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poulan pro riding mower cut out while mowing. Would not restart. Made loud popping noise when turning over.
checked compress in both cylinders. 30lbs in left and plug covered in wet oil. 120lbs in right cylinder, plug normal.
suspect head gasket, our local repair shop on vacation this week

Sounds like it
Remove the bad plug and see if it starts
Remember to ground the plug lead

bertsmobile1 said:

Sounds like it
Remove the bad plug and see if it starts
Remember to ground the plug lead

Click to expand...

turns over, doesn’t start but doesn’t cut out like it did when trying to start it with the plug in

Or my other thought is one of the heads has overheated and dropped the valve seat and is holding that valve open. Should be easy to find because the push rod will be laying loose if it just happened.

Took valve cover off offending cylinder, the aluminum push rod fell out in two pieces. There was no other push rod.

Where's the exhaust pusher rod at?

In the crank case. These engines are noted to do this. Have a friend that says he has an engine with 3 in the crank case and still running. I got one that had one in the crank case took it apart and found the steel push rod laying on top of the cam gear bent like a paper clip. It did no damage to the rest of the engine. Put in a new push rod and engine runs fine. Still going.

Was able to remove bent pusher rod from crankcase with magnet. Replaced cylinder head and rods. Ran rough when starting. Checked rods in opposite head, both bent. Replaced them. Engine runs very smoothly.
however…one final problem…engine turns over most of the time but sometimes i turn the key, the engine begins to spin but stops abruptly. at This point the flywheel is hard to turn by hand but once it gets past the top of the compression stroke the engine will start with the starter.

My engine is a Briggs and stratton 441777 0726 e1.

make sure your valve clearance is set properly

All four valves were set to .005 when the pushrods were recently replaced. Upon rechecking all four are still at .005.
thx

How much does my methodology affect the settings? I saw two methods of setting these. One, and what I did was, bring the cylinder to top dead center, both valves closed. Set both at the same time. The other method was to bring the cylinder to top dead center but advance the flywheel an additional quarter of an inch. Did I set them with the piston in the wrong place?

I can't recall exactly why the recommendation is to move the piston 1/4" past TDC,
I use the OVOOVC method with no comebacks or trouble.
One Valve Open, One Valve Closed, adjust the valve that is closed.

Scrubcadet10 said:

I can't recall exactly why the recommendation is to move the piston 1/4" past TDC,
I use the OVOOVC method with no comebacks or trouble.
One Valve Open, One Valve Closed, adjust the valve that is closed.

Click to expand...

Alright. I’ll try that.
Thank you

I opened the valve covers only to find a bent exhaust pushrod. The intake rod is fine. Both of the rods on this side were replaced last week.
The rods on the opposite side were replaced two weeks ago while replacing that head. Both of those rods are fine.
I used the machine once to mow the lawn from the time of replacing all these rods to now. Machine ran fine except for the restarting problem which was the original reason to begin this thread.

Should I have replaced both heads?

Probably
Pushrods bend because the cam is pushing the push rod but the valve can not move any further
The usual reasons are a stuck valve or a slipped valve guide
Valve guides slip because the heads got way too hot and lost their temper
IF this is the case then the head is scrap metal unless you have a friend who restores motorcycles & is inclined to make & fit oversized guides fr a really nice burbon .

Now this is a sign of a bigger problem, your head is getting way too hot
While this can be operator error like running then engine at lower speeds than WFO or failing to clean the cooling fins, I have found several Kohlers that run way too lean thus way too hot requiring drilling out the main jet a TINY amount ( next size jet drill larger which is 0.0001" in my kit )

The new head arrived today. It has been replaced. the lash was set at .004 using the method prescribed.
the engine had a tough time getting past compression. This requires turning the key two or three times until it turns over. Once the engine turns over it starts right away and runs smoothly.
upon closer inspection the exhaust valve guides on both head were at least .0375” higher than the intake guides in both heads. I ran the engine slow for a couple minutes then slowly brought it to full speed then slowed it down before shutting it off. It ran smoothly through the speed changes. I did not want to run it long for fear of heat buildup.
though I’m confident taking the carburetor off I do not have the tools necessary to drill the main jet. I’ll speak to a local repair shop Monday for assistance with this.
I’m still baffled by tough starting. The camshaft on this machine is not made with a compression release built in. The “easy spin” system seems to depend on an “zero lift zone on the cam lobe” (according to “how to repair Briggs and Stratton engines”). Do I need to change the cams or can this problem be solved with the lash setting?
thank you

could the battery be weak?

i wonder, if something broke the pushrods originally could have damaged the compression relief as well>
Need to get a volt meter and check the voltage while cranking.

Kparent said:

poulan pro riding mower cut out while mowing. Would not restart. Made loud popping noise when turning over.
checked compress in both cylinders. 30lbs in left and plug covered in wet oil. 120lbs in right cylinder, plug normal.
suspect head gasket, our local repair shop on vacation this week

Click to expand...

Local repair shop on vacation in peak mowing season? You must live in Colorado or Canada. Around here, you can't even pull into the parking lot to get a mower looked at. Our mower shops are busy.

Kparent said:

All four valves were set to .005 when the pushrods were recently replaced. Upon rechecking all four are still at .005.
thx

Click to expand...

There are two top dead center conditions on a four stroke engine. You could of set the valves on the wrong stroke.

Scrubcadet10 said:

I can't recall exactly why the recommendation is to move the piston 1/4" past TDC,
I use the OVOOVC method with no comebacks or trouble.
One Valve Open, One Valve Closed, adjust the valve that is closed.

Click to expand...

That 1/4" deal is to get past the compression relief.

bertsmobile1 said:

While this can be operator error like running then engine at lower speeds than WFO or failing to clean the cooling fins

Click to expand...

Agree on this. OP is trying to fix the problem overlooking what might of caused it to begin with. Need conformation on are the cooling fins and block CLEAN. As in a shiny new engine look down to bare aluminum. Pictures of everything assist us in helping you.

Agree with sgkent. Take the battery to an auto parts shop. Have the battery load tested for free.

Agree with Scrubcadet10. Need to do voltage drop testing on the entire + and - sides of the battery, while CRANKING engine. Also make sure the ground strap is a stellar fella'. Check every cable and connection on the + and - sides. Polish every connection while you are there. Little dielectric grease is your friend here. Star grounding washers should be added.

Do you power wash this after mowing? If so that is another topic as what not to do.

Reset the lash to .006 using ovoovc method.
The engine now starts repeatedly without hesitation!
There were mice nests and caked on debris under the cover when these problems began. I cleaned it out then but I cleaned it all again more thoroughly getting between all the vanes with a plastic brush. I’ll add engine inspection and cleaning to my regular maintenance routine.
many thanks to all for your contributions in helping solve these issues!

Kparent said:

Reset the lash to .006 using ovoovc method.
The engine now starts repeatedly without hesitation!
There were mice nests and caked on debris under the cover when these problems began. I cleaned it out then but I cleaned it all again more thoroughly getting between all the vanes with a plastic brush. I’ll add engine inspection and cleaning to my regular maintenance routine.
many thanks to all for your contributions in helping solve these issues!

Click to expand...

Cleaning the cooling fins and block is a yearly to-do engine maintenance item in ALL mower engine manuals.

Dirty cooling fins is what caused this to happen. Keep the fins clean and the oil on the full mark. Easy right?