Bent con rod.

[Silk]

My 2nd week back at the Honda shop, and I've got an XR150 burning oil, I've been given a new barrel and piston, but it's had a new piston at another shop, so I need to keep my eyes open. This diagonal wear pattern on the piston means there is a bent rod, something we don't see much these days.




Splitting the cases I found a foreign body...there are marks in the crankcase mouth, probsbly caused by this. Caught between crankcase mouth and piston, it will have bent the rod.

 

[Jetronic]

so, did that get there when the piston was replaced, or wasn't found but caused the piston replacement?

 

[Cujet]

I don't see the wear pattern you are talking about. I do see a nice series of 3 machined grooves in the piston skirt. Maybe the picture is just not clear enough?

It should be easy to use a square to check the connecting rod.

Are you saying that nut was loose inside the crankcase? Yikes...

 

[crazyoildude]

Mileage/year?

 

[Silk]

I presume they just replaced the piston. It is very difficult to see the bent rod, I measured it off the studs, but a screwdriver between rod and flywheel each side was very obvious - the wedge goes in further on one side than the other.

 

[Silk]

Back together today - new rod and left main bearing, new piston and barrel, seals, gaskets etc. Runs sweet, no burning oil.

Yes, it is difficult to see the wear pattern on the piston, holding it in your hand you have to turn it around and check in different places...I think it's more obvious in the photo than in real life. I used to tell my apprentices, we are like detectives, always looking for clues, identifying them, acting on them. It's not about being the fastest guy in the shop...problem solving is what I get out of it.

 

[MolaKule]

Are you referring to the smooth wear pattern on the piston skirt?

It is still not clear as to what you are referring.

 

[Silk]

The wear pattern is diagonal, look at each corner of the skirt.