Strange cylinder wear...

Had the cylinder bored to 101mm and a new Pro-X piston installed at 18340 miles.  Had to pull the head owing to a dropped valve seat at 24,500 miles and note this wear on the cylinder:

 

IMG_20140723_175446.jpg

 

IMG_20140723_175504.jpg

 

And a shot of the rear portion of the cylinder:

 

IMG_20140723_175454.jpg

 

The cross hatch is evident on the unworn portion, there was no damage to the valve/seat and running my finger nail across the "streak" does not reveal any surface imperfections, in other words, it is smooth.  There is some obvious wear areas in the front as well.  The work was done by a reputable machine shop.  Regular oil changes were performed up until head removal.

 

Last, but not least, the engine did not burn oil.  Do I need to worry about this?  Obviously a compression test should be performed but that is not possible now.  I have a spare piston with rings (new) for 102mm so I could re-bore but really do not want to with such low miles on the build....

 

Any input here???

So the worst wear is on the front of the cyclinder?????  away from the carb side?????

 

this is a counter rotating engine......the thrust side is the side towards the intake,wear that shows there and is slight,,is usually from dirt being brought in and crushed against the cylinder wall on the thrust side..and the force of compression pounds the piston against the thrust side,,,,eating the cylinder wall......sand ingestion will eat the piston and wall in short order.......

 

if you have wear on both sides......i`d be wondering if they followed Honda specs for piston=wall clearance.which is way too tight on a forged piston.......

 

oil starvation and overheating can cause this too..

 

So.second question,,is this a cast OE slug or forged?????????

 

either way,,not good,pull the cylinder and lets see the piston skirt.......if the harder cylinder wall looks like that,the piston is much worse..

 

 

 

B

Edited by brianhare

So the worst wear is on the front of the cyclinder?????  away from the carb side?????

 

this is a counter rotating engine......the thrust side is the side towards the intake,wear that shows there and is slight,,is usually from dirt being brought in and crushed against the cylinder wall on the thrust side..and the force of compression pounds the piston against the thrust side,,,,eating the cylinder wall......sand ingestion will eat the piston and wall in short order.......

 

if you have wear on both sides......i`d be wondering if they followed Honda specs for piston=wall clearance.which is way too tight on a forged piston.......

 

oil starvation and overheating can cause this too..

 

So.second question,,is this a cast OE slug or forged?????????

 

either way,,not good,pull the cylinder and lets see the piston skirt.......if the harder cylinder wall looks like that,the piston is much worse..

 

 

 

B

 

Worst wear is on front of cylinder, piston is cast (Pro-X)...

My guess...... is either too tight of clearance between piston and wall......a look at the skirt will tell more possibly.....the only other thing is a possibility it starved for oil/air locked pump or got extremely hot,,causing a mild seizure...

 

Any signs of rocker/cam wear or center journal wear from oil starvation???

 

B

My guess...... is either too tight of clearance between piston and wall......a look at the skirt will tell more possibly.....the only other thing is a possibility it starved for oil/air locked pump or got extremely hot,,causing a mild seizure...

 

Any signs of rocker/cam wear or center journal wear from oil starvation???

 

B

 

No rocker/cam wear, they all look great, save for what you would normally expect.  I am religious in checking the oil and it is always at or near the full mark, checked properly after running for 15-20 minutes.  I'm going to go with the possibility that the bore was not machined to proper tolerances as I suspect that is what happened here, leading to a mild seizure...

 

I guess I'll pull the jug and take a look at the piston, I'm not really looking forward to another rebuild but you have to do what you have to do...

If you install a forged slug go with arround 3 thou clearance on a JE........If using anything else use manu specs....do not use Honda specs unless it`s their piston..

 

B

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