[Runvsofthisbull]

Hello I'm new to the site and to mowers. I picked up a John Deere JS36 mower off craigslist and it's been running great for about a year until yesterday. I took the front wheel off for a minor repair, then realized the air filter needed cleaning so went to the store and bout a tune up kit with filter, oil, and spark plug. I had recently changed the oil so I was holding off on that but swapped the filter and the plug and started it up. A little black smoke came out, but stopped after a few seconds. In cut a few rows of grass but it didn't seem like it was running right. I investigated the filter and found it wet with fuel? Not sure why/how this happened, but cleaned that area and proceeded to cut two more rows, but still seemed like it was running rough so I shut it down. I opened the dip stick and it was smoking a little in there (which may be normal since it was hot), but I then decided to let it cool and change the oil since it did seem low now at this time. I then proceeded to crank the motor and nothing. I can't even pull it one inch. I was afraid I seized up the motor so basically took it apart with hand tools, except for the flywheel since I don't have a puller (yet). I did, however still see a flywheel key after i took off the 15/16 inch flywheel bolt, but not sure about the bottom half (i did not sheer anything). But got the valve cover off and see the piston and valves and i can turn them by turning the flywheel so my questions are now what? The piston and valves look ok from the outside except one minor nick in the piston. I'll post pics later, but any ideas of what is going on? I'm lost but would rather learn how to rebuild this motor if I have to rather than bite the bullet and buy a new $400 mower. Please help and thank you.

 

[Austen]

Welcome!

It sounds like it was running rich due to a sticky float perhaps. My guess is that when the mower was sitting, fuel was leaking into the cylinder to the point where when you tried to start it, it locked up due to too much fuel being in the cylinder. Pulling the sparkplug and then attempting to turn it over should have cleared it out assuming that's the problem. I would install a carb rebuilt kit and or take a good look at the float operation.

 

[Runvsofthisbull]

So i took the mower apart and cleaned and put back together and now it starts but it seems like its just running rough still so yes I will take your advice and get a carb rebuild kit if necessary, but I think today I'll check the compression since I can actually pull the cord now. I'll be back with an update. I think the problem was the air intake tube fell off so there was a lack of air/too much fuel. That's fixed now though so I'll see.

 

[Runvsofthisbull]

Ok did a compression test and it only came back at about 58-60 ish. What now? New rings and piston and rebuild + a sand paper hone? Or just chuck it and buy another? I'm not sure what to do now? Any input appreciated.

 

[Mark / Ohio]

With the compression release that might not be that bad of compression. Maybe you are already aware of it but see:

Compression Reading | Frequently Asked Questions | Customer Support | Briggs & Stratton

I would tend more with Austen toward a carb problem. But I am wondering about the nick in the piston and how that got there. Maybe it had the wrong spark plug at some point and the piston hit the end of the plug?

 

[Runvsofthisbull]

Hmm yea that is exactly what the nick seems to look like now that you mention it. Do you guys typically just hand tighten your plugs? I have it gapped at 0.03 inches which is what is recommended but it's difficult to torque it to the 15ft/lbs with my torque wrench.

 

[Mark / Ohio]

I've always screwed them in finger tight and then just lightly snug them with a wrench maybe an additional 1/8 turn. My neighbor years ago used to only finger tighten them. One day POP! out it came while he was mowing and took part of the threads along with it.