John Deere LX176 backfires, won't start

[cityfarmer]

my john deere had a shere pin on the shaft that was stripped. made the timing off. but mine would not stop. there are some good threads on how to replace it but I paid 75 bucks to let someone else fix it. you may need a air rachet and a few good friends to hold the thing to get the large nut off the top.

 

[pawl]

unfortunately if you read the thread lil jay says that it will start and run fine ocasionally but upon restart it will turn over but not start which is my case also. I took it to a mechanic and he says it has no compression, in that case it should not have started and run. it would not start either if it were a shaft key. some other threads talk about the compression release built into the valve train. I believe this could be it but not certain. could anybody tell me where this compression realease is and how it works

 

[Buckshot 1]

:smile: Seeing how that is a Kaw engine it could be a intermittent igniter trouble. As far as no fuel to the plug, is this a gravity/fuel pump system?

 

[LilJayV10]

Guy I know it's been a long time since I posted this but I wanted to give an update. The mower has sat for well over a year. I had pulled the flywheel off and cleaned under it, it was full of dried grass. I put it back together and it still wouldn't start. I had an inline spark tester on the spark plug wire to the plug. I was getting spark but it wasn't very bright. I realized that my john deer walk behind mower(that doesn't run) has the same engine as the LX176 does. I swapped out the ignition module and it still wouldn't start. The coil and plug had been replaced. As a last resort I pulled the part off that sits under the flywheel that bolts to the block. I can't remember what it's called. Put it back together and immediately saw the spark was brighter than BAM it started. It's been running for almost a month now. I have no idea what could go bad in those windings but it fixed it. I hope this helps someone in the future.

Jason

 

[EngineMan]

Good to know that she's running again, if you do remember what the part that you took off was called let us know it could help someone with the same problem.

 

[draker]

Guy I know it's been a long time since I posted this but I wanted to give an update. The mower has sat for well over a year. I had pulled the flywheel off and cleaned under it, it was full of dried grass. I put it back together and it still wouldn't start. I had an inline spark tester on the spark plug wire to the plug. I was getting spark but it wasn't very bright. I realized that my john deer walk behind mower(that doesn't run) has the same engine as the LX176 does. I swapped out the ignition module and it still wouldn't start. The coil and plug had been replaced. As a last resort I pulled the part off that sits under the flywheel that bolts to the block. I can't remember what it's called. Put it back together and immediately saw the spark was brighter than BAM it started. It's been running for almost a month now. I have no idea what could go bad in those windings but it fixed it. I hope this helps someone in the future.

Jason

Well here we are years later and I've got this exact same problem! I picked up a JD 275 with the 14hp fc420v for cheap. It had a blown motor, so I replaced it. It fired right up pretty easy and ran good. I then mowed more than half my lawn. After stopping to empty the grass catcher a few times, it was getting progressively harder to start. It would crank for a long time and massive backfires out the exhaust like the original poster says.

What I've done so far:
Pulled flywheel and checked for sheared pin, no issues.
Pulled carb and inspected, jets and float. Very clean, no issues.
Adjusted valves to .006, they were a little loose before.
Checked compression, compression was good. Actually higher than I expected it to be. I've got a service manual coming in the mail so hopefully it will show the compression specs for the fc420v.

When the mower was running, it ran fantastic! No smoke, plenty of power.

I've got a spark tester, I'll check that next.


I was happy to see the follow-up to this thread. It gave me some good idea for additional things to check.

Anyone still using these old mowers other than myself? It was too good of a deal to pass up on, even with a blown motor. Has the powerflow and grass catcher too.

 

[deckeda]

These old threads are always interesting. And popular, too, since Google keeps picking them up.

... As a last resort I pulled the part off that sits under the flywheel that bolts to the block. I can't remember what it's called. Put it back together and immediately saw the spark was brighter than BAM it started. ...

Do you mean the stator? But you didn't replace it, just removed and reinstalled (lawnmower whisperer?) I suppose the impacted grass you mentioned acted as a heat insulator and freaked it out. A stator is part of the charging system. It generates AC voltage, and the rectifier/regulator converts that to DC voltage and charges the battery. How the stator impacts ignition performance (or why it would/could) someone else will have to explain.


Random image of one:





By the way, later mowers in this series (with FC420V-DS10) incorporated the function of the igniter module into the coil.

 

[draker]

Well here we are years later and I've got this exact same problem! I picked up a JD 275 with the 14hp fc420v for cheap. It had a blown motor, so I replaced it. It fired right up pretty easy and ran good. I then mowed more than half my lawn. After stopping to empty the grass catcher a few times, it was getting progressively harder to start. It would crank for a long time and massive backfires out the exhaust like the original poster says.

I wanted to update and mention I fixed this issue and the lawn mower is running great. The issue was the coil gap was too large. I set it with a business card like many say to do. Well that's not a great idea. I set it to factory spec and it fired right up. Been running great ever since. Mowed my lawn many times!