My experience with gas engines is that once they are honed, that they need to be cleaned with dishwashing detergent to get the fines out of the microscopic scratches that the honing creates. If you don't do this, then the rings will wear out prematurely. This is usually done in the machine shops that have the equipment to wash an engine block in a large machine. The dishwashing method is for those that do it in their backyard. This was shown to me many decades ago by a person that did engine rebuilding. He took a brake cylinder for his example and honed it. Then he flushed it with brake cleaner and wiped it out with a cloth. Then he handed me a clean white cloth, and put some oil on it, and told me to wipe it inside the cylinder. It came out with grey matter on it, which were the fines from the honing. Said the same thing happens with engine blocks.
Piston Metal on Cylinder Wall
- Thread starter wdlanning
- Start date
The block is a type of cast iron.
The pistons are aluminum.
What you are seeing is what I call metal transfer. This happens when the engine is overheated. Why? Aluminum's thermal expansion rate is much higher than cast iron; IOW, aluminum will expand a LOT more than iron does. So when you start a cold engine, the engine warms up with usage....the bores are considerably larger than the pistons when cold; when at operating temp those clearances close up by design, and the engine becomes much more efficient. But-if the engine is allowed to overheat, the aluminum pistons keep expanding until the clearance between the pistons and cylinders completely close up, it keeps expanding (or trying to) until there is metal-to-metal contact. That causes excess friction and heat, a runaway cycle, which melts parts of the pistons to the cylinder wall (which is what you are seeing). Also, as this is happening the cylinder walls are also worn off by the piston rings among other things, so normally when overheated to this extent the bores are oblong, they are tapered, they are junk-requiring a bore and hone to correct them. Failure to bore/hone after a seizure will result in a second overhaul; IF it ever has enough compression to start/run after the first one.
I've seen this a bunch of times. I have even done it on my own equipment.
The pistons are aluminum.
What you are seeing is what I call metal transfer. This happens when the engine is overheated. Why? Aluminum's thermal expansion rate is much higher than cast iron; IOW, aluminum will expand a LOT more than iron does. So when you start a cold engine, the engine warms up with usage....the bores are considerably larger than the pistons when cold; when at operating temp those clearances close up by design, and the engine becomes much more efficient. But-if the engine is allowed to overheat, the aluminum pistons keep expanding until the clearance between the pistons and cylinders completely close up, it keeps expanding (or trying to) until there is metal-to-metal contact. That causes excess friction and heat, a runaway cycle, which melts parts of the pistons to the cylinder wall (which is what you are seeing). Also, as this is happening the cylinder walls are also worn off by the piston rings among other things, so normally when overheated to this extent the bores are oblong, they are tapered, they are junk-requiring a bore and hone to correct them. Failure to bore/hone after a seizure will result in a second overhaul; IF it ever has enough compression to start/run after the first one.
I've seen this a bunch of times. I have even done it on my own equipment.
i pushed the number 2and 3 piston out had my mentor over to measure the piston bore on all 3 he said that the wear is minimal . i was glad for that until i grabbed the pto shaft in front to see the crankshaft turn and could feel something slow down the turning i mentioned to my partner this could be bad . i crawled under the engine and could see at back part of crank that a bearing going into back of the block had been rubbing on the counter weights and heating the castiron up a bit. so i think it is time to pull the engine and see is going on with this motor. when you are going down the rabbit hole is this like being chased by wolves? just saying
Pau7220
Well-known member
Equipment
L3650 GST, Landpride TL250 FEL w/ Piranha, 6' King Kutter, GM1084R Finish
Lugbolt... I think this post got really screwed up. I believe the overheated China syndrome engine was in February/ March 2021. Then yesterday pa-sf started his washer in the cylinder problem on this post.
Somebody correct me if I'm wrong..........
you are right about my engine with the washer in the number one piston ,good eye. so now after pushing all three pistons out and doing a snap gauge test which come out with very taper i discovered the crankshaft counter weight has been brushing the lower thrust bearing this is bigger problem than i thought. i will be pulling the engine soon to see what the heck is going on with the b-6200.
Pau7220
Well-known member
Equipment
L3650 GST, Landpride TL250 FEL w/ Piranha, 6' King Kutter, GM1084R Finish