18 hp briggs

[bill mart]

Working on a 1992 Craftsman rider with a Briggs twin cylinder 18 hp verticle shaft engine. Seems to have a knock to it, maybe in the upper half. Are these engines known to go bad? The reason I ask is the deceased owner had an extra 18 hp engine laying in pieces behind the shed the mower was in. Bill
 

[JT]

The biggest "common" issue with these engines were valves. Seats falling out and guides getting loose. A knock can also have carbon buildup in head and piston hitting it. Easiest thing to do is pull heads and take a peek at top end of engine. You can check seats, guides and cylinder for wear or piston slap.
 

[rrobert]

And check for compression.

I had an 18 hp that the valves would stick when it got warm.

I had a 16 Hp Vortec that ran but seemed flat like the governor was missing. It ended up being that one connecting rod was broken.
 

[bill mart]

thanks to all,will probably pull the heads,will check compression before and after. Bill
 

[wisbaker]

Some of that newer B&S stuff says "use synthetic oil only" I hear if you don't you get valve problems.
 

[JT]

I am a Briggs Master Tech and have not seen Briggs telling you to use synthetic oil. As for valve problem issye in newer OHV Briggs engines, if you use gas that gets a little old and stale, it will cause valve stems to get deposits on them, stick in guides, and push guides out of heads and bend push rods.
 

[d beatty]

I have a Briggs 18 HP opposed two cylinder.If I let it set over winter it wants to knock for a while but comes out of it. If I start it ever several weeks it wont knock. I can now let it set over winter sinse I use Lucas oil treatment. If it sets for a long time oil drain away from top bearing.
 

[Bill Hazelbakerxads]

Replaced mine 2 times before we found out it was carbon build up on top of pistons. Went to straight 30 weight oil and no problem for several years now