very strange mower problem
 

I was working on a friends mower, 13.5 BS engine.
as soon as I cranked it I could tell it no compression.
turns out BOTH in and out valves were too tight and not closing.
there was also a bolt broken off on the valve cover.
now the mower is not that old/not much use and it is owned since new buy a mother and daughter. she swears no one else has worked on it.

the million dollar question, how the heck did BOTH valve get so tight they wont close.
I am not talking just a little too tight, I had to turn the adjuster a good bit.

I can get it to fire but the needle valve in the carb is bad and it is now flooding.

Only thing I can think of is if the adjusters were the cause and you had to back them off, the lock nuts weren't tight -OR- if there aren't lock nuts it would have to have interference threads to keep them from turn during operation, they weren't machined properly........

Could the cam bearings have worn on the block side from the chain being too tight? Hail Mary

Ever change the oil? Air filter plugged? No oil could wipe the cam.

Interesting issue

Crate engine.

Interesting problem. I'm guessing low oil. Could the valve cover have leaked as a result of the missing bolt?

Find a Briggs and stratton/small engine forum. Some of the BS engines had cam failures which symptoms mimick valve adjustment issues.

This got me looking at the internet which mentioned specifically 31 series engines.
Guess what engine I have?
31 series.

THANKS A LOT!!!!!

first thing I did was check oil, a woman owns it...it was clean.

mower is an 09 and has not run in 3 years. it still looks new.
SOMEONE had to have adjusted them. the broken screw on the valve cover??? not from the factory.....I hope.

cam wear would loosen them up. bent push rod would loosen them up.

rocker adjusters were tight

It runs for about 10 sec, bad float needle, and it sounds fine. no knocking, no rattles.

I just thought this was very odd and had to share.


it seems like B&S is wasting $$$. there are SO many variations of basically the same engine.
its not like they are making improvements. all the $$ just in different carbs, that cant be practical. how many do you need for a 13hp engine??

I think an equally puzzling question would be how a bolt spontaneously broke on the valve cover. My diagnosis is the mother may swear no one has "worked" on it, but she is mistaken.

If the valve seats, or valve faces were experiencing some serious wear, the valves would retreat up into the head, making them tight .

Camshaft has compression release system built in. These often go bad....

Compression release on both intake and exhaust?
I don't think that's the problem here. Somebody's been into this thing - somebody who didn't know what they were doing.

^^^
Is the valve cover crushed where the broken bolt is?

that's the only other explanation I could come up with . the mower looks like it has not been used much though. I would hate to think that is it with so low time on it.

I have heard about that compression release but don't know anything about it.

I don't know why she would not tell me someone else worked on it.
I found the porcelain broken on the spark plug. not sure if it would keep it from running but I suspect it did and someone tried to fix it and adjusted the valves.
seems pretty odd they would try to adjust valves and not check the plug though.

I suspect this will go down with the Kennedy assassination mystery

Did it run the last time she tried to start it 3 years ago?

no, that's why I have it.
the story is a little sketchy. supposedly she went to start it and it would not start.