Quick Rod Bearing Question

[SHO#7]

I am in the middle of doing a rod bearing replacement and the bottom one looks fine, however the top has about a dime size spot of copper. ( Guess that was just in time. ) And my question is this, the backs of the bearing look like they have some copper scratches and look overall pretty sad. Is this normal, or was I very close to a spun bearing. The motor is very clean. I have never seen one cleaner. I did not hear any noises either.

Just kinda wonder if there is anything else that I should look for. I am going to let her drip tonight. And do the rest and re-assemble in the morning. I have only done one so far. Just could not wait to look and see what they looked like.

This is on a 93 MTX with approx 129k.

 

[Off Road SHO]

A dime sized spot of copper on the top ones is not bad at all. The top ones get most of the hammering from the explosions, the bottoms ones only get a little pounding when you use the engine to slow down. The ugly stuff on the backside of the bearings is just chemical wicking in between the rod and the bearing; remember, those two parts are mated together with no movement (and therefore no oil either) between them. Because they are two dissimilar metals, they are susceptable to galvanic action, AKA corrosion. Even though one is lead compound coated with lead being a very inert metal, you still get some corrosion.

Good luck, and don't forget to use assembly ****, white lithium grease or STP oil treatment on the rubbing surfaces.

Tom

 

[revhardSHO]

A dime sized spot of copper on the top ones is not bad at all. The top ones get most of the hammering from the explosions, the bottoms ones only get a little pounding when you use the engine to slow down. The ugly stuff on the backside of the bearings is just chemical wicking in between the rod and the bearing; remember, those two parts are mated together with no movement (and therefore no oil either) between them. Because they are two dissimilar metals, they are susceptable to galvanic action, AKA corrosion. Even though one is lead compound coated with lead being a very inert metal, you still get some corrosion.

Good luck, and don't forget to use assembly ****, white lithium grease or STP oil treatment on the rubbing surfaces.

Tom

What do you think about using a bit of oil on the backside to prevent corrosion? Or is that a ?

 

[yamahaSHO]

I use a VERY LITTLE amount of assembly **** on the backside. You really don't want or need a whole lot. You don't want that part slipping. Although, when your motor runs, oil gets in between the rod and bearing.

 

[Off Road SHO]

If you're going to try and seal out the corrosive chemicals, I would put an extremely thin layer of oil. You don't want anything taking up space temporarily while you are torquing down the rod bolts. You'll get the required torque but eventually that oil layer squeezes out the sides and you're left with a gap. Like Jason says, a small amount. You could wipe it on with an oily rag and you would have enough on there.

Remember the lead compound acts as an anti corrosion layer also.

Tom

 

[SHO#7]

FINISHED. Thanks to YamahaSHO and Off Road SHO for the advice. It was not really a hard job, and I encourage people not to be scared of doing it. The only thing to look out for is the snapping of all four exhaust studs like I did. Granted though, I work in a shop and have access to just about every make easy tool that is made. So flame and a stud extractor, made it a quick fix.

I can now rev her freely and have no worries for another 129k miles

 

[autobahnsho]

FINISHED. Thanks to YamahaSHO and Off Road SHO for the advice. It was not really a hard job, and I encourage people not to be scared of doing it. The only thing to look out for is the snapping of all four exhaust studs like I did. Granted though, I work in a shop and have access to just about every make easy tool that is made. So flame and a stud extractor, made it a quick fix.

I can now rev her freely and have no worries for another 129k miles

I'm jealous.

Congratulations, though.