B&S Fail

[AVIVIII]

My father has a nice, 2 year old Husqvarna 23hp garden tractor with a 48" deck that has seen only regular to light service since he has owned it (~90hrs) mowing 2 acres of lawn.

Last week, he leaned down to pick up a dog toy from the yard and the "safety switch" on the seat cut the tractor off momentarily. Usually, the tractor keeps running, reset the PTO and you're on your way. Not so much this time. When he put his weight back on the seat, the tractor backfired and ran extremely rough; one cylinder rough... He limped it to the garage, pulled the plugs, cleaned them, quick compression check with his thumb and put it back together. Still, no dice. So he put it on the trailer and took it to a small-engine shop down the street. The guy looked at it, pulled the valve cover off and said,

"Where's your other pushrod?"

WHAT?? I kid you not, one of the push rods was completely missing. The remaining one was bent. We figured out from the remaining one that the pushrods are aluminum with steel ends. We drained the oil; no sign of pieces of push rods. We cut open the oil filter, still nothing..... Further inspection (and a brighter light) showed something out of place in the bottom of the head. All you could see was a little nub poking out through a hole. I got a pair of long needle nose pliers, but we couldn't budge it. I thought I had it for a sec, but just ended up pushing it further in....

Sooo, we pulled the engine, split the case, and this is what we found:

We are about to order new parts and they offer both a steel and an aluminum option for the replacement push rods. The saving grace for the engine was that the aluminum had ZERO affect on the hardened gears inside. The flip-side is, steel probably wouldn't have bent on the first place....

What do you all think?

 

[andres14725]

It would be interesting to see whether the piston contacted the valves. Are there any marks on the piston crown? Are the valves still OK? You may want to check that the valve heads are still square to the stems. I assume the rockers survived?

 

[AVIVIII]

The rockers are fine and the valves still move fine, so we were assuming that they are fine. We borescoped the piston and no marking. We are really trying to avoid pulling the head....

 

[crazyal]

I rewired my rider. The cheaper mowers just use a lever to tighten up a belt while the nicer ones have an eltromagnetic pto with a switch to engage it. I removed the wires that kill the engine and now it just disconnects power to the pto.

I seamed like when I was much younger riders came in two models, the cheap 8hp model and a nice 12hp model. The cheap ones were usually $999. The nicer models ranged up to $2000. Now you can't even find a 8hp riding mower. Now for $999 you can get a 18hp engine. I have to believe they must have done something to be able to sell a rider with more than twice the HP for the same price 30 (or so) years later.

At least it looks like you'll get out of this for not too much money.

 

[AVIVIII]

The seat safeties have all long since been disabled on my tractors, the Husqy will be following suit.

I'm not very old, but it seemed when I was younger, HP actually meant something and was actually relative to the power of the engine. Not that the Husqys not a good tractor, but my 1968 12hp Cub Cadet could pull that "23hp" tin thing up a cliff-side without coughing...

I was showing a friend my John Deere 430 mower and his response was "Pfffft, its only 20hp?"

We ordered the aluminum pushrods and a couple spare gasket sets incase this happens again....

 

[Fixemall]

Check for recalls on that thing, it seems to me that a lot of those things got out of the factory with a little bit too much timing advance. Might be a good time to correct the problem.

 

[jonyyuma]

My seat switch quit working on my old deere mower. i don't miss it cutting out the engine? What a photo of the pushrod, beats anything lately around here?

 

[LBrown59]

I was showing a friend my John Deere 430 mower and his response was "Pfffft, its only 20hp?"

..

How much does he think it needs.

 

[AVIVIII]

How much does he think it needs.

Well, he just bought some Craftsman piece of tin that had a 26 hp engine in it.

I reminded him of a few more specs:

Weight: His- 700lbs My 430- 1500lbs
Deck width: His- 48" My 430- 60"

and the fact that his back tires are only 20"; my front tires are 18"... I tried to explain what torque was, but he just wasn't having it...

 

[tcartwri]

I've had to do the same thing to retreive a broken pushrod. It is a known issue with these motors and you will likely have to do it again. So my advice is to shut the motor off the next time it starts missing and pull the pushrods out before they migrate into the crankcase. The steel ones will bend by the way.

In my case it was the valves sticking in the valve guides. In other peoples experiences it was the guides migrating out of the head and interfering with the valve spring retainer. Both will cause the pushrods to bend or snap. The only fix is to replace the head as an assembly or it will keep happening.

The only preventative thing you can do is to keep your fins and fan free of debris, so that the motor doesn't overheat and obviously avoid backfires as much as possible.

These are non interfering motors, so there is no way for the valves to hit the pistons, even if they are stuck wide open.