John Deere JS38 push mower

[dannac]

Have a John Deere JS38 push mower.
Purchased in 2012 and has worked great.

Sometimes bag grass, and stop engine to empty clippings.
Never had problems with it re-starting until end of last season.

When I stop it to empty clippings, it will not start unless I leave it sit for approx 15 minutes ... as if it's flooded.

Oil was changed every year, and occasional changing of spark plug with most recent last year.

Appreciate some advice or something to check.

 

[mechanic mark]

https://images.homedepot-static.com/catalog/pdfImages/08/086d911d-27cb-4dc2-b5b4-52c3fb95469f.pdf

Adjust intake & exhaust valves with engine cold.

Briggs and Stratton Valve Clearances

outdoorpowerinfo.com

Scroll down above page for your engine valve clearance specs. B&S Engine Model # should be on sticker, specs. plate, or stamped on blower housing.
Watch video below & see if you're up to adjusting valves.

HOW TO ADJUST VALVES ON B&S JD JS38 ENGINE - Google Search

 

[dannac]

https://images.homedepot-static.com/catalog/pdfImages/08/086d911d-27cb-4dc2-b5b4-52c3fb95469f.pdf

Adjust intake & exhaust valves with engine cold.

Briggs and Stratton Valve Clearances

outdoorpowerinfo.com

Scroll down above page for your engine valve clearance specs. B&S Engine Model # should be on sticker, specs. plate, or stamped on blower housing.

Thanks for the reply ... but that is probably over my head.

I've never taken an engine apart which I'm assuming I'd have to do to get to the valves.
... and if I got there I wouldn't know the intake valve from the exhaust valve or how to adjust.

Thanks

 

[dannac]

Engine info it that may help

 

[mechanic mark]

Results

www.briggsandstratton.com

Engine Specs. see Operators Manual page 10 above.
Intake .005- .007, i would set at .006, Exhaust .007-.009 i would set at .008.
or you can do as you choose dannac: Intake .005 Exhaust .007 or Intake .007-Exhaust .009
Take your time & let us know how it goes, thanks dannac, Mark

 

[dannac]

Thanks Mark ... looked at the video, pretty sure I can handle that.

What I'm not sure of is the clearance values to use.

 

[Freddie21]

I usually go midway between specs. .006 and .008

 

[grumpyunk]

You have what is known as a 'flat head' engine per the diagram at partstree.com. As the valves wear, the tip of the valve will get closer to the tappet which opens the valve when the cam lobe pushes on it. There must be clearance between tappet and the valve stem or the valve will not close which causes loss of compression.
The symptom is that it happens when the engine is hot. The valve expands in length as it heats up, reducing the clearance until the valve barely seats on the top of the engine(valve seat). That makes it hard to start when it gets hot.
You can usually remove the head and then the tappet cover and finally the keeper and spring from the valve stem. You can then push the valve out of its guide. Use a grinder or file to remove a few thousandths off the tip of the valve stem. Best to keep the tip square so it meets the tappet nicely. Put the valve back in place and use a 'feeler gauge' to measure the gap between valve stem tip and tappet.
You can likely improve the way the engine runs by lapping the valves. Search for the process, but essentially it is using a paste that has abrasive between valve and seat to make the meeting surfaces meet better and thus seal better. Not difficult, and generally after that many years, the seats are tired and need a freshening. You will more than likely regain a lot of lost power and the engine will also likely use less fuel.
Kind of a fun project to learn about small engines at a low cost.
tom

 

[dannac]

Thanks for the reply Freddie21.

Thanks for that info tomw0 ... your explanation makes sense to me.

I took cover off and not sure if I want to try this with the cutting season starting.
May have to wait, as this would take me quite awhile not being familiar with this.

Did notice a little liquid at bottom of air filter frame, gas I think.

 

[Zue]

Have a John Deere JS38 push mower.
Purchased in 2012 and has worked great.

Sometimes bag grass, and stop engine to empty clippings.
Never had problems with it re-starting until end of last season.

When I stop it to empty clippings, it will not start unless I leave it sit for approx 15 minutes ... as if it's flooded.

Oil was changed every year, and occasional changing of spark plug with most recent last year.

Appreciate some advice or something to check.

Sometimes the electric coil for the spark plug can heat up and stop working. Check the spark from your coil going to the spark plug and make sure that is still working when you try to restart your motor. Coils tend to fail when they get hot not when they’re cold.