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So I just replaced my crank bearings in my 99 cr125 and im going to either sell it or keep it. The one thing I worry about is that if I keep it a guy I know said I should have replace all the bearings in the motor. Is this true or will it be just fine how it is? And keep in mind that I have about 300$ more into it then what its worth.

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You always lose money rebuilding a bike then selling it... If it is still apart, you should replace all the bearings. If not I personally wouldn't worry about it. My crank was fried and so I replaced all my bearings along with a new crank. But in hind sight with the old bearings out and on my workbench they didn't need replacement. They turned smoothly with no resistance or noise.. Every bike is different of course but if it runs fine just run with what you got, or that's what I would do personally!

Good luck,

Chris

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I'm of a different opinion.. Since we are talking 2 stroke, and the crank bearings are separate from all the bearings in the transmission I think it's fine to just replace the crank bearings by themselves. Of course you should check the transmission bearings for wear/play the best you can while you have the cases split-I don't think they should automatically be replaced if they do not check bad.

 

On a 4 stroke where the engine oil is shared between the crank & trans I would always recommend replacing all bearings in the event of a catastrophic failure that put any amount of metal in the oil. If no metal in oil-I would check them and let them ride if they show no signs of wear or damage.

 

Keep in mind that sometimes attempting to remove a known good part in an attempt to put in a new part will often times result in big problems. What if you remove a perfectly good bearing and put a new one in at the wrong depth? You have just created a problem where none existed before. What if you damage the case trying to remove a blind bearing that showed no signs of wear? Now you are in it for a new/used case half and down time waiting on shipping.  I'm of the belief that you should keep it simple when you can do so. If you have to go back in later to replace a bearing that eventually wears out, so be it. By that time the engine will hopefully need a new top end anyway and it will be just a few extra steps.

 

I guess I've been lucky in that I have never experienced a non-crank related bearing failure in a motorcycle engine before. Lost lots of pistons, rod bearings, worn rings, bad shift forks, valve-train issues, worn dogs on the gears, etc; but never a failed bearing anywhere other than on the crank, or rod.

 

With that said, I recently rebuilt my 2 stroke engine and ordered a complete bearing set. While I was going through the rebuild I noticed that the factory bearings were of a higher quality than the ones in the kit. In short, I only changed the crank bearings, and left the rest of the transmission bearings alone as they were all perfect. I have a complete set of new bearings (minus crank bearings) sitting on the shelf for that day that one of them takes a dump.. I bet it will be a very long time before that happens.

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Nobody will believe you anyway if you replace all the bearings and will low ball you when you try to sell it.  My 81 YZ465 has only had the main bearings replaced and it has to be harder on bearings than a 125.

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Ok I think im going to keep it. All my transmission bearings were smooth so I think it will be alright.

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I did a total rebuild on my 98 cr250 when the crank bearings went out.  And I did It all becasue I ride places you don't want to walk out of.  But as somone else said, my old bearings were just fine, except the the crank and the counter sprocket shaft bearing.  My crank actually seized and since it was new used to me I had no idea how it was taken care of so that's another reason I did the whole thing.  Top end bearing/pin and piston without question.

Edited by ramjetV8

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Ok. So while we were putting it back together we noticed that one of my gears in my transmission had a cracked tooth. What does this mean? Will it grenade if I dont replace it?

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Ok. So while we were putting it back together we noticed that one of my gears in my transmission had a cracked tooth. What does this mean? Will it grenade if I dont replace it?

id replace it if it breaks off it could cause a lot of damage

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id replace it if it breaks off it could cause a lot of damage

Definately. I hope you can find it. Check all your other gears closely too.

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Make sure to check all of them for hairline cracks as well all it takes is one bad egg to ruin the whole potato salad know what I'm saying lol

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