John Deere puttered out while mowing, engine stopped, white smoke came from engine

rpm5101 · Jul 1, 2019

Last year I bought a John Deere D120 from a neighbor; it had 80 hours on it and ran great. Towards the end of the mowing season, I started having issues getting it started. The engine would crank, but the flywheel wouldn't turn over. It all started when I got stuck going around a tree over some wet grass. I was going over a big root (I didn't hit the root with the blades), wheels started spinning, so I had to turn the mower off and lift it over the root. When I turned it off, the engine backfired and made a very loud popping noise. From then on, I could only get it to start if I manually turned the flywheel over past what felt like a lot of engine compression (video later will show this).

I brought it to a small engine shop and they said it could be a worn down crankshaft or possibly a spring broke in the crankshaft and that the engine wasn't releasing compression. I didn't have the $500 they wanted to fix it, so I figured I'd just deal with having to turn the flywheel over every time I wanted to start the mower.

This year everything has been going fine, other than the starting issues, and I've put another 20 hours on the mower (I mow 3 other lawns in my neighborhood to help out elderly). But yesterday, I did one lawn and towards the end of it, I noticed my engine start to putter every once in a while. It would putter a bit, lose power and slow down, then kick right back up. I came back home and had to do my lawn, and it started puttering more and more. After about half an hour, it was puttering like crazy and I could tell it was about to die, so I took this video Mower - YouTube. A little bit of white smoke started coming out of the front of the engine and it smelled like burnt gas.

Now it won't start at all. After turning the flywheel past the compression, it spins and spins and spins but never starts. When I move the throttle level from choke to throttle, the engine just pops and cuts out. Video Turning on - YouTube Can't start with the throttle on either.

Any advice or help would be greatly appreciated because these lawns are getting long after a week of rain and I need to get them done. I'm thinking it might be a bad fuel filter, fuel pump, or carburetor, but I think that's unrelated to the starting issues too.

TimberHole · Jul 1, 2019

Is the clutch disengaging???? When you turn the crank by hand are the blades trying to turn?? Is there any type of brakes used on any of the pulleys to stop the blades faster??? The crank looks tight but could be something simple.

Jstpssng · Jul 2, 2019

Something doesn't sound right, you have a knock while it's turning over. You will probably need to have it taken apart to find out what's going on. I'm not sure how the shop could give you an estimate without knowing what's wrong with it.

DJ54 · Jul 2, 2019

It sounds as though the automatic compression release mechanism has broken. If that has a Briggs & Stratton OHV engine, you can do a search, and see that they've had a lot of problems with them breaking. It works off the crankshaft, and is a centrifugal type mechanism that holds a valve partially open until it starts, then centrifugal force will disengage it.

Instead of building a high torque starter to turn those engines past that much compression, they went with this, and is causing lots of problems for consumers.

If you can find the model number of the engine, possibly on the side of the valve cover, you can do a Google search for that model's compression release. For as much trouble as they are having with them, seems there ought to be a recall on them, and made to fix it. Then, maybe they'd go back to the drawing board, and once again build a dependable engine,like in years gone by. Likely done to compete with foreign competition.

I have no idea what it will cost to repair, now that is has gone this far, but will definitely need to be torn down,and see what the damage is.

tomplum · Jul 2, 2019

If the valve lash is set correctly then yes the compression release on the CAMSHAFT has failed. When they are caught early enough, there is about a 15% chance that other damage has been done by parts flying off. Run longer it's anyone's guess. Either have it torn down or replace the engine if the rockers already have been inspected and valve lash has been verified

thepumpguysc · Jul 2, 2019

Drag it back to the neighbors house & tell'm u want your money back.. hahaha
Go to harbor freight & pick up a 20 hp engine for 200.00.. {LESS if u have a coupon}..
{don't quote me on the price}