Will an early 80's Briggs run with 50 psi?

7394 said:
Actually taking a compression test can help.
1st) a dry test.
2nd) add two squirts of oil in spark plug hole & re-test. Compression will be higher, but if it is very much higher, then valves are not the only issue. Aluminum sleeve blocks do wear easier.

What happens to the valves is they beat themselves deeper into their seats, reducing & /or elimintaing the necessary valve lash clearance, so compression drops. Fix is to remove one valve at a time & grind off a few thou as your situation needs (off the stem head) & replace & check for correct lash spec, w/ feeler gauge. This may take a couple times or so, but go easy, easier to remove a bit more, than to wish you could add some back.

My vintage MTD has a B&S L-head on it, & it still cuts decent with only 50 psi compression. Although mine is slated for replacement this season.
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Great, I am getting some good direction from everyone. Thank you!! I am enjoying my new part time hobby too. cheers!!!
 
Some engines have compression releases/exhaust dumps to make cranking easier. These will skew a compression reading.

It should crank and run on 50lbs. Probably not make any great power/torque. It's an old Briggs. Sucker might run on 5lbs.

slomo
 
slomo said:
Some engines have compression releases/exhaust dumps to make cranking easier. These will skew a compression reading.

It should crank and run on 50lbs. Probably not make any great power/torque. It's an old Briggs. Sucker might run on 5lbs.

slomo
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I got a chuckle at the 5lbs remark, thanks. Yea I guess if it isn't broken don't fix it. Looking forward to some weather where I can get her fired up, I may run a couple of tanks of sea foam through her and take it from there. cheers!!!
 
5 lbs would be very interesting.
Atmospheric pressure is 14 psi ( approx ) so at 5 it had become a vacuum pump, or we have entered the " Twilight Zone " ( cue creepy music )
 
bertsmobile1 said:
5 lbs would be very interesting.
Atmospheric pressure is 14 psi ( approx ) so at 5 it had become a vacuum pump, or we have entered the " Twilight Zone " ( cue creepy music )
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It was a joke Bert. I meant the old motors are hard to kill. Kill meaning stop running. Stop meaning zero revolutions per minute.

slomo
 
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