New bearings or not??

[cr2504life]

     

Hey guys,
I have a pretty simple question. I bought new crank bearings for my bike after I got my damaged cases “fixed”. Well I did a leak down test and found that the cases were still leaking. I just purchased new cases and I was wondering if I should buy new bearings or can I use the ones that are in my damaged cases. When I tried to repair the cases I bought all new bearings and seals. I am going to buy new seals because I will probably damage them trying to take them out. Thanks for any input.

[ossagp]

Very likely you can warm the old cases and get the bearings out without damage. Just see if they turn free.

[E-man811]

I would highly discourage re-using crank bearings. First, when they are pressed off of the crank, you are putting tremendous side loads on the inner race, which transfers to the outer race in stationary concentrated places. In effect creating dimples in the sides of the inner and outer races. You cannot see them, but they are there.

It would be absurd to not put $15 crank bearings on a crank if you have it apart. This is not an area to cut corners. Especially if you have it apart because the crank nuked in the first place.

Consider that crank bearings only last a few years with perfect surfaces. I have seen them frag rather quickly with compromised surfaces.

If it's not too late. Put new bearings in it.

Ian

[ossagp]

didnt read his whole post, did you Eman?

[E-man811]

ossagp.... What did I miss?

Here's the chain of events that I took from his post.

-Cases damaged, bearings pressed off of crank to dis-assemble
-Cases repaired and new bearings installed and engine assembled so a leak down test can be performed. Unless this was done without the cank in the cases????
-Cases leaked so dis-assembled again (bearings pressed off of crank)
-New cases purchased, "can I use the bearings from the damaged cases"....

If they were on and off of a crank then the answer is no.

Help me if I'm off the mark.

Ian

[ossagp]

Ok,,i see you did read it all. I disagree that his bearings are necessarily damaged. Your remark about the crank being nuked led me to believe you did not understand that the bearings newly installed .

I can understand you or anyone being nervous about bearings that were pressed on or off. I did not see any place were a press was mentioned. Many of us know how to get them on and off without a press.

Having used lots of bearings over time and having represented companies to industy who manufactured them has given me a pretty good understanding of them. In this application the factory specified bearings are designed to take up some misalignment. They also have very little side load. Not even the amount that your wheel bearings do.

If you have doubts,,,replace,,,but I am confident I could have installed his and reused them. Simple as that.

[ossagp]

Oh,,by the way Eman, You and I agree on assembling cylinders dry. I go the other way on hones though,,,i go smaller on the hone than the bore. It seems to keep it out of the ports for me and keeps from damaging the edges,,,you just have to develope a "move" when you use it to clean one up,,which is all you are really doing. In 2003 the K'w were still trash on the plating in my opinion,,and that is the last one I have been in.

[E-man811]

ossagp


I agree with you on all points. Done the right way, new/low hour bearings can be re-used.

I didn't intend to debunk your original advice. Given the way that most of the less informed split cases/remove crank bearings and the typical amount of time before most people's crank bearings see the light of day, I wouldn't recommend re-using bearings. As a default for most people, replace them.

The crank nuke comment, I meant to make a note that it didn't apply to him. My bad.

Ian

[ossagp]

we are on the same wave length. though i dont take in work anymore,,i am willing to do things on my own rides that i wouldnt on someone else's.

nice to have you here

[kickindirt114]

I would go with the new ones.