Flying Site/field Maintenance
- Thread starter LitterBug
- Start date
Fun times at the field. Finally time to mow and the mower died after barely getting started. Backfiring through the intake is a big sign that the exhaust valve is not opening. Pulled the valve cover off and found the exhaust rocker stud was loose. Looked at the valve stems and saw that the exhaust valve guide had walked out preventing it from opening. Fortunately the rocker stud backed out rather than bending the pushrod, rocker and other parts. Going to pull the head and look into getting the guide fixed/replaced.
Exhaust valve seal is missing, but based on the factory engine manual, it may not have had one to begin with. Will pull the head and hopefully get it fixed so we can have a nicely manicured landing strip.
LB
Exhaust valve seal is missing, but based on the factory engine manual, it may not have had one to begin with. Will pull the head and hopefully get it fixed so we can have a nicely manicured landing strip.
LB
MrClean
Well-known member
I was mowing the CL circle and the walk paths at my field last week and the mower started cutting out. I managed to get it back to and up on the trailer by pulling out the choke. Got it home and it ran off the trailer and around the garden fine. Later my grandkids used it to drive around the yard with the trailer full of kids on and the problems came back. Check air filter, cleaned the carb and govenor mechs checked to see if there was any mouse nests under the fan. Finally decided it was Fuel filter, fuel pump or needing a carb overhaul. Luckily, the cheapest and easiest Fuel Filter swap fixed it. That sucker gets changed out every 100 hours, which is constantly. But I guess it was plugged. Got 5 hours of operation on the new filter now and it wasn't going 30 minutes. Must have sucked a booger out of the tank though the fuel wasn't a month old. The Main strip is mowed by a service but the city doesn't mow down the surrounding fields anymore but a couple times a year. So we mow paths out to the Fence on the property line and I put in a couple more crossovers last year because it the pasture grass was getting close to 5 foot tall in places. Kinda a tough slog to get out through. Should have taken a plane to the field today, it was 10 mph winds but constant BUT I started the day off babysitting early and didn't think the throw it in.
I'm going out on a hunch here and guessing the BAD valve is the one with all the black gooey oil around it? Wish it was as simple of a fix as mine but at least it's not too bad. Grass isn't going to get any shorter for a good 5 months.
I'm going out on a hunch here and guessing the BAD valve is the one with all the black gooey oil around it? Wish it was as simple of a fix as mine but at least it's not too bad. Grass isn't going to get any shorter for a good 5 months.
Yeah, the exhaust valves being hotter tend to cook the oil and cause it to stick around them. Especially if the engine runs hot. If it runs past the oil seal and builds up on the exhaust port side of the valve, it will push the valve guide toward the valve spring till the spring/valve can no longer move enough to open the valve. In the second picture with a close up of the springs, the valve guide on the left spring can be seen very close to the top of the spring and missing the seal. It will require removal of the head. Hopefully the guide hole is not worn so a new guide can be pressed in if the old guide is out of spec. Otherwise, it's pick up a used head. A new bare head is $200+. A complete used head with all rockers, springs, valves, and gasket sets is between $50-$80. We'll see how bad it is after the head is off.
hankflies03
Active member
automatic lawn mower!
Yes, but it leaves odd shaped lumps....
Took my used 20 YO mower to the field and mowed "everything". Waiting for gasket set to arrive. Going to pull the head off the field mower tomorrow after work.
Found a good "ditch" which allows me to drive mowers straight off/on truck. In the past, it has required lifting mowers over the edge of the truck bed to clear the mower deck.
Found a good "ditch" which allows me to drive mowers straight off/on truck. In the past, it has required lifting mowers over the edge of the truck bed to clear the mower deck.
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And fertilizes at the same time.
Pulled the head today... Taking it over to my buddy's shop tomorrow to see what we can do with the guide. I don't have a valve spring compressor to pull it apart any further. The springs are just firm enough I can't do it without.
Ordered a gasket set which should be here in the next day or so. Need to track down a set of new valve seals too.
This is far too easy to work on compared to a car with all the extra gizmos everywhere. LOL
Ordered a gasket set which should be here in the next day or so. Need to track down a set of new valve seals too.
This is far too easy to work on compared to a car with all the extra gizmos everywhere. LOL
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Got the exhaust valve all pulled apart. Guide is supposed to be 6.2mm below the valve cover lip. It was 4.8 Above....
Pushed it back in, but the further in it goes, the looser the fit all the way till it is no longer a friction fit. Going to use Pematex 64000 to hold it in place. It's a high temp glue similar to Loctite 620 for holding loose to press fit cylindrical objects in place. ( Ie bearings, bushings, sleeves, valve guides, etc).
Looks as if this has been a slow progression rather than a single overheating that caused it. Valve, guide, Guide to valve, and valve to valve seat are in excellent condition, so it would be a waste to dump this head. There isn't supposed to be a valve seal on the exhaust valve for this engine. The engine manufacturer shop manual lies. LOL
Pushed it back in, but the further in it goes, the looser the fit all the way till it is no longer a friction fit. Going to use Pematex 64000 to hold it in place. It's a high temp glue similar to Loctite 620 for holding loose to press fit cylindrical objects in place. ( Ie bearings, bushings, sleeves, valve guides, etc).
Looks as if this has been a slow progression rather than a single overheating that caused it. Valve, guide, Guide to valve, and valve to valve seat are in excellent condition, so it would be a waste to dump this head. There isn't supposed to be a valve seal on the exhaust valve for this engine. The engine manufacturer shop manual lies. LOL
I have NEVER used gas additives. I have not had any issues that require them.
Why would we need them?
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Foamforce
Elite member
I use the recommended amount of Stabil in my snowblower because it doesn’t get used for most of the year and it doesn’t have a gas drain tube. I also use only non-ethanol gas. I haven’t had any problems with gunked up carbs since I started doing both of those things. Cleaning carbs is easy enough, but somehow I manage to get a mist of carb cleaner in my eye about half the time I do it. 😭
I've been using small motors for over 4.5 decades and never had any fuel/carb issues and take no precautions avoiding ethanol or using stabilizers. I never drain the tanks either. Maybe the fuel supply in central ohio is better than most?
My generator has gas in the tank of unknown age. Still fired up earlier this year and ran perfectly fine. Only thing I do is shut off the fuel valve and let the carb Run dry before putting it away.
My generator has gas in the tank of unknown age. Still fired up earlier this year and ran perfectly fine. Only thing I do is shut off the fuel valve and let the carb Run dry before putting it away.
I don’t use any additives, I use gas with ethanol. The ethanol will clean all of the varnish from your system far better than any addictive.
At the end of the respective season, I siphon all the gas from both my lawn mower and snow blower. I will then run the engine until all of the remaining gas is gone.
Make sure your motor can use ethanol. Anything build this century should be OK. The carburetor seals is some older motors were made too cheaply to use with ethanol.
At the end of the respective season, I siphon all the gas from both my lawn mower and snow blower. I will then run the engine until all of the remaining gas is gone.
Make sure your motor can use ethanol. Anything build this century should be OK. The carburetor seals is some older motors were made too cheaply to use with ethanol.
danskis
Master member
Its hard to get to the truth these days - especially on the internet - but I'm with you @Foamforce. If you're engine sits for a while I think the best thing you can do is use non-ethanol gas and a stabilizer. I do this in my old 4 stroke pull start mower. Before I started doing this it was always a problem starting it up in the Spring. (I replace the plug and filter every spring) In a car I like to run an injector cleaner when I go on long trips of over 1,000 miles 2-4 times a year. This usually gets 3-5 tank fulls of treated gas going through on road trips. Of course you can buy treated gas but its usually more expensive.
