Stuck exhaust valve in old Gravely tractor

Tom in TN · Jul 24, 2013

I am working on a Gravely walk-behind tractor/mower for a friend of mine. It is the old "L" style tractor that was new in about 1964 or 1965.

The exhaust valve is binding badly. It will come up when I turn the engine over, but will not go back down. If I rotate the engine so that the intake valve is open, I can tap the exhaust valve back down, but it takes a pretty good tap using a piece of 2 X 4 lumber and a mallet.

I have soaked the valve stem for about four days using PB Blaster. I can turn the valve using a pair of pliers, but it turns really hard.

I've turned the engine over and tapped the valve back down into the engine about 20 times and it is still really stuck.

The mower sat outside in the rain. One of the head bolts has been twisted off and there was definite signs of rust inside the head and on the exhaust valve.

Any ideas short of pulling the cylinder and removing the valve from the block?

Thanks,

Tom in TN

El Toro · Jul 24, 2013

Squirt lots of engine oil around the stem and keep rotating the engine. The valve stem may be rusted. Hal

El Toro · Jul 24, 2013

I did that on a Kubota generator that had no compression. I pulled the head and found the exhaust valve stuck. The generator was sitting out on the street for the trash pickup. Engine started on first pull. Hal

Tom in TN · Jul 24, 2013

Thanks Hal,

That's exactly what I'm doing right now, but it seems like it should have loosened up by now. I've been spraying PB Blaster onto the stem and squirting oil also, but to no avail yet.

For now, I guess I'll keep trying the oil and see if it comes around.

Tom in TN

paul n.h. · Jul 24, 2013

try using Liquid Film on it works most of the time for me

Tom in TN · Jul 24, 2013

Paul,

Thanks for the tip. I must admit, though, I've never heard of Liquid Film. Where would I get some of that? I'm open to any and all suggestions.

Tom in TN

jeffcat · Jul 24, 2013

Another product that the truckers use is MotorCoat. I have freed up some pretty stuck stuff with it. Walmart - auto section- bottom shelf- black bottle - $26.oo a quart. Worth every penny. I use it on threads and bearings ETC. Try it. Jeffcat

El Toro · Jul 24, 2013

Some lubri-plate may help. If you have the head off I would pull the valve and take a look at it.
The stem may be rusted from water. Hal

Tom in TN · Jul 24, 2013

Thanks Hal,

Unfortunately, it's a flat head engine. To remove the valve, I'd have to pull the cylinder off the block to get access to the valve spring keeper.

If I can't get it loosened up with lubicant, it looks like I'll have to that.

Tom in TN

Tom in TN · Jul 24, 2013

Thanks Jeffcat,

There's a WalMart about 25 miles from me. If I can't get the valve loosened up pretty soon, I'll try that.

Tom in TN

wwminc · Jul 27, 2013

time for a new valve and guide.

Bret4207 · Jul 28, 2013

(quoted from post at 20:21:13 07/24/13) Thanks Hal,

Unfortunately, it's a flat head engine. To remove the valve, I'd have to pull the cylinder off the block to get access to the valve spring keeper.

If I can't get it loosened up with lubicant, it looks like I'll have to that.

Tom in TN

IIRC there's a cover that you can open to adjust the valves. Richards Lawn and Garden is the big source for old Gravely stuff in the US. There are a couple of Gravely clubs on line. I'll see if I can remember to find the shop manual and take a look for you.

Traditional Farmer · Jul 29, 2013

I've had good luck with Marvel Mystery oil freeing up stuck valves.

Bret4207 · Jul 29, 2013

On each side of the engine, under the exhaust manifold in this case, right above the crankcase is a small cover with 2 screws holding it on. That's how you access the valve keepers. IIRC you don't have to pull the head at all.

You should get the shop manual for the Gravely.

old · Jul 29, 2013

My dad had one of those a long time ago. It was common to have that happen to his and I was pulling the head off all the time due to sticking valves. It got to the point I would fill the cylinder with ATF when he parked it for any long times so that the valves would not stick. I would do that with that one. Fill till it comes out the exhaust and let it sit a few days and then check it out

johnlobb · Jul 31, 2013

I subscribe to a yahoo gravely discussion group and there are some really knowledgeable guys on there. This exact issue was discussed recently but I don"t know the fix.

Bret4207 · Aug 1, 2013

Basically what happens is the ex valve gets carboned up, maybe a little rust too and it sticks. You can usually lube them back into operating condition, but sometimes you have to pull the valve and ream or otherwise get the carbon out of the guide and off the stem. Running a little ATF or Marvel in the fuel will help some and so will making sure the timing is on and the carb isn't running rich. Considering the age of most of these engines, the Gravely design is remarkable for what it is.

Bkuz · Jan 28, 2015

It might be better for you to remove manifold and the valve spring cover and the keepers - then pull valve - guide might come out with it - pry bars on valve and tap top of jug with mallet and block of wood- last resort stuff- it did one just like that last year-
And then replace guide and valve -

Stuck exhaust valve in old Gravely tractor

Tom in TN

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