Let's Play Diagnose My Toasted GTX 951 engine!

[SoloZ06]

The engine is an 11 year old SBT engine. There was plenty of oil on all parts and no evidence of water ingestion. The piston with the broken ring is from the PTO side. I'm not sure if you can see in the picture, but the ring locator pin for the missing ring is gone. There was quite a bit of sand in the water jackets.

Here are the pictures:


I'm wondering that with a well worn engine and a potentially hot engine, the top ring snagged on a port. Based on the location of the missing piston chunk, the lack of damage to the power valves, and a small nick on the edge of a transfer port i'm guessing it wasn't the exhaust port even though that's what I would expect to happen. What do you all think?

 

[Matt Braley]

It detonated. You have done good to get 11 years out of it but now the pto side has run lean on fuel. If your fuel selector is functioning properly then your carb needs a rebuild. If not then it could be the filter/water collector full of trash or leaking air in. If an engine seal failed(like the pto side crank seal) then that will suck air in and cause the engine to run lean also.

 

[Dr Honda]

RUST !!!!!!!



See all the speckles on the cyl wall, and piston skirt??? That was poor winterization. So... you pulled and cracked the ring on the busted up piston. But before the ring broke, you killed the edge of the ring... and there was blow-by. (you can see the dark, cooked oil just under the ring.

Because of that... don't try to just rebuilt the top. There's a good chance that the bearings in the lower are pitted.

So there you go.

 

[SoloZ06]

Thanks Matt and Dr. Honda. I just picked this up not running, but based on its condition when I first got it, I would guess that there was not much, if any maintenance going on. I'll be putting in a new crank and top end and will be going through the entire fuel system.