Briggs and Stratton 18.5 OHV locked up

jimkerr12 said:

Well... Flywheel key replaced, however, I was wrong about the piston moving up and down. Still only moves to the top then stops untill i push it back in. flywheel spins forever, valves are both doing their work... sounds like I may be screwed huh? Any Idea why this is happeniing?

Thanks for all your help so far :smile:

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:frown: Push it back in? Uh, oh. That means the rod is pooched. The valves are working because the rods doesn't effect their operation. Sounds like the crank throw catches what's left of the rod and pushes the piston up but when the throw (crank pin journal) goes down to complete the revolution theres nothing to pull down on.

Sound like its time to pull the engine apart for a look see.

An online over-haul:licking::thumbsup: Are you up for an over haul?

HI
SOUNDS LIKE MAYBE LOW OIL & THE VALVE SEIZED OPEN STOPPING THE PISTON. SAID YOU HAVE HEAD OFF, WHAT ARE THE VALVES DOING? YES CAPS LOCKS - I CAN SEE WHAT I TYPE, KINDA:laughing:
STEVES

missed post of flywheel, yes sounds like crankshaft/rod issue! time to tear down.
this capslock thing!
STEVES:confused2:

Sounds like wristpin fell out. Rods in cylinder pushing piston up and thats why piston stays up probably messed up bottom of cylinder also.

So jimkerr12, what were the results of your engine seized issue? I am having a very similar situation.

Hello,

I'm having same issue and have my entire engine in pieces. I will post the pics of where I think the problem is a and the parts affected. I definitely see wear on the cylinder and metal chips fraying away on the inside. My questions is going to be: Why did this happen? What parts are still salvageable and which ones do I need to replace? How to fix this problem?

All answers will probably come easier once you see my photos. I'm referring to same engine, I believe.

jasonchiefoil said:

My questions is going to be: Why did this happen?

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The list of why can be a bit of a puzzle, but here's some ideas,


- low oil
- oil not serviced properly (viscosity breakdown)
- metal fatigue ( wrist pin is steel and con rod is Aluminum. Eventually wear is going to occur no matter how well it is serviced)
- Heavy use
- A ring break (jam the piston in the sleeve)
- Sudden stop on crank and flywheel key doesn't break way
- Break-away key replaced with a piece of steel key stock

I'm guessing here of course, but as easy as these little engines seem to be, sometimes figuring them out takes some time.

I had a little 3 1/2 hp engine one my bench one time that met specs, everything went together the way it should have, but it wouldn't fire.

Would just fart every now and then.

Long story short the keyway on the crankshaft was worn so the there was some slap when the flywheel was turning. Threw the timing out. We changed out the crank and vroom.

The crank is harder than the flywheel key so what would cause the wear? Flywheel nut slack off a bit and the flywheel wobbled? Rough use?......Will never know I guess. Sometimes I think it's best to learn thinking outside the box......lol.

Course that will never happen again..............lol