YZ125 Crank Replacement?

OneDirtyMXRider
Edited Date/Time 1/24/2012 2:38am
What do you think happened here?

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lumpy790
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lumpy790 12/18/2011 9:50pm
12/18/2011 9:50pm
looks stock? Is there any up & down play? Is the side thrust washer clearance within spec?
jsmx97
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jsmx97 12/29/2011 8:04pm
12/29/2011 8:04pm
If there is no up and down play and the rod side to side clearance is under 28 thou, dont worry about it. The blue is from the crank assembler heating the flywheels to ease the installation of the crank pin. I have gotten many many brand new crank shafts with blueing like that.

looking though the rod it looks as if the bearing looks good, but again always measure clearances!!
TerryK
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TerryK 12/30/2011 10:31am
12/30/2011 10:31am Edited Date/Time 12/30/2011 10:32am
jsmx97 wrote:
If there is no up and down play and the rod side to side clearance is under 28 thou, dont worry about it. The blue is...
If there is no up and down play and the rod side to side clearance is under 28 thou, dont worry about it. The blue is from the crank assembler heating the flywheels to ease the installation of the crank pin. I have gotten many many brand new crank shafts with blueing like that.

looking though the rod it looks as if the bearing looks good, but again always measure clearances!!
Ummm....if the guy that assembled that crank heated it to the point of bluing he needs to be flogged to within an inch of his life. That thing has been waaay over heated.
easton
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easton 12/31/2011 4:04pm
12/31/2011 4:04pm
If you can twist the crank pull it. The color looks to me as if my neighbors kid try to install the crank. Was it ballanced, why so much heat. With that much heat the shell just lost it's true round and the bearings will fail soon. Remember after you heat something that much it shrinks.

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tmauto769 12/31/2011 5:48pm
12/31/2011 5:48pm
jsmx97 wrote:
If there is no up and down play and the rod side to side clearance is under 28 thou, dont worry about it. The blue is...
If there is no up and down play and the rod side to side clearance is under 28 thou, dont worry about it. The blue is from the crank assembler heating the flywheels to ease the installation of the crank pin. I have gotten many many brand new crank shafts with blueing like that.

looking though the rod it looks as if the bearing looks good, but again always measure clearances!!
I have bought new cranks that have that bluing as well, and actually a lot worse than that. Quite a few actually, I just thought that was normal????
MOTODAD422
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MOTODAD422 12/31/2011 6:40pm
12/31/2011 6:40pm Edited Date/Time 12/31/2011 6:43pm
jsmx97 wrote:
If there is no up and down play and the rod side to side clearance is under 28 thou, dont worry about it. The blue is...
If there is no up and down play and the rod side to side clearance is under 28 thou, dont worry about it. The blue is from the crank assembler heating the flywheels to ease the installation of the crank pin. I have gotten many many brand new crank shafts with blueing like that.

looking though the rod it looks as if the bearing looks good, but again always measure clearances!!
TerryK wrote:
Ummm....if the guy that assembled that crank heated it to the point of bluing he needs to be flogged to within an inch of his life...
Ummm....if the guy that assembled that crank heated it to the point of bluing he needs to be flogged to within an inch of his life. That thing has been waaay over heated.
I bought 7 RM85's from 05 to 09 and every one of them had discoloration there. The first one i was replacing the first piston in it and i thought there was something wrong with the crank and or lower rod bearing.Then someone at the the track told me that they heat them to ease assembly from the factory.Then when i got another new one i took it apart before running it and it was the same way. But that YZ looks a lot more discolored,i would be suspect.
jsmx97
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jsmx97 1/2/2012 7:40pm
1/2/2012 7:40pm
jsmx97 wrote:
If there is no up and down play and the rod side to side clearance is under 28 thou, dont worry about it. The blue is...
If there is no up and down play and the rod side to side clearance is under 28 thou, dont worry about it. The blue is from the crank assembler heating the flywheels to ease the installation of the crank pin. I have gotten many many brand new crank shafts with blueing like that.

looking though the rod it looks as if the bearing looks good, but again always measure clearances!!
TerryK wrote:
Ummm....if the guy that assembled that crank heated it to the point of bluing he needs to be flogged to within an inch of his life...
Ummm....if the guy that assembled that crank heated it to the point of bluing he needs to be flogged to within an inch of his life. That thing has been waaay over heated.
Your statement is purely incorrect...I am not trying to be rude, but I dont know how else to put it. Talk to some veteran powersports machinist in your area if you really didn't know that bluing on the crankshaft flywheels is normal in some cases. Again I am not trying to offend you are be rude, but I think you are misinformed.

Yes it is possible for bluing to appear after a rod bearing failure, but having that coloring on the crankshaft does not indicate a bad crank or that it was OVERheated during crank pin install.

Just got 2001 and 2008 crankshafts in today from hotrods, and both have bluing near crank pin. I guess it is possible the assembler at hotrods is incorrectly heating the flywheels when installing crankpins on these cranks along with the 50+ other cranks I have gotten with that same bluing, but to my knowledge the ones that did I have never had any premature failures or issues.
sec114
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sec114 1/2/2012 7:51pm
1/2/2012 7:51pm Edited Date/Time 1/2/2012 7:53pm
i guess it can be confusing since we are not told of even why the question was asked. such as, was there a crank failure, funny noise or vibration etc..... and that is why you are asking about the bluing. or you just take cylinder off to re-ring, and happen to notice the bluing and just wondering for the curiosity of it? or in other words, he is asking us what happened here and not telling us what happened to get to this point. more information would be helpful.

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