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I was going to post this in the John Deere section but it doesn't seem anyone has posted there since last year. I hope to get some answers in here. I have googled my problem but haven't found any good answer.

I have a JD LX 176 w/ Kohler 14hp engine. Last year it didn't want to start. The engine would have to spin over for a while before it would start. It seemed to be worse when it was hot. It would also backfire out of the intake and the exhaust. I mean a really loud backfire, sounded like a shot gun.

I mis diagnosed it as a valve problem. Took the head off, lapped the valves, new head gasket, adjusted the valves and it still did the same thing. It sat all winter and today I decided to mess with it again. It started up twice and ran fine. I had the valve cover off it still so I shut it off and put it back on.

I tried to start it again and it started doing the same thing. It will spin over and will eventually backfire. I have an inline spark tester in it and it is getting spark.

I know that it is capable of running because it did it twice.

I have read it could be the flywheel key or some part of the ignition system. The coil was replaced last year but didn't make a difference.

I've been working on cars for 15 years now but these small engines seem to give me fits.

Any help would be greatly appreciated. The grass is growing and my wife is wanting to know when I'm going to fix this thing.

Any help would be greatly be appreciated.

Jason

Can you give us the Model, Spec and serial numbers for this engine. It would help us help you. Back fires on small engines are caused by bad flywheel key, too rich fuel mixture and/or valves and valve timing. From what you describe I would lean to a fuel mixture problem. Too rich. Have you tried leaning out the carb. Does it do it all the time or only on start up?

Engine code is FC420V-AS10
E/NO is FC420VA36622

It has a new carb on it from the dealer. It acts the same as it did with the old carb.

When it ran today, I choked it and it fired right up the two times. Now it won't run at all.

Would you check the spark plug right after you try to start it. Is it wet? If it is dry, my next step would be to check for a sheared fly wheel key. Keep me posted, have to go to work.

It's black. Very black.

Engine is running way to rich, flooding on start up. Have you tried starting with no choke and half throttle. Does the carb have any adjusting needles? If it does set the high speed at 1&1/4 turn out after lightly seated and the idle 1 turn out after lightly seated. Also, the float level may be set to high.

I have tried different throttle positions and they haven't made a difference. I will check the carb adjustments tomorrow.

It acts the way it did with the old carb on there too. Is there a next step after the carb adjustments?

I appreciate your help.

Have you checked the flywheel key?

I haven't checked the key. I guess that's where I'm headed next. What's the best way to pull the flywheel off? I'm sure they sell a special tool for it. It looks like I could make something out of square stock steel, drill/tap the center and drill two holes to put bolts through.

When you shut it down, are you letting it idle first? If so, you run the risk of backfiring on shutdown and potentially blowing out the muffler. When you shut down, if the mower is at idle, you still have fuel flow, which then flows down into the engine setting up a beautiful potential for backfire.

On shutdown, try running at full throttle, then turn off the key.

Check to see if this engine has an ignitor on it. It is what controls the fine tuning of the spark timing. Like what a cars computer uses the crank and cam sensors to do. If it goes bad, you can have perfect spark but could be off a few degrees and backfire or off a lot more and only crank over. That could also explain the black plug, late or early spark will be the same as a weak spark.

It will have a single spade terminal on the bottom with one wire going to it. The unit itself is only about an inch square and a quarter inch think. It would be mounted on the engine shroud providing the ground.

Don't know how handy you are, but pulling the flywheel is not that hard. Once you have the nut off screw it back on until it it just flush with t.he end of the crank. Now if you have a buddy it will help. Take two large screwdrivers and pry up on the flywheel. Careful that you have a good solid pry points. Strike down hard on the nut and crank squarely with a big hammer. IF YOU DO NOT HIT IT SQUARELY YOU COULD DAMAGE THE CRANK. BIG $$$$$$ IF YOU DAMAGE THE THREADS. It should pop loose. If you are not comfortable doing this, don't try. Also, if you do find a parochially sheared key buy a new one, don't try to make a new one!! Don't forget to torque the nut when you reassemble or you will shear the key when you try to start the engine.

I appreciate everyones replies. I pulled the flywheel off tonight and the key is not damaged. However the entire underside of the flywheel is incased in dirt. It's caked on. It fills the gap between the inside of the flywheel to the pickup thats bolted to the engine block.

It can't be helping anything but do you think it would cause my problem? Is there anything I should check while the flywheel is off.

Also what is the torque spec for the flywheel nut?

I believe the torque is 45 foot pounds. Does your carb have a fuel shut off on the bottom of the carb? If it does, take it out and check it. How? Attach the wire the positive terminal of a power source and touch the negative to the case. You should see the shut off close.

I got it back together and it started. I thought I had fixed it. Let it run for about 15 minutes and it wouldn't restart. I shot some starting fluid in it and it wouldn't fire. Iced the module down on the side of the engine and it fired up. I mowed with it for about an hour. Shut it off and it wouldn't restart. Going to try and ice the module down again here in a bit.

I'm having an issue with the hydrostatic drive. I will probably have to start another thread about that.

Actually I think I just need to replace the belt that goes to the hydrostatic unit. It's wore out. It starts slipping when you go up a hill or try to press the accelerator all the way down. It will move fine as long as you don't press the accelerator down too far.

I checked the fuel shut off like you suggested. After it ran for a while, then wouldn't restart I checked the plug. It was dry. It's getting spark but when I shot starting fluid in it, it wouldn't start either.

When it does start it runs great. Is there anything besides the module I should be looking at? I don't know if I have/had more than one problem or not.

did you ever get this fixed? if so what was the cause. i seem to have the same problem.
when i shut it down it backfired, has not started since, using charger in start mode it can try starting it till the cows come home , tried starting fluid, check fuel filter.

backfires when i vary the throttle during starting procedure.

it would be nice if some one would finish this post. there is no answer as to what the problem was. I am having the same problem. almost certain it is an electrical problem. it will start and keeps running well ocasionally but mostly just turns over and backfires. I have done every thing this dude has done and it just turns over. maybe its just a piece of junk like every other vehicle:frown: with computers and circuit boards on them. :frown:

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.

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

: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?

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

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.

LilJayV10 said:

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

Click to expand...

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.

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

LilJayV10 said:

... 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. ...

Click to expand...

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 said:

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.

Click to expand...

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!