STICKING VALVES(problem found)maybe

[Rick Prentice]

I need some help from the experts, PLEASE. This is the second time in less than a month this has happened.

A little history. About a month ago I used the Cub for about half a day cutting wood. It ran perfect. I shut it off for the evening. The next day when I tried to start it, it spun over really fast like there wasn't any compression. I checked things out and discovered at least one valve in every cylinder was stuck open

I removed the hood and the side valve cover. I then removed the spark plugs. I kept squirting the valves with Kroil and kept tapping them up and down with a blunt punch until they finally started to work like they should. Put everything back together and it fired right up and purred like a kitten. I parked it under the lean-to with the others.

Today, I needed to use this Cub again. Turned the fuel on, hooked up the battery, pulled the starter rod, and zing. It was doing the same thing again, valves stuck in every cylinder.

I just don't get it. What would cause the valves to stick? Is there possibly an oil issue? The last time I freed them up, it ran great the rest of the day.
I plan to remove the hood again and check things out. I don't want to do this every time I want to use the dumb thing.

Help Please,

Rick

[Donny M]

Rick,

What's the temperature out Could it be moisture in the oil and it's freezing
Weak springs could also be a cause

[Bigdog]

It's possible that there may be some slight scoring of the valves. As Donny suggested, moisture may be part of the problem. Have you added any Marvel Mystery Oil to your gas tank. A few ounces per tankful works well.

[Rick Prentice]

Hi Donny. Don't think it's the temperature. Last month it was about 65-70 degrees, and today was near 50. There's no signs of condensation under the valve cover.

And I remember last month that the stuck valves were really tight. It took alittle bit to free them up. Don't think it's a spring issue.

Rick

[rondellh]

Rick, I would remove the intake/exhaust manifold and and get a good look at the stems above the guides. You may have a buildup of carbon or rust. You should be able to get in there with a small wire brush and do some cleaning. Plus it's alot easier to spray the stems with penetrant and work them up and down.



Rondell

[Boss Hog]

I am thinking it is an oil problem. Or an unleaded gas isue. If it was getting enough oil after you freed them up the first time it shouldn't have stuck again unless an oil starvation problem. If it was running real lean
nah gat to be the oil
David

[BigBill]

Like i said before I put a little two stroke mix in the tank every so often it acts like the old Mobil upper lube it lubes the valves, valve seats and it keeps the piston rings free too. I may puff a little blue smoke when its choked but after it clears its smokeless except for the very light blue color in the fuel bowel but it keeps her running free all the time. You might say my cub is on laxitives. I run all my fourstroke equipment with some two stroke added once in a while I don't do it all the time. It really saved my log splitter engine for a lot of years it never wore out. The only drawback is once a year I changed the spark plugs they do foul sometimes from the two stroke but not that often if you run it for a while it will clean the plugs on its own. Those little spark plug sand blasters come in handy just make sure you wash the plugs clean of all the sand blast grit after.

[Lurker Carl]

I have a Gravely that did the same thing. No compression until I removed the head and PB Blastered and fiddled with the stuck exhaust valve. Then it would start and run like a champ. Until the next time. After messing with it for most of last year, I took it apart this past spring. There was a varnish-like coating on the exhaust valve stem. I think that coating was oil that ended up on the exhaust valve stem upon shut down and cooked into glue as the valve cooled. I cleaned the valve stem and guide - haven't had it repeat through out the summer.

[Eugene]

This is certainly unusual. Once you get the valves freed up they usually stay that way.

Which valves are sticking? Intake, exhaust or some, or all?

1) Suggest getting the valves free again. Add some of the upper cylinder lubricant stuff designed to free up valves and lifters to the gas - from the auto parts store - the whole container. Start engine and let run for an hour. If this works add a bit of upper cylinder lub every 3 or 4 months to the fuel.

2) Add a bit of oil to the gas every once in a while. I dump the end of day 2 cycle fuel in the Cub's tank.

3) Change the oil. Change brands of oil? Add Seafoam to the oil at the oil change.

4a) If none of the above work and it's the exhaust valves sticking. Set the tractor so that the engine is level. Remove the sparks. Pour slowly 1 quart of solvent down the exhaust pipe. Let set for a couple of hours. Rotate the engine 8 or 10 revolutions by hand. Add another cup of solvent. Let set overnight.

4b) Intake valves sticking. Remove the carburator. Manufacturer a plate and gasket to block off the manifold intake. #1 cylinder on TDC. Rotate engine about 1/4 turn. Pour solvent into #1 cylinder until the cylinder is full. Let set for a couple of hours. Rotate the engine 8 or 10 revolutions by hand. Back to TDC plus 1/4 turn. Refill. Let set overnight.

4c) Before starting engine. Install carb. Crank engine over with the starter to blow out the solvent. Move tractor out doors. Install spark plugs.

4a,b,c. This is a flat head engine, valve in block. There is a chamber under each valve. This process will completely fill the chambers under the valves with solvent. When you rotate the engine the valves will move in the solvent.

Eugene

[Rick Prentice]

Thanks for all the ideas. With all that was said, I think I'll pull the hood again , and completely remove the valves and inspect/clean them. Then I'll drain and install fresh oil and gas, with additives. I have too much going on to be tinkering with things everytime I need it, so I'll go overboard on it this time. Hopefully that will take care of it.

I'll let you know if I discover anything.

Thanks again,
Rick

[AlanPCUBS]

Sounds like a good idea Rick. Sound Oil related to me but I m no expert. Hows the oil preasure been? you might try running it a bit without the valve cover on and see if they are lubricating. Anyway good luck and hope you get her fixed.

[Rick Prentice]

Hi Alan. The guage shows good pressure. I will definetly check the oil flow under the cover. Something just isn't up to par. It sure runs good , when it's running

Thanks,
Rick

[RustyVT]

Like Lurker, I had this problem with a Gravely. I did the take it apart and clean it move as you propose and then keep it on a diet of Marvel Mystery Oil. No problems for about the last ten years and who knows how many feet of snow (blown)!

[rondellh]

Rick, The valve guides are "splash" lubricated and the oils pump and system have little to do with them. The only factor with oil is oil level and cleanliness.
I could see a problem if their has been a history of very poor maintenance ie: oil changes. This would be easily fixed by cleaning with penetrant and working the valves and shouldn't return as yours does( you could use one of the motor flushes or additive to clean the engine internally but I personally would never do that especially on an engine without a full flow lube filter).
The route you last stated is the best in my opinion as you will be able to clean the valve stems better and the guides which can only be cleaned this way.


Rondell

[George Willer]

Rick,

Are the valves and guides new? I've had new ones stick open before the engine is ever run. They never stuck again, though.

The plot thickens!