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I have a Toro 75212 with a Toro branded 24.5 VTwin engine. I noticed it was bogging under PTO and found that one of the spark plugs wasn't running the engine. I changed oil, filter, air filter, and both spark plugs. Pulled wire off RIGHT spark plug and it runs. Replace and remove wire from LEFT spark plug and it won't start. I pulled the valve cover off the right side and found oil, not a lot but enough to run out onto the floor. Is this normal? Also, the valve cover gasket was/is torn. I don't know if it was blown before removal or when I opened it. I'll be replacing but not sure if it would contribute, I figure it would be the head gasket that would allow oil in. I haven't done a compression check yet as I'm awaiting the tool. Any guidance?

Seems your left coil must be bad, some oil in valve cover is normal. be sure and replace gasket to clean surface. Could be a bad plug, or a grounded kill wire on that coil. can get a spark tester cheap.

TXJosh said:

I have a Toro 75212 with a Toro branded 24.5 VTwin engine. I noticed it was bogging under PTO and found that one of the spark plugs wasn't running the engine. I changed oil, filter, air filter, and both spark plugs. Pulled wire off left spark plug and it runs. Replace and remove wire from right spark plug and it won't start. I pulled the valve cover off the right side and found oil, not a lot but enough to run out onto the floor. Is this normal? Also, the valve cover gasket was/is torn. I don't know if it was blown before removal or when I opened it. I'll be replacing but not sure if it would contribute, I figure it would be the head gasket that would allow oil in. I haven't done a compression check yet as I'm awaiting the tool. Any guidance?

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I may be misunderstanding you but it sounds as if you're surprised that oil was found under the valve cover. This is NORMAL.

Your own diagnosis indicates the bad cylinder is the LEFT cylinder, not the right.

Take the valve cover off the left cylinder and rotate the engine by hand through at least two full turns and check to see that the valves function normally. Check for bent pushrods.

get an inline spark tester and fit it to the bad left side.. see if you have spark.

cpurvis said:

I may be misunderstanding you but it sounds as if you're surprised that oil was found under the valve cover. This is NORMAL.

Your own diagnosis indicates the bad cylinder is the LEFT cylinder, not the right.

Take the valve cover off the left cylinder and rotate the engine by hand through at least two full turns and check to see that the valves function normally. Check for bent pushrods.

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Thanks for the pointers guys... sorry about the mis-type. I edited my original post to correct the good and bad side. I wasn't sure if oil should be in the cover, just wanted to verify. Pulled both sides and they matched. Both sides look the same as far as rods, amount of oil, etc.
The left is the good side as it runs with that spark plug. The right spark plug won't run it alone. I used an inline spark tester and both show consistent spark. I also got a compression tester on it. Pulled the plugs off both sparks, tested the good side "left" and it showed 180. Tested right side and it too showed 180. The good side spark was already a bit black and wet, the bad side had a bit of black carbon on it but was dry. I'm stumped. I have next to no engine experience. I can change the oil and watch Youtube vids...

Swap the plugs as a spark tester can show even with a bad plug. Swapping would indicate a bad plug if the problem moves to the other cylinder.

And try it with the kill wires removed from both coils
Not sure if they use embedded diodes or wired in diodes to prevent one coil causing a misfire in the other

bertsmobile1 said:

And try it with the kill wires removed from both coils
Not sure if they use embedded diodes or wired in diodes to prevent one coil causing a misfire in the other

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Any guidance on this? Not sure how to locate or even determine if/how many/where etc they would be on this motor.

Take the plastic cover off the engine
Follow the spark plug wires back to the coils
On each one there will be a thin wire pushed onto a tab, usually underneath
Pull them off & tie back out of the way so they don't get chopped up by the flywheel teeth
Put the plasitc cover back on
Put a pait of good insulated pliers in your pocket just in case you have to pull the spark plug wires off to stop the engine
Go mow
PRoblem goes away = wiring fault
Problem stays = fuel , valve or timing fault .
That is how a novice diagnoses a problem, eliminate one thing at a time till the guilty party gets found out.

bertsmobile1 said:

Take the plastic cover off the engine
Follow the spark plug wires back to the coils
On each one there will be a thin wire pushed onto a tab, usually underneath
Pull them off & tie back out of the way so they don't get chopped up by the flywheel teeth
Put the plasitc cover back on
Put a pait of good insulated pliers in your pocket just in case you have to pull the spark plug wires off to stop the engine
Go mow
PRoblem goes away = wiring fault
Problem stays = fuel , valve or timing fault .
That is how a novice diagnoses a problem, eliminate one thing at a time till the guilty party gets found out.

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Thanks. I'll give that a shot!

Looks like to was a bad coil after all. I swapped the coils and the problem swapped sides. Put a new coil on last night and wa-la... runs like a champ and doesn't even need choke to start...thanks all!

Glad to hear she is running.

Now take the fan shroud off and clean each cylinder cooling fins all the way around each cylinder. This is a yearly maintenance deal in your engine manual. More if you bag or scalp in early spring. Neglect this and you are looking at engine damage later on.

Also decarbonize each cylinder. Again another couple year deal in you manual. Depends on how many hours you mow. This keeps chunks of carbon out of the bores and prevents scoring.

slomo