CK35 HST shattered piston at 400 hours

[holeycow]

I'm well aware of how engines work; especially after having owned and run a foreign auto repair shop for over ten years. We rebuilt all kinds of engines, including Mercedes Benz diesels, as well as Volvos, Saabs, and all kind of eccentric, and unusual autos from all over the world; Lambos, Maseratis, Jags, Talbots, Rolls Royce, to name a few.

The additional pics, (I did not look at them beyond noting they were available to look at), may indicate serious to severe damage from the piston debris getting 'hammered' by the still running engine; yet another reason to NOT restart the engine again.

And yet another reason to just get a new motor. The Kioti engineers need to have a look at that one. They need to get to the bottom of this ASAP.

 

[Fawken]

And yet another reason to just get a new motor. The Kioti engineers need to have a look at that one. They need to get to the bottom of this ASAP.

I don't think it was the result of any inherent design or material flaw. More likely a 1 in 10,000 assembly issue. Pistons are checked and re-checked before assembly. This one could have been dropped or simply put into the cylinder improperly. Hairline cracks are hard to see but on aluminum they just get bigger. They could use it as a reminder for the assembly line. Daedong makes quality diesels for all kinds of machinery.

 

[holeycow]

I agree.

 

[Coyote machine]

This is ONE piston out of thousands that Daedong puts into equipment markets all over the world. This tractor can't just have a new engine ordered up and replaced. There are many factors coming into play, not the least of which is Kioti Corporate's decisions regarding the repair of this motor. And the selling dealer's participation, as well as the OP's.

It's also possible Kioti could decide to take over this situation and do a non-disclosure settlement, and keep the entire outcome in house.
This is entirely within the realm of choices. For instance, when I dealt with Kioti regarding the DK series squeal in reverse, I was granted certain access that I had to agree to beforehand to not release to anyone, and not to post any drawings on TBN or elsewhere, from the discussions I had with Kioti's internal engineering technicians.

The outcome will be determined by those parties, so everybody should sit back and wait for the OP to give us further details, as they become available to him; earliest is likely beginning of next week.

 

[MinnesotaEric]

A motor will run just fine without a wrist pin retainer, but eventually the wrist pin will migrate to the cylinder wall and over time wear a groove in the bore to where you will notice a significant amount of bluish smoke in the emission. That retainer popped out when the skirt finally gave way as the bottom part of the groove is located in the shattered portion of the skirt. A lot more is clear with the additional pictures he posted. Some small fragments appear to have been floating in and around the crankshaft long enough to show buffing and grinding at work. A tough rebuild for sure.

On racing engines I've had wrist pins snap in half and the engine still ran and made power (along with a grenade-ing sound)

 

[MinnesotaEric]

It's pretty clear, Paul. Look at the picture on page five with the fragments on a paper towel. The large fragment at the top right shows 3 different levels of carbon deposit. The shiny area is where it finally gave way and came apart. Just above that is a medium area as the crack progressed. Then to right is a large dark area that was exposed to crank case vapors for a long time. It is possible to measure the amount a carbon deposited in that crack, compare it to the deposits in the the non contact area of the bore, and get a good estimation of when cracks first developed in that piston. Since it doesn't collide with anything in the crankcase with anywhere near the force required to shatter, it likely was installed with hairline fracture when assembled. He should get a new motor.

I took the liberty to annotate what you called our attention to.

That said, if there isn't anything on the oil pump pickup screen, and no scaring of the positive displacement oil pump gears, and the crank and connecting rods aren't too banged up and zero damage to any main bolts or connection rod bolts, and no damage to the crank, or valves in the head, I'd clean up the bore as needed, and pop in a piston with a new connecting rod, and wrist pin, and fire it up.

If the wrist pin scarred the cylinder bore, beyond a quick diamond hone, I'd look into the next over piston for just that cylinder.

On the other hand, maybe Kioti wants this engine for inspecting in which case, a short block sorts things out too.

We need to take this engine apart more to really know the extent of the damage.

 

[Fawken]

I took the liberty to annotate what you called our attention to.

That said, if there isn't anything on the oil pump pickup screen, and no scaring of the positive displacement oil pump gears, and the crank and connecting rods aren't too banged up and zero damage to any main bolts or connection rod bolts, and no damage to the crank, or valves in the head, I'd clean up the bore as needed, and pop in a piston with a new connecting rod, and wrist pin, and fire it up.

If the wrist pin scarred the cylinder bore, beyond a quick diamond hone, I'd look into the next over piston for just that cylinder.

On the other hand, maybe Kioti wants this engine for inspecting in which case, a short block sorts things out too.

We need to take this engine apart more to really know the extent of the damage.

Nice work, Eric! I need to learn to do things like that. Most of the time I'm looking at motorcycle innards to decipher what went wrong. My dad was an engineer for NASA and Rockwell. I used to get so impatient with him when we worked together in an electronics repair business I owned in the 80s. I would find an obviously burned out resistor or cap, replace it and say, "Look Dad how quickly I got this camcorder fixed!" He'd reply, "You fixed nothing. Now you've only made it more difficult to diagnose why those components failed." He was meticulous to a fault. The same applies here and my theories on what might have caused this extremely unusual failure are jut that- theories. The different levels of soot deposition, however are definitive proof that this was not a sudden-impact failure, but happened over time.

 

[Fawken]

Also, I am not sure you can oversize just one cylinder. That is a no-no with the multi-cylinder bikes I work on. It supposedly induces vibration, but the bikes are revving at upwards of 14k RPM.

 

[MinnesotaEric]

Also, I am not sure you can oversize just one cylinder. That is a no-no with the multi-cylinder bikes I work on. It supposedly induces vibration, but the bikes are revving at upwards of 14k RPM.

I bet the bore isn't scarred beyond a quick diamond hone.

Anyway, its late and I wasn't thinking: the next over piston weight would need to be in the spec range to get away with it or primary balance of the engine would be off.

 

[CenTex Chris]

There are many factors coming into play, not the least of which is Kioti Corporate's decisions regarding the repair of this motor. And the selling dealer's participation, as well as the OP's.

Indeed, the exact words I received from Kioti customer service via email on Friday: "There are many variables to consider."

The selling dealer just wants to replace the broken #2 piston. They don't want to touch the other two. Not sure how comfortable I am with that.

I'm not expecting Kioti to replace the short block. I'm not expecting anything from them, actually. We'll just have to see what happens.

I have another lengthy reply or two in work that answers some other questions that were brought up a page or two ago. I'll have that posted tomorrow.

Meanwhile, thanks all very much for your continued interest and suggestions.