lawnmower troubleshooting

[MerlinsBeard]

I have a 10 year old John Deere JS36 that's starting to having a symptom where I notice that my lawnmower makes a sound like it wants to quit (but doesn't actually quit... yet).

Feels like the blade clutch is more sensitive then usual this year for some reason. Usually when I make turns with the push mower my grip may not be super tight but I hear no sputtering sound. Now when I make turns I sometimes hear the sputtering sound, but the mower doesn't actually stop. I also notice this sputtering on rough/bumpy terrain.

I do the normal lawnmower maintenance: oil change, spark plugs, air filters, blade sharpening, linkage tightening, but don't have experience with engine troubleshooting. The blade clutch appears fine based on visible inspection.

The blade clutch is attached to springs, to it's possible that there may be some spring fatigue (I just replaced a busted 10 year refrigerator door spring). It's also possible that carburetor needs a service, though I've never done anything like that. There are some youtube videos and it doesn't look too hard.

Just trying to keep the old pushmower going as long as I can. Any other troubleshooting things to look for?

 

[pattenp]

Sounds like carburetor problem.

 

[Jackfre]

New air/oil filter/spark plug and fresh gas. The likely culprit is the gas and the moisture it allows in to screw up the carb. I’d dump the current fuel, add new and run a tank or two through it and see if it cleans itself up some. Otherwise, clean and dip the carb or see what a new carb goes for. If you go new, make sure you get a match.

 

[no704]

I’m assuming this is the kind where you have a bar on the handle that if not held down the engine will shut off. The cable has probably stretched and is on the verge of grounding out the spark. Cable needs to be tightened up.
(Or eliminate it all together, I can’t recommend this, but it’s usually the first thing I do to a push mower. )

 

[MerlinsBeard]

I went through the process of cleaning the carburetor. There was a decent amount of soot looking stuff that came out of the fuel, so I feel that there was some good done there.

I put the mower back together as best as I could tell, but there's a new issue. The mower starts up fine, but the mower sounds like it's really revving high and the vibration is higher than normal, I can feel it in the handle. I'm pretty sure I didn't get something put back right, but I don't know what to look for. Anyone know what's causing this symptom?

 

[The Cobbler]

are you sure you put the linkages back in the proper place?
is any thing binding holding the throttle open? does the throttle move freely when engine is off?
did you move the idle screw on the butterfly?

 

[theoldwizard1]

I have a 10 year old John Deere JS36 that's starting to having a symptom where I notice that my lawnmower makes a sound like it wants to quit (but doesn't actually quit... yet).

Almost dying, but recovering, is a classic sign of dirt in the carburetor, typically the idle/low speed jet. The only way to fix it is remove the carburetor, disassemble and clean all ports/jets. https://www.amazon.com/gp/product/B07F3X6WG8/?tag=atomicindus08-20

 

[MerlinsBeard]

Thanks for the responses. I found that I didn’t connect the governor properly. It was something you have to thread into the carburetor into sideways when it’s not bolted in. When I reattached the carburetor I bolted it to the engine and there’s not enough play to get it threaded. Hopefully the lawnmower is good to go, I’ll report if there’s any other issues.

 

[MerlinsBeard]

Almost dying, but recovering, is a classic sign of dirt in the carburetor, typically the idle/low speed jet. The only way to fix it is remove the carburetor, disassemble and clean all ports/jets. https://www.amazon.com/gp/product/B07F3X6WG8/?tag=atomicindus08-20

Thanks for the link, I definitely need something more professional than a dental tooth pick brush!

 

[theoldwizard1]

Thanks for the link, I definitely need sowgamething more professional than a dental tooth pick brush!

This **IS** what the professionals use ! And an ultrasonic cleaner.

Don't waste your money on a cheap Chinese carb. They seldom work !

 

[MerlinsBeard]

Well, I tested the lawnmower last weekend and it’s not quite there yet. It doesn’t seem to want to stop during mowing, but it’s not without sputtering either. I have a cleaning kit on the way for try two, but I didn’t use carb cleaner the first time and am wanting to know what is a good spray for small engine carb cleaner.

 

[nadogail]

I believe most small engine problems are caused by bad gasoline, I try to run the carburetor dry before I shut the engine down.

Ethanol free gasoline did store well and the fuel systems remained functional; somebody in a pay grade higher than mine decided that ethanol was appropriate to add to our gasoline.

 

[jkuro]

Next time you store it use Sta-bil.

Amazon.com: STA-BIL (22214) Storage Fuel Stabilizer - Guaranteed To Keep Fuel Fresh Fuel Up To Two Years - Effective In All Gasoline Including All Ethanol Blended Fuels - Treats Up To 80 Gallons, 32 fl. oz.: Automotive

Buy STA-BIL (22214) Storage Fuel Stabilizer - Guaranteed To Keep Fuel Fresh Fuel Up To Two Years - Effective In All Gasoline Including All Ethanol Blended Fuels - Treats Up To 80 Gallons, 32 fl. oz.: Fuel Additives - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[MerlinsBeard]

I typically run the mower out the fuel at the end of the season, but I will give this Sta-bil a go.

 

[Imatk]

Have you checked your points?

 

[redmondjp]

Have you checked your points?

On a 10-year-old mower? They haven't used points in mower engines since the 1980s.

 

[Imatk]

Oh ok... I'm old

 

[theoldwizard1]

Well, I tested the lawnmower last weekend and it’s not quite there yet. It doesn’t seem to want to stop during mowing, but it’s not without sputtering either. I have a cleaning kit on the way for try two, but I didn’t use carb cleaner the first time and am wanting to know what is a good spray for small engine carb cleaner.

No spray will clear clogged tiny passages ! Some carb sprays will cause rubber gaskets (like the bowl gasket) to swell and not fit properly.

Few people own or are going to buy an ultrasonic cleaner. I have not tried either but some people have had good results boiling a disassembled carb in water with lemon juice or soaking overnight in water and dollar store degreaser. You still need to probe all passages.

Look for YouTube videos showing cleaning your specific carb.

 

[theoldwizard1]

I believe most small engine problems are caused by bad gasoline, I try to run the carburetor dry before I shut the engine down.

Ethanol free gasoline did store well and the fuel systems remained functional; somebody in a pay grade higher than mine decided that ethanol was appropriate to add to our gasoline.

I agree with your first statement, but disagree with the second !

Running the bowl dry is ALWAYS a good idea. I have used E10 since it first came out. As long as you use the fuel in the tank (don't store it for months on end) it is fine. Old E10 likely has acquired water.

 

[theoldwizard1]

I typically run the mower out the fuel at the end of the season, but I will give this Sta-bil a go.

Dry is better !

 

[no704]

I use TruFuel in my smaller engines, and will always recommend it when chasing a problem like this, and for the last tank run before storage!

 

[MerlinsBeard]

No spray will clear clogged tiny passages ! Some carb sprays will cause rubber gaskets (like the bowl gasket) to swell and not fit properly.

Few people own or are going to buy an ultrasonic cleaner. I have not tried either but some people have had good results boiling a disassembled carb in water with lemon juice or soaking overnight in water and dollar store degreaser. You still need to probe all passages.

Look for YouTube videos showing cleaning your specific carb.

I did finally find a youtube video for my specific carb JS36. I'm pretty sure I missed a tiny passage somewhere. I plan to try to give it another go this weekend if I can find the time, and thanks for the tips.

 

[Uofime]

I did finally find a youtube video for my specific carb JS36. I'm pretty sure I missed a tiny passage somewhere. I plan to try to give it another go this weekend if I can find the time, and thanks for the tips.

A handy tip is to get some stranded wire and remove the insulation then use one or several of the copper strands to clean jets and passages.
Copper is nice and soft so it won’t damage any jets.

I’ve also had good luck soaking carbs in straight pine sol for a couple of days. Won’t hurt any of the plastic or rubber parts you don’t want to take off.

 

[The Cobbler]

I’ve also had good luck soaking carbs in straight pine sol for a couple of days. Won’t hurt any of the plastic or rubber parts you don’t want to take off.

soaked a carb for about 12 or 16 hrs in pinesol original, it turned black. I would have liked to pull it out in 3 or 4 to see what it was like. it did clean it tho

 

[Uofime]

soaked a carb for about 12 or 16 hrs in pinesol original, it turned black. I would have liked to pull it out in 3 or 4 to see what it was like. it did clean it tho

Wonder if it had a magnesium body something else funky/ not aluminum.
What kind was it/ what was the carb off of?

 

[65ranchero]

Next time you store it use Sta-bil.

Amazon.com: STA-BIL (22214) Storage Fuel Stabilizer - Guaranteed To Keep Fuel Fresh Fuel Up To Two Years - Effective In All Gasoline Including All Ethanol Blended Fuels - Treats Up To 80 Gallons, 32 fl. oz.: Automotive

Buy STA-BIL (22214) Storage Fuel Stabilizer - Guaranteed To Keep Fuel Fresh Fuel Up To Two Years - Effective In All Gasoline Including All Ethanol Blended Fuels - Treats Up To 80 Gallons, 32 fl. oz.: Fuel Additives - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

I always use it, along with non ethanol fuel ( if you can get it)
1 oz. per 2.5 gallons of gas dump it in the can then fill it I buy 10 gallons at a time use it all year
They have a Marine Stabil which is supposed to be better but I never tried it.

There is long and hard conversations about which fuel additive/ preservative is best many YouTube vids. also.
The bottom line is use something , it won't hurt it.
Try a small amount of seafoam in the tank, maybe ?

 

[MerlinsBeard]

I have an update. I was able to clean the carburetor with carb cleaner and followed along Steve's small engine channel for the Briggs and Stratton carburetor and everything was performed except for the needle seat replacement. The main jet in the bolt had some build up but gave everything a good spray and poke.

This time I noticed that the engine issues seem to be linked to whenever I engage the pull-assist. It's definitely better than it was as in not dying as fast as it was before cleaning the carburetor, but if I engage the pull-assist, I can eventually get the same symptoms to the point that it started sputtering and choking out. If I use the mower without the pull-assist engaged, I get no symptoms what-so-ever.

I think I've eliminated the carburetor as the source of this rough idling, so looking for ideas of what to try next. Seems like cable replacement may be next but wondering if someone else has had this symptom before. There may be a linkage of some type that connects to the carburetor that may be directly related to the pull assist, still trying to research.

On a different note, is there a recommended time to use a carburetor rebuild kit? If I can find the source of this issue, I may put this on the maintenance agenda at the end of the season. I'm on year 10 right now.

 

[The Cobbler]

Wonder if it had a magnesium body something else funky/ not aluminum.
What kind was it/ what was the carb off of?

Briggs on a John Deere mower . looked to be cast aluminum.

 

[no704]

Had a similar issue, bought a new carb on eBay for $10. Only used the bowl, gasket and main jet. Working great.

 

[mmb617]

Since we're talking about lawn mower troubleshooting I might as well relate my recent experience. I have a good friend who has heard me mention that my 25 year old push mower is nearing end of life. I can always get it started because I know the exact priming procedure it takes, and once started it runs great, but the deck is so rusted I've welded patches on a couple times.

He's in the process of moving some stuff he had in storage and had two push mowers that had problems, so he bought a new one and put the two old ones in his storage unit a couple years ago. He offered to bring them to me and if I could get them running I could have whichever one I wanted.

One of them is a Craftsman self propelled model that wouldn't start, the other was a Bolens that he didn't know if it would start or not but it was retired because his daughter was using it and the blade "fell off".

The Craftsman was real easy. I dropped the float bowl and blew out the main jet, filled it with fresh gas and it fired right up and ran well.

Preliminary examination of the Bolens with the blade fell off problem showed that the blade fell off because the retaining bolt was sheared off and also the cast iron collar that keys the blade to the crankshaft was broken. I couldn't see an obvious bend in the crankshaft but I didn't have a good feeling about this one.

I tried to pull the starter rope and couldn't budge it, so I pulled the plug so I wasn't fighting compression. When I pulled the plug I found the cylinder was full of oil, which was why I couldn't pull the rope. At that point I figured the engine was toast, but I wanted to be sure, so I got the oil out of the cylinder and tried the pull rope again. The engine will rotate just so far then it's super tight. I figure something is bent internally, probably the crankshaft or connecting rod. I have to assume the daughter hit something that stopped the blade instantly and caused the damage.

 

[captaindiode]

My brother's push mower would not run right. Turned out that stinkbugs had overwintered in the muffler and clogged it up.

 

[tdkkart]

This will likely eliminate a lot of dickin' around....

https://www.amazon.com/dp/B07MVWP8ZS/?tag=atomicindus08-20

BTW, I never run carbs dry for winter storage, mainly because you rarely get them completely dry, and end up with a small puddle of fuel left over, which then evaporates leaving a mess of scale and debris in the bottom of the bowl, which in the spring gets sucked up into the works. I leave the wet with plenty of fuel in the tank, and rarely have issues.

 

[laser3kw]

BTW, I never run carbs dry for winter storage, mainly because you rarely get them completely dry,

I leave a small amount in the tank and put a piece of plastic bag under the gas cap. The next season, I dump it out then put fresh gas in and start it. Don't run with old gas, I does weird things.

 

[MerlinsBeard]

Still musing on the issue. I had a thought that when I engage the pull assist on the John Deere JS36, there is a safety bar I have to hold down, and I have to bend the top of the handle and push forward.

I know that letting go of the safety bar still stops the mower immediately, but I'm wondering if there is some connection between engaging the push mower pull assist and the safety bar cable choking out the carb.

Maybe there is some tension fatigue and somehow the safety bar is inadvertently barely starting to choke out the carb when I bend the top of the lawnmower handle forward. Does this sound plausible to anyone?

 

[PoorUB]

John Deere JS36

The safety handle controls a engine brake and kill switch. No control to the carburetor.

 

[theoldwizard1]

I think I've eliminated the carburetor as the source of this rough idling, so looking for ideas of what to try next.

99% of ALL small engine performance problems are carburetor or air/fuel problems. (Vacuum leaks can cause a lean condition.) Electronic ignition (actually built into the coil) has been "standard" since the 80s (?). Check the gap on the coil to flywheel (use a business card as a guage).

DO NOT WASTE YOUR MONEY ON A CLONE CARBURETOR!

 

[theoldwizard1]

I leave a small amount in the tank and put a piece of plastic bag under the gas cap. The next season, I dump it out then put fresh gas in and start it. Don't run with old gas, I does weird things.

A pro said that every piece of equipment that comes in the shop get fresh fuel. If possible, the old fuel is saved to inspect for debris and water.

 

[MerlinsBeard]

99% of ALL small engine performance problems are carburetor or air/fuel problems. (Vacuum leaks can cause a lean condition.) Electronic ignition (actually built into the coil) has been "standard" since the 80s (?). Check the gap on the coil to flywheel (use a business card as a guage).

DO NOT WASTE YOUR MONEY ON A CLONE CARBURETOR!

I think my main issue is I don't have the intuition to really zone in on the problem, especially when the behavior is so intermittent, so maybe the best alternative is to just try to piece together a list of issues that can cause this and try to eliminate each one by one, maybe from cheapest to most expensive, within limits. Thanks for the continued suggestions, I'll see if I can craft a list of things to try.

Do you recommend a carburetor rebuild kit to try for the briggs and stratton? Am I better off trying to replace everything that I can that comes in these "tune up" kits? I guess I'm still partial to try to keep the JS36 even though it's been out of production for a decade.

 

[MerlinsBeard]

I had another thought. What causes the engine to stall when you don't scrape your deck or you mow in wet grass? Is it possible that the drive assist system is causing a similar scenario intermittently. I know I haven't maintained the drive assist system at all.

I plan to try to mow without the drive assist this weekend (takes about 75 minutes to mow the yard) and see if I have any intermittent symptoms. Intermittent symptoms show up several times during the mow when I use the drive assist mechanism. If I don't have any symptoms not using the drive assist, it feels like the drive assist must be involved somehow.

 

[Firebrick43]

I had another thought. What causes the engine to stall when you don't scrape your deck or you mow in wet grass? Is it possible that the drive assist system is causing a similar scenario intermittently. I know I haven't maintained the drive assist system at all.

I plan to try to mow without the drive assist this weekend (takes about 75 minutes to mow the yard) and see if I have any intermittent symptoms. Intermittent symptoms show up several times during the mow when I use the drive assist mechanism. If I don't have any symptoms not using the drive assist, it feels like the drive assist must be involved somehow.

In those cases its that the mower's engine is physically overloaded beyond its torque rating and it pulls it down. This is unlikely to happen intermittently?