JD LX178 blowing black smoke

[The_Eric]

Hadn’t considered that as an option. Is the dropped valve due to a blown head gasket? Or could there other problems that are hidden?

It is not.

Which valve is that? I'm assuming the intake valve?

Most likely the valve is trashed, but it could be worth inspecting the stem and keepers and trying to reassemble and run it. Maybe, just maybe you've won the proverbial lottery and it'll be fine.

 

[Lawnman23]

Myself, I would pull the rocker pin and remove the rockers and then pull that intake pushrod and check for straightness. Compare against the exhaust if need be. The valve springs are pretty soft and your can just push down on the retainer and slide to the open slot to remove.

Thankfully, being a vertical shaft engine, the valve didn't drop into the cylinder and cause a mess of issues. If you are feeling sparky/capable, I would want to pull the head just to inspect and replace gaskets. This would also allow you to check the seat and inspect any other issues.

Seeing the intake valve issue, my hunch is that your initial black smoke issue(too much fuel) was/is just due to that cylinder not firing due to 0 compression from the open/loose valve happening.

 

[jsean]

Thanks for the suggestion guys. I’ve never done engine work before - if I take the jam nut off, I’ll be able to pull the rocker pin out?

Is there any way to verify the valves without pulling heads?

At this point, I’m wondering if I shouldn’t try and find an older GT225 or GT235 as a backup mower while I fix this one up?

 

[Lawnman23]

Thanks for the suggestion guys. I’ve never done engine work before - if I take the jam nut off, I’ll be able to pull the rocker pin out?

Is there any way to verify the valves without pulling heads?

At this point, I’m wondering if I shouldn’t try and find an older GT225 or GT235 as a backup mower while I fix this one up?

You dont need to touch the adjustment nut, just need to remove the snap ring from the pin.



The first part of this video shows the process, don’t worry about the rest of his valve seal stuff.

The valve should be fine as long as it didn’t get kissy face with the piston. You will be able to slide the valve in and out of the guide slightly once the spring and retainer are off. It should move freely but not stiff or super loose. Just be careful you don’t push it down into the cylinder, can rotate the piston to TDC to keep that from happening as well.

 

[Lawnman23]

At this point, I’m wondering if I shouldn’t try and find an older GT225 or GT235 as a backup mower while I fix this one up?

Much like auto mechanics, it’s always good to have a backup for those times…

It’s up to you, depending how fast you need this back up and running. It’s a good learning experience and worth taking you time on.

 

[SHOZ]

My used head came with the valves in it.

JOHN DEERE LX178 ENGINE CYLINDER HEAD M96729
Opens in a new window or tab

Pre-Owned

 

[jsean]

You dont need to touch the adjustment nut, just need to remove the snap ring from the pin.



The first part of this video shows the process, don’t worry about the rest of his valve seal stuff.

The valve should be fine as long as it didn’t get kissy face with the piston. You will be able to slide the valve in and out of the guide slightly once the spring and retainer are off. It should move freely but not stiff or super loose. Just be careful you don’t push it down into the cylinder, can rotate the piston to TDC to keep that from happening as well.

Thank you for the video! It’s going to be a few weeks before I’m able to get back to the mower. Good point about keeping it at TDC - I’m admittedly a bit nervous, having never done detailed engine work like this before.

 

[jsean]

Much like auto mechanics, it’s always good to have a backup for those times…

It’s up to you, depending how fast you need this back up and running. It’s a good learning experience and worth taking you time on.

I ended up purchasing a GT245 . The LX178 assuming is fixable will either be a backup mower or get sold on Marketplace.

 

[jsean]

My used head came with the valves in it.

JOHN DEERE LX178 ENGINE CYLINDER HEAD M96729
Opens in a new window or tab

Pre-Owned

I have this on my watch list. Going to attempt to pull the pin out first. Assuming I make a mess of it, these will be my backup along with a new head gasket. At that point, I might even throw on a new water pump.

 

[jsean]

So I spent a little time on the LX178. Push rod is nice and straight. This engine doesn’t have valve keepers, instead Kawasaki uses a notch on the spring seat that is used for installation and then it gets centered. Once centered, the OD of the valve is larger than the ID of the spring seat keeping it all in place.

I pulled the rocker arm off to inspect it and it looks good too. Except I can’t figure out how to get the darn snap right back - any suggestions? My existing snap ring pliers are too bulky and ain’t cutting it.

Bad news is that the top valve is really really bad to pull in and out, even with repeat PB blaster and 5w40 applications. Using my fingers I can’t get it to rotate or move in/out at all. Makes me think that valve is toast.

Any suggestions on how to verify that piston isn’t shot before tearing the heads apart?

 

[Lawnman23]

If you pull the plug, you can rotate the piston up and inspect with a bright flashlight. If the valve hit it, you will see an indentation mark. Carbon and all that is normal.

For the stuck valve, soak it as much as you can and then tap on it with a brass or wooden dowel and a hammer. Just tap it a bit, try to spin it, re soak it, keep repeating.

As far as the snap ring goes, if you can use your pliers to start it, you can push it on the rest of the way till it snaps in. Spin it around to make sure it’s in the groove straight.