I think my crank is smoked.

[Striker1423]

Hooray!

I should have checked this before. 

So, if I remember correctly, after you clean and flush out the crank , one should test the bearings in the crank for any funky noises right? So, you spin the bearing dry correct? Brake kleen and a few spins later. Well, I think mines got issues, here's a video.

The crank sounds fine with a drop or two of 2t oil in each bearing. Which, well, makes sense.  This project jumped a level in expense I wasn't anticipating.

[Greaser Greg]

I spent most of my money on bikes, broads, and boats, and wasted the rest.
Welcome to the club!

[pidjones]

I would never spin a bearing, even in testing, in a totally dry state. With some light oil, it should be silent.

[Striker1423]

I would never spin a bearing, even in testing, in a totally dry state. With some light oil, it should be silent.

It is quiet with a drop of oil. Is this not a good way to test? 

[Milan]

I agree.

Bearings should not be run dry.

Even new, the Mfgr has some grease or lube in them.

Sealed bearings are sealed with the lube inside, so as to never lose it.

put the same lube in it, that it is exposed to inside the motor.

M

[m in sc]

axial play is what matters. put a drop of 2t in it and check. 

[Striker1423]

What should I check for? Should it be no play?

[scully]

Most two stroke cranks use C3 bearings.....C3 Bearings are loose to the feel from new. new bearing C3 radial play value between .0006" and .0010"..Axial play is approximately 10 times the radial play value.

[bitzz]

/quote]

It is simple to tell if a bearing is bad.
We, as mere mortals, have no test to tell if a bearing is good.

If the rest of the crank is in spec, replace the outside bearings (they're cheap and easy) and hope for the best.

[m in sc]

scully is of course correct. hence also why i said what i said.

side to side wobble will indicate easier as bad than up and down will, usually. 

[NYSingh]

For comparison, here is the sound of a brand new bearing https://www.youtube.com/watch?v=zBVnCVHmGmo

Having never replaced bearings before, I thought even this new one was too noisy so asked 2sw (old site) and was told it's fine!

[1976RD400C]

I suppose you could take a light and a magnifying glass and look carefully at the races and balls to see if there is any sign of anything that is not perfect.

[sav0r (CL MotoTech)]

Unless there is a defect of some type the rod bearings are far more likely to fail before the mains.

[m in sc]

i disagree. the RH drive one sees the most wear on any crank i've pulled down, then the alternator one, then the rods.

[pidjones]

i disagree. the RH drive one sees the most wear on any crank i've pulled down, then the alternator one, then the rods.

That's what I found on my 400. Alt bearing was smooth as can be, centers felt Okay, drive bearing was obviously (to me) rough. Lyn Garland rebuilt it for me and they were silky again.