Snapped pushrod

D

DRWDRW

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I have a small riding mower with B&S single-cylinder OHV engine, which I've owned from new (about 15 years).

A year or two ago it developed a problem that seemed insignificant - the engine would turn over slowly before firing, almost as though the starter motor was tired. Nothing went wrong until one day, during use, the engine simply cut out. I took it apart and found the alloy pushrod had bent and snapped (not sure which came first).

I removed the cylinder head, inspected the engine, found nothing much wrong, fitted a new pushrod and plastic guide, put it all back together and did another season's work without issue.

This year, I dragged the mower out of hibernation, used it for half an hour and then exactly the same happened - the engine stopped, and the new pushrod has snapped.

Does anything look amiss in here, or has the guide pushed up?

Thanks.
 

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Boudreaux In Eunice La.

Boudreaux In Eunice La.

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That head looks different than all the ones I have seen...... It does look like it is out of place though...... Try to find one like it and compare it ..... Or go to a shop and get a second opinion...

It won't be long before someone else will chime in.............
 
tom3

tom3

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Brother in law had a Poulan rider with a Briggs OHV engine. Lost power a couple months after he bought it, took to dealer, loose valve adjustment. Tech told him those needed adjusted every year on those mowers. He didn't listen, next year the engine quit, push rod broke and jammed the crankshaft. So I guess just get used to adjusting the valves on a regular basis? Or maybe put a jam nut on the rocker adj. nut.
 
D

DRWDRW

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tom3 said:
Brother in law had a Poulan rider with a Briggs OHV engine. Lost power a couple months after he bought it, took to dealer, loose valve adjustment. Tech told him those needed adjusted every year on those mowers. He didn't listen, next year the engine quit, push rod broke and jammed the crankshaft. So I guess just get used to adjusting the valves on a regular basis? Or maybe put a jam nut on the rocker adj. nut.
Click to expand...

Mine is a British-market equivalent of the Poulan, so I guess it's the same engine.

I never adjusted the valves for the first ten-or-so years but lately have checked them regularly.

Something I forgot to mention was that when the engine stopped this time, the valve clearances seemed to have closed up - so much that, with a new pushrod in place, there's no gap for the shim.
 
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ILENGINE

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Aluminum pushrod is getting abrasive wear. Something is contaminating the oil causing it to war the guide and pushrod. What does the oil look like when you change it. Possible partially blown head gasket causing carbon deposits in the oil. You can also use the steel rod instead of the aluminum rod if you want, and will not cause any issue other than will take longer to wear thin.
 
D

DRWDRW

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ILENGINE said:
Aluminum pushrod is getting abrasive wear. Something is contaminating the oil causing it to war the guide and pushrod. What does the oil look like when you change it. Possible partially blown head gasket causing carbon deposits in the oil. You can also use the steel rod instead of the aluminum rod if you want, and will not cause any issue other than will take longer to wear thin.
Click to expand...

Head gasket looks fine (was renewed with the last pushrod) and the oil appears (looks and smells) unremarkable.

I'll certainly try a steel rod instead - thanks.
 
cpurvis

cpurvis

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DRWDRW said:
Mine is a British-market equivalent of the Poulan, so I guess it's the same engine.

I never adjusted the valves for the first ten-or-so years but lately have checked them regularly.

Something I forgot to mention was that when the engine stopped this time, the valve clearances seemed to have closed up - so much that, with a new pushrod in place, there's no gap for the shim.
Click to expand...

That's usually a sign of the valve receding into the head. In some repair manual, there should be a maximum installed height for the valve spring.
 
Fish

Fish

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The collet keeper on the exhaust valve looks boogered up,
At first glance.

I'll re-read this all again.
 
Fish

Fish

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So which valve's pushrod is dying?
 
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bertsmobile1

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Measure the height of the valve guides, they should be the same.
What is happening is the pushrod is dropping into the engine then the cam comes around & breaks it
The push rods jump off because the valve lash gets too big
The plastic guide that is there need to be replaced , where is the other one ?
Do not reuse the old head gasket.
There is way too much oil in your head so most likely the valve stem oil seal on the inlet valve is gone ( none on the exhaust ).
Were both of the lash caps on the end of the valve stems ?
If one dropped off
1) it will be in the engine somewhere
2) puts the rocker at an angle where it can hit the valve spring which can cause the push rod to drop off.
 
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