Murray engine troubles

[handirifle]

I just bought (yesterday) a Murray riding mower from a private party. The guy said he had just spent $200 on maint items, plugs, new battery even new brakes on it.

I tested it and everything worked fine. Engine had a little pop every now and then, but so does my Husqy push mower, so no biggie. Plenty of power etc. So I bought it. Took it home and got about 75% of my 3 acres mowed, when it started backfiring, and wouldn't fun below half throttle.

It's a 20hp Briggs n Stratton, engine mod 460 777 type 1877 A1, and I already did some research on it. It is the opposed cyl engine, not a v-twin. Pulled flywheel nut to look at keyway, it looks perfect. Then I did a compression test. The cyl on right (passenger) side has about 100lbs, but the left side has ZERO.

What's the most likely culprit here? I didn't hear anything sounding like it broke, and nothing rattles.

What's a rebuild likely to cost?

 

[SandburRanch]

I just bought (yesterday) a Murray riding mower from a private party. The guy said he had just spent $200 on maint items, plugs, new battery even new brakes on it.

I tested it and everything worked fine. Engine had a little pop every now and then, but so does my Husqy push mower, so no biggie. Plenty of power etc. So I bought it. Took it home and got about 75% of my 3 acres mowed, when it started backfiring, and wouldn't fun below half throttle.

It's a 20hp Briggs n Stratton, engine mod 460 777 type 1877 A1, and I already did some research on it. It is the opposed cyl engine, not a v-twin. Pulled flywheel nut to look at keyway, it looks perfect. Then I did a compression test. The cyl on right (passenger) side has about 100lbs, but the left side has ZERO.

What's the most likely culprit here? I didn't hear anything sounding like it broke, and nothing rattles.

What's a rebuild likely to cost?

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QUOTE:
"What's the most likely culprit here"? One of the valves on that non compression cylinder is stuck open.

 

[handirifle]

Well, you're partly right. After posting I went to a local mower shop and spoke to a guy there, and he told mea bout a possible stuck valve. I purchased some penetrating oil to use to "unstick" it. So I went home, pulled the head, and both valves were closed. Hmmmm

I pulled the other plug, and rotated the crank to watch function. Seemed normal, so I thought I'd spray someup towards the guides, just in case one had a tendacy to stick and this would help.

That's when I discovered the REAL problem. When I stuck the spray tube into the valve area, a little ring fell onto it. As I looked it over, I realized it was the valve seat, for the exhaust valve. Another call to the repair shop, the guy tells me I should be able to just put the seat back in place and peen the cylinder around it and it would stay in place.

Well back to the engine and the darn seat doesn't seem to want to stay in place. Looking a little closer, I see a shiny area at about the 7 o clock position around the seat. A closer look at this area and I see an egg shaped area that can't be good.

So I pulled the other head off to compare, and it was what I feared. The valve seat has beat the crap out of the area it's supposed to stay in. Being a flat head engine, this cylinder is shot.

Anyone know what my options are? Can I get a replacement cylinder? A new engine is at least $550, and that is a lot more than I can spend right now. I paid $500 for this thing two days ago and it looks like I'm going to spend quite a bit more to fix this.

 

[SandburRanch]

Possibly a mouse nest under the shroud caused too much heat. Maybe it's time to see just how good JB weld is. Clean it good, apply enough to fill the egg cavity, place the seat in the hole and then install the valve so it centers the seat concentric with the valve. Not much to loose but time. I know a fellow that filled a grooved piston with JB and it ran a long time.

I suspect many miles separate us but I have an opposed twin engine in a craftsman you could have.

 

[handirifle]

Possibly a mouse nest under the shroud caused too much heat. Maybe it's time to see just how good JB weld is. Clean it good, apply enough to fill the egg cavity, place the seat in the hole and then install the valve so it centers the seat concentric with the valve. Not much to loose but time. I know a fellow that filled a grooved piston with JB and it ran a long time.

I suspect many miles separate us but I have an opposed twin engine in a craftsman you could have.

Well when I pulled the shrouds off there was a ton of crap in there. I blew that all out, first thing. I knew it wasn't doing the engine any good. Looks like it did it worse than I suspected.

Depending on what my options turn out like I just might try the JB. The big problem, is, it looks like the valve seat chewed up the entire exhaust chamber and there may not be enough to weld it to. It's a real pisser.

By the way, I live in central coast of CA. Is yours a 20hp?

 

[mark1]

Join the club..I bought a Murray rider years ago.2 cylinder B&S 16 or 18 Hp (I forgott which) the guy said it ran like a top and it did sound good.after paying good money, and using it for about 45 minets it started backfireing I also had "0" compression in one cylinder and found the valve seat had been beaten to death.the valve and seat are part of the crankcase not a replaceable head. I took it all apart and went to a local machine shop. they wanted a ARM and a LEG to clean up the hole and insert an new seat and then would not gurantee it would last. I took it all back gave everything to the local scrap guy for metal scrap.(you ain't the only one who gets screwed!). If you like the mower get a replacement engine. If not cut your losses and dump the whole thing!( he probably Jurry rigged other things on the mower tooooo)

 

[handirifle]

Well I talked to a repair guy and he told be basically what you just did. I knew the valves were in the cylinder, but figured the cylinder was replacable. NOPE. He said the cylinder is part of the block assembly.

I have found listings of replacement engines for this model, out of stock, but they list at over $1500????? All this for a $500 mower!!!

 

[handirifle]

Join the club..I bought a Murray rider years ago.2 cylinder B&S 16 or 18 Hp (I forgott which) the guy said it ran like a top and it did sound good.after paying good money, and using it for about 45 minets it started backfireing I also had "0" compression in one cylinder and found the valve seat had been beaten to death.the valve and seat are part of the crankcase not a replaceable head. I took it all apart and went to a local machine shop. they wanted a ARM and a LEG to clean up the hole and insert an new seat and then would not gurantee it would last. I took it all back gave everything to the local scrap guy for metal scrap.(you ain't the only one who gets screwed!). If you like the mower get a replacement engine. If not cut your losses and dump the whole thing!( he probably Jurry rigged other things on the mower tooooo)

How much was the ARM and LEG exactly?

 

[SandburRanch]

How much was the ARM and LEG exactly?

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That information is posted on nearly every gas pump.:laughing::laughing:

 

[handirifle]

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That information is posted on nearly every gas pump.:laughing::laughing:

Huh????