Briggs 500 Series - Interesting troubleshooting case for the pros. help needed.

[motormonkey]

Polaraco,

I made sure the valve guides were extremely clean, then I oiled the valve stem put it back in and they moved like new.

the valves currently are functioning when I move the flywheel.

thanks for the tip on sand / grease.

I was going to say that. Thanks

When you put the valve back in the head, did slide up and down OK

Did you put some oil on the valve stem when you put it back in?

Poor mans valve grinding compound. Sand and grease. If it's an over head valve, you can use a electric drill. There's a 62 Chrysler 413 running around for 10 years now with that done to the heads.

 

[motormonkey]

hsherm,

Here is the new video for opinions on timing before anything else!

Thanks!

Thanks for sharing the video! I just watched it a few times (actually, quite a few times), and noticed a couple of things. The timing seems to be off by one "notch". (degree?) For example, the exhaust valve starts to open just before the piston reaches Bottom Dead Center (B.D.C), allowing for air and oil to be drawn into the combustion chamber. (The chamber acts as a vacuum at this point due to the combustion.) This then throws off the intake valve by the same amount; thereby lessening the amount of fuel that can be drawn in. I also noticed a slight amount of oil in the piston cylinder. This could be caused by bad rings, but it's more than likely caused by the "vacuum" effect drawing in air and oil through the exhaust port due to the exhaust valve opening before B.D.C.
It's been awhile since I've actually worked on small engines (mainly due to health reasons), so I'm making these observations from memory.
I hope this helps.

 

[Polaraco]

I'm not is the position to watch the video right now, but something came to me earlier today.

Maybe the valve spring is weak. Or as said, you're not getting lubrication into the stem. Maybe the guide is worn so that the valve jams. (Key word there is Maybe) Does the valve have slop in the guide?

In big motors, a bad guide can cause a misfire. The valve will be sluggish and a small amount the vacuum is lost, drawing less fuel/air. Sort of like that. But that's a multi cylinder engine. I would imagine the principle is the same.

If it's not getting oil into the spring chamber, maybe the oil slinger is broken in the crankcase. (Do they still use those things?)

Don't mind me, I'm in the guessing mode with out it in my hands.

 

[motormonkey]

Polaraco,

Process of elimination is a good thing so no worries.

Yes they still use oil slingers, in this case instead of it being on the end of the piston cap it's a gear mechanism that rides on the camshaft gear.
yes it's getting oil. I think the whole problem boiled down to the mower having set for a long time and getting shellac from the old gas (ethanol perhaps) and sticking the valve.
The problem I was having was that I could pull start it but it ran so slow, that I could actually speed it up with the pull rope if I pulled in time with it every 1 - 2 seconds. which tells me it's not getting the compression to get up to speed I think.

I have a new head gasket for it, but I am debating tearing it down to verify the timing again before I put the new head gasket on because user: hsherm made the comment that my timing might possibly be off by 1 tooth (the matching up of the dots on the cam and the crank.)

I know I don't need to take the head off to be able to tear it down to the crank, but if I need/want to take the valves out again and i've already put the head gasket on I don't want to risk ruining it because I had to get it hand made.

Cheers and as always, I always thank everyone for their input!

I'm not is the position to watch the video right now, but something came to me earlier today.

Maybe the valve spring is weak. Or as said, you're not getting lubrication into the stem. Maybe the guide is worn so that the valve jams. (Key word there is Maybe) Does the valve have slop in the guide?

In big motors, a bad guide can cause a misfire. The valve will be sluggish and a small amount the vacuum is lost, drawing less fuel/air. Sort of like that. But that's a multi cylinder engine. I would imagine the principle is the same.

If it's not getting oil into the spring chamber, maybe the oil slinger is broken in the crankcase. (Do they still use those things?)

Don't mind me, I'm in the guessing mode with out it in my hands.

 

[motormonkey]

motoman,

You hit the head on the nail, I was re-checking everything and this appeared....
Though this cam is not keyed like the intek cam it is pressed on... so when the valve stuck causing the engine to "knock" when pulling recoil was like putting the cam shaft in between 2 pairs of pliers.
the camshaft is one set of pliers.. and the stuck valve another... not allowing the cam to lift the lifter when needed it had no where to go but to break free when trying to go over the cam lifter.

Motor, Reread your original description...When the Intek cam was replaced I had to press off the drive gear from the cam. I don't remember exactly, but it must have been keyed. Could your cam have somehow sheared the cam drive gear key. So depending on heat the gear is spun outside the cam , making an index sound. Then when heat/cold allows the cam operates the valves, but out of time??:confused2: