Model 128M05-0026-F1 with no compression.

[flyhalhl@gmail.co.]

Our Toro mower with this engine started first pull after the winter. Ran fine for first lawn cut. Put mower on its side to clean under deck then as I usually do tried a restart. It wouldn't start so put away figuring probably just flooded. Got it out the other day and it wouldn't start. Pulled plug and it was wet with gas. Checked spark and that was good. After a few more tries I took off air cleaner and blocked the choke open and the engine fired up straight away. Ran perfectly for an hour of lawn mowing. Got it out the next day to finish and it wouldn't start. Blocked open choke and wouldn't start. Occasional loud bang out of the muffler as I pulled it over. Finally did a compression test and there was absolutely no compression. I pulled off the cylinder head suspecting a stuck valve but both are moving freely and I can rotate both valves with my fingers. They both seem to fully close. Is it possible that the valve timing is way off. I'm not familiar with the internals of this engine. Is it possible for that to happen very suddenly like this? Any other ideas?

Check the valve lift. Should be around 3

OK so I blame not spotting a slightly opened exhaust valve on my 77 yr old eyesight. Need cataract surgery. I measured the clearances and the intake was .007, the exhaust a whopping .030 Yes it was stuck open a bit. I have it freed up now using carb cleaner. Any suggestions for anything else to spray on the valve stem to help prevent it doing this trick again?

They should be removed and a proper size reamer used on valve guides. Guides build up deposits so diameter shrinks and valves then sieze. Even 7 thousanths is slightly high. Flat heads have larger clearance than the newer overhead types.

 

[StarTech]

They should be removed and a proper size reamer used on valve guides. Guides build up deposits so diameter shrinks and valves then sieze. Even 7 thousanths is slightly high. Flat heads have larger clearance than the newer overhead types.

Valve clearance on this engine are

Intake Valve	.005-.007 in (.13-.18 mm)
Exhaust Valve	.007-.009 in (.18-.23 mm)

As for the valve guides the deposits are usually on the valve stems and not the guides. The exhaust valve does have a replaceable valve guide. What can happen because of stems sticking in the guides is the valve guides can move.

Now the OP should need the 1/4 valve repair tool set to the do this replacement and reaming; although, these Sintered guides seldom need reaming.

 

[mikosh6]

Thought I would add a final post about my mower issue. After leaving the mower for a week it wouldn't start again after freeing the exhaust valve with choke cleaner. I removed the plug and the exhaust valve is visible. I rotated the crank to the point where the vavlve should be closed and gently tapped the valve down on its seat with a piece of wooden dowel. Tried starting and the engine fired up right away. I purchased some Seafoam, took out the plug, rotated the crank shaft until the exhaust valve opened fully, then sprayed a Seafoam behind the valve where it would land on the stem. Rotated crank and tapped the valve down with the dowel; repeated this about 4 times. Replaced the plug and left the mower for a week before firing it up. It's now been starting and running fine for over a month so I'm happy with that. If it does have the issue again down the road this will be the first thing I try. Hope this will help someone else down the road.

 

[slomo]

Now you guys need to guess what caused this to happen in the first place.

 

[slomo]

I would try seafoam in the gas and maybe some in the oil, if it's OK to put in the oil.
I've had amazing success with Seafoam in gas when experiencing carb issues.

Seafoam is nothing but a solvent. Which when placed in the oil, just thins the viscosity way down. Depending on how much was used could be worse. Hot running air cooled engines. See where this is going? So your SAE 30W oil just became an SAE 20 or less.

Fix the valve and guide clearance issue. Polish the valve stem and clean up the tappet end if needed. Use some gun bore brushes and solvent to free up the guide. Most likely tipping the mower cause oil to get where it doesn't belong. Another reason to get a hand or electric powered oil evac pump. Stop tipping mowers over. Many don't know what side to tip and if tipped are super hard to start. Get with the times.

 

[mikosh6]

If you read my post you'd see that the Seafoam went in behind the valve onto the stem ONLY to use it's solvent properties. Nothing added to the oil. Yes the motor shroud was taken off and all was clean, as you'll see in an earlier post I replaced the head gasket.

 

[slomo]

If you read my post you'd see that the Seafoam went in behind the valve onto the stem ONLY to use it's solvent properties. Nothing added to the oil. Yes the motor shroud was taken off and all was clean, as you'll see in an earlier post I replaced the head gasket.

I read that. Nothing added to the oil. I was just stating the obvious about seafoam snake oil.