel related, what about the fuel filter? when they are clogging it will let gas go through for a while and then plug up, when the flow stops the sediment falls to the bottom and you are then able to restart and run until it does it again. If you have one take it off and tap the inlet side on a table and see what comes out.I have a vintage International Cadet 75 rear engine riding mower with an original Briggs and Stratton vertical shaft 7hp engine. Its my main workhorse mower and been using it solidly for about 3 years now.
I have been trying to track down a weird problem where it will start running rough and die after 20-30minutes of solid mowing.
Wont restart unless choke is fully open and immediately dies if throttle is lowered below full choke. If I wait 5 minutes it will start and run again like normal without choke. I get maybe another five minutes of mowing, and it will die again.
I noticed it seems to be related to heat. If I run the mower extra hard, it will do this more often and quicker. Sometimes if I leave the throttle lower and mow in a lower gear putting less load on it, it will be OK.
Blew out the cover with air compressor. Still happened.
Replaced ignition and spark plug. Still happened.
Changed gas cap, also tried leaving it cracked oepn. Changed oil, seemed to go longer but still happened.
Suspected starter clutch hanging and disconnected the top from it. No change.
Adjusted carb to be less lean, seems to happen earlier.
I noticed randomly that really bumpy ground will make it sometimes missfire a bit and can sometimes start it on the path to dying like this.
Got a spark tester and left it on the mower. Spark is identical before and after. I see sparks when its cranking right after dying and wont start.
I am thinking next maybe to check compression when running and immediately after it dies to see if a valve is sticking or something?
Any ideas….
Briggs 170707
Type: 1198-01
Code: 73041311
I agree with Kip, fuel filter, fuel line, vent in fuel cap, vaporlock, does this engine have a pulse fuel pump? If it does then dismantle and clean/rebuild it. You can try putting tin foil around fuel line to keep engine and exhaust heat from boiling the fuel.
Keep us posted!
Keep us posted!
I have a vintage International Cadet 75 rear engine riding mower with an original Briggs and Stratton vertical shaft 7hp engine. Its my main workhorse mower and been using it solidly for about 3 years now.
I have been trying to track down a weird problem where it will start running rough and die after 20-30minutes of solid mowing.
Wont restart unless choke is fully open and immediately dies if throttle is lowered below full choke. If I wait 5 minutes it will start and run again like normal without choke. I get maybe another five minutes of mowing, and it will die again.
I noticed it seems to be related to heat. If I run the mower extra hard, it will do this more often and quicker. Sometimes if I leave the throttle lower and mow in a lower gear putting less load on it, it will be OK.
Blew out the cover with air compressor. Still happened.
Replaced ignition and spark plug. Still happened.
Changed gas cap, also tried leaving it cracked oepn. Changed oil, seemed to go longer but still happened.
Suspected starter clutch hanging and disconnected the top from it. No change.
Adjusted carb to be less lean, seems to happen earlier.
I noticed randomly that really bumpy ground will make it sometimes missfire a bit and can sometimes start it on the path to dying like this.
Got a spark tester and left it on the mower. Spark is identical before and after. I see sparks when its cranking right after dying and wont start.
I am thinking next maybe to check compression when running and immediately after it dies to see if a valve is sticking or something?
Any ideas….
Definitely check compression hot.
I found most of those old small engines would not run if compression less than 60 psi
Briggs 170707
Type: 1198-01
Code: 73041311
Ok updates. Got a brand new carb. Was totally expecting jank for 24 dollars but its actually very very nice.
Put it on and was surprised it started first start like stock. Thought I was going to have to tune it to get going but no it was spot on from the box.
I ran the mower hard trying to see if this was it. About 4 passes of my yard and boom started to hear the signature puttering start but oddly the mower worked through it without stopping.
When it did start sputtering a bit I reached down and tugged on the choke cable directly and it revived it and went back to normal when I let go. That was kinda weird. I was able to finish the yard without it dying but I am still wondering if something wrong with the throttle/governor system maybe?
I see its a bit gunky behind the cover. Maybe something there is getting out of whack when hot?
Bumps seem to still have something to do with it but its also the hill so maybe when I go down hills the governor letting go of the throttle to coast is getting somehow effected such that it isnt calling for enough throttle when it bogs?
Any ideas? Should I replace springs?
Put it on and was surprised it started first start like stock. Thought I was going to have to tune it to get going but no it was spot on from the box.
I ran the mower hard trying to see if this was it. About 4 passes of my yard and boom started to hear the signature puttering start but oddly the mower worked through it without stopping.
When it did start sputtering a bit I reached down and tugged on the choke cable directly and it revived it and went back to normal when I let go. That was kinda weird. I was able to finish the yard without it dying but I am still wondering if something wrong with the throttle/governor system maybe?
I see its a bit gunky behind the cover. Maybe something there is getting out of whack when hot?
Bumps seem to still have something to do with it but its also the hill so maybe when I go down hills the governor letting go of the throttle to coast is getting somehow effected such that it isnt calling for enough throttle when it bogs?
Any ideas? Should I replace springs?
To me it looks too close carburetor to exhaust which would heat carb and fuel line.
I would fabricate something out of metal, aluminum probably. I'd use cardboard first as a template then cut aluminum, something like this to attach under a headbolt or elsewhere.
You want to keep heat away from fuel, so a plate between the two .
![]()
![]()
Sent from my SM-S205DL using Tapatalk
I would fabricate something out of metal, aluminum probably. I'd use cardboard first as a template then cut aluminum, something like this to attach under a headbolt or elsewhere.
You want to keep heat away from fuel, so a plate between the two .
Sent from my SM-S205DL using Tapatalk
First. That looks to be the original fuel line with the paint still on it. I would replace the fuel line first. The inside of the line could be disintegrating or plugged with anything restricting flow and causing the engine to run hot and thus causing vapor lock in the fuel line.
Second. The fuel line is very close to the exhaut. Try using foil around the hose to dissipate the heat. Try it and see what happens. Wouldn't take but a second.
Second. The fuel line is very close to the exhaut. Try using foil around the hose to dissipate the heat. Try it and see what happens. Wouldn't take but a second.
I thought about making a plate to shield it but its really not that close the photo angle just came out that way. Its nearly 6 inches above it.
I have a few other of these and already changed fuel lines. Its just tractor supply International Harvester White. Other mower it came off of was repainted by the guy before I got it.
I suspect the governor honestly. Seems if something makes it bog and drop rpm the throttle doesnt try to raise up as high as it was.
But yes I have tried everything so I will put some foil around it for the next try.
I have a few other of these and already changed fuel lines. Its just tractor supply International Harvester White. Other mower it came off of was repainted by the guy before I got it.
I suspect the governor honestly. Seems if something makes it bog and drop rpm the throttle doesnt try to raise up as high as it was.
But yes I have tried everything so I will put some foil around it for the next try.
I would be a bit suspicious of that fuel valve/nipple on the carb. I would unscrew it from the carb and see how much gas flows through it to get a better idea of how much is getting to the carb.I thought about making a plate to shield it but its really not that close the photo angle just came out that way. Its nearly 6 inches above it.
I have a few other of these and already changed fuel lines. Its just tractor supply International Harvester White. Other mower it came off of was repainted by the guy before I got it.
I suspect the governor honestly. Seems if something makes it bog and drop rpm the throttle doesnt try to raise up as high as it was.
But yes I have tried everything so I will put some foil around it for the next try.
I doubt the fuel line is too close. I have to 11HP Briggs engines and they both have the line like that. Though it sure is not 6 inches above...
1 - 19 of 19 Posts
Garden Tractor Forums
A forum community dedicated to garden tractor owners and enthusiasts. Come join the discussion about performance, modifications, attachments, classifieds, troubleshooting, maintenance, and more!
Full Forum Listing
Top Contributors this Month
View All
Mark 149 J.
68 Replies
29 Chev
49 Replies
knucklebuster283
47 Replies
