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2025/01/18 22:38:49

jamesdjones13076

Wierd hole in crankcase vent chamber

New guy here. I inhereted a old (1999) B&S L-head that I was told had run recently. Upon opening up the crankcase breather chamber, I found what looks like a poorly drilled hole (versus a neat hole in the casting) that I presume communicates with the crankcase. Two questions: (1) Do I assume correctly that there should be a hole in that chamber that drains oil back to the crankcase, and (2) any thoughts on why the condition/quality of the hole in the pic? I can't beleive it came from the factory like this. I plan on opening up the crankcase to see what the other side looks like. Many thanks for your input.

6 comments Leave a comment

SRTsFZ6

There's no pic posted and a full engine MODEL # would help.

The breather, on the older machines, used to vent to the atmosphere.
That hole allows the crankcase fumes (as positive and negative pulses
happen due to the piston going up and down) to vent.

Again, in the older machines, the valve spring access cover used to have
a "spongy type" of material in it. That would catch most of the oil vapor and allow it
to drain back into the crankcase (thru a smallish hole). Some machines, the spongy material just sat inside that
area.

Newer machines have a vent hose from the crankcase to the air filter area so the engine
can burn off the fumes and not release them into the atmosphere .

The engine parts diagram would show what should be installed in that area.

***Also, being a flat head engine, check, re-tighten the 3 HEAD BOLTS closest to the exhaust valve.
99% of the time they loosen up (hot and cold cycles) and need re-tightening. Very loose bolts
will keep the engine from running.***.

.

2025/01/19 06:55:45

jamesdjones13076

Thank you for the reply. Pic is now attached. This is a B&S model 257412. I'd like to verify that this issue isn't fatal to restoring the engine.

2025/01/19 11:12:11

SRTsFZ6

Part #8 is your cover with a mesh inside it:
https://www.jackssmallengines.com/jacks-parts-lookup/manufacturer/briggs-stratton/briggs-stratton-engine/200000-399999-series/257400-to-257499/257412-0115-e1/cam-crankcase-cover-sump-crankshaft-cylinder-head-valves-kits-gasket-sets-engine-kits-gasket-sets-valves-oil-piston

You can also see by the pic in the above link, that hole SHOULD BE THERE.

I've never seen different valve retainers, etc, but apparently their are....

Button her up and enjoy..

.

2025/01/19 14:25:28

SRTsFZ6

Seems that hole should be there. In the parts diagram, it's drilled later, thus the angle:

2025/01/19 14:27:42

jamesdjones13076

I saw that too, Scott. A 1/2" drill bit fits perfectly in the hole, but doesn't go all the way to the other side. It just looks too rough to be manufactured that way, and there were fleks left over that I picked out with needlenose. I appreciate your reply.

2025/01/19 14:40:26

SRTsFZ6

Your very welcome.

Somebody may have opened it up some, but it should be there.

Good luck with the restore!

.

2025/01/19 18:08:08

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Wierd hole in crankcase vent chamber

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