Model 28 Vertical - No Compression

[Humbug]

Hi All,

I was using my Etesia Bahia Mower today when there was a loud bang from the engine (I think, I had my ear defenders on) and it quit running. I tried the starter but it sounded like there was no ignition and the engine was turning over much more easily than normal. I pulled the spark plug and screwed in my compression tester, when I turned it over the compression was zero.

The engine is a B&S 28M707-1187-E1, vertical 4 stroke, 13HP Diamond I/C.

Could the complete lack of compression be caused by a blown head gasket or is it possibly something more serious? I can't see any oil leaking from it which makes me think that perhaps it isn't the gasket but I'm a bit of a novice when it comes to engine repair. That said, I'm not afraid to get stuck in and get my hands dirty.

Thanks in advance for any advice,
Paul.

 

[StarTech]

Could be as simple as the valve clearance have gone to zero with old L-head engine. Or worst a broken connecting rod. Remove the spark plug and check for piston movement.

 

[Bertrrr]

Stick a small rod in the spark plug hole and roll it slowly and make sure the piston is moving up and down , if you threw a rod it will not be moving and if that's the case you needn't worry about a rebuild , just replace the engine or mower itself

 

[Humbug]

Thanks for the ideas guys. I tried putting a rod in the spark plug hole and turning the flywheel, there was no piston movement at all so I figured it was probably the con rod that had broke. I decided to pull the engine out of the mower to take a look, thankfully it was pretty easy to remove. I got it on the bench and removed the head. When I turned the flywheel the valves are both opening and closing as they should but the piston was stuck at the top of it's stroke. There was just enough of the piston exposed to gently grip it and pull it out of the cylinder. Sure enough the con rod had exploded at the big end and there was a lot of debris in there.

I looked for a replacement engine on Ebay and managed to find an identical one but it was $$$$. Given that I've got this far with it would it be fairly straightforward to replace the broken rod? If I go ahead with the repair I'm guessing that I'll need to replace the head and case gaskets, should I replace any others while I've got it stripped down? I guess I'll also need to remove the flywheel to open the case, any suggestions on how best to pull it?

 

[Tiger Small Engine]

Thanks for the ideas guys. I tried putting a rod in the spark plug hole and turning the flywheel, there was no piston movement at all so I figured it was probably the con rod that had broke. I decided to pull the engine out of the mower to take a look, thankfully it was pretty easy to remove. I got it on the bench and removed the head. When I turned the flywheel the valves are both opening and closing as they should but the piston was stuck at the top of it's stroke. There was just enough of the piston exposed to gently grip it and pull it out of the cylinder. Sure enough the con rod had exploded at the big end and there was a lot of debris in there.

I looked for a replacement engine on Ebay and managed to find an identical one but it was $$$$. Given that I've got this far with it would it be fairly straightforward to replace the broken rod? If I go ahead with the repair I'm guessing that I'll need to replace the head and case gaskets, should I replace any others while I've got it stripped down? I guess I'll also need to remove the flywheel to open the case, any suggestions on how best to pull it?

Did you run low on oil, or out?
Did engine overheat? Pull engine shroud and check top of engine and cooling fins for oil, dirt, and debris and remove as necessary.
What year and how many hours?

Once you open up the engine, you can determine what needs to be replaced. Check crankshaft for scoring and wrist pin. Check condition of piston, rings, and cylinder. Depending on hours and condition, it may just need a new connecting rod, gaskets, etc.

 

[Bertrrr]

Make sure your crankcase isn't damaged.
Valves maybe bent and head could be scored up too

 

[Humbug]

Did you run low on oil, or out?
Did engine overheat? Pull engine shroud and check top of engine and cooling fins for oil, dirt, and debris and remove as necessary.
What year and how many hours?

Once you open up the engine, you can determine what needs to be replaced. Check crankshaft for scoring and wrist pin. Check condition of piston, rings, and cylinder. Depending on hours and condition, it may just need a new connecting rod, gaskets, etc.

I think that the oil level was OK as I had only renewed it 3-4 months ago. I was mowing grass that was probably too long and wet . The mower bogged down a couple of times and I should have known to leave it but I thought I would just take about a third of a stripe at a time and all would be ok, clearly it wasn't!

I have the engine fully stripped down now and I have cleaned it up (although it wasn't too scruffy). Inside the case was a whole load of debris, it was like a box of grit! I cleaned it all up and and can see that there is some damage to the inside of the case but it isn't punched right through. Is the crank case under high pressure when the engine is running? Might I get away with it?

The cylinder looks really clean, as do the rings and piston but there is some scoring on the crank shaft, could that be carefully ground/polished out? The wrist pin is fine.

The mower is about 20 years old but it's in great condition generally. I think it was used commercially before I bought it - I hope that means it was well maintained. I've had it almost 5 years and it has been really solid.

 

[Humbug]

Make sure your crankcase isn't damaged.
Valves maybe bent and head could be scored up too

There is a little damage to the inside of the case but it isn't punched through. The valves appear to be OK. When I rotate the camshaft the valves appear to open and close smoothly. I cleaned the head up and it looks to be completely intact. Just some scoring to the crankshaft.

 

[Bertrrr]

Looks like you got lucky - a new rod might just be all you need along with gaskets etc.

 

[Humbug]

I’m making some progress with rebuilding my engine. I have ordered a gasket set and a new con rod. In the new gasket set there are 5 crankcase gaskets, 3 black, 1 brown and one light grey. Do I need to use them all? And if so, in what order should I stack them?