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Main crank bearing play. 1150 crank

  • Thread starter Thread starter cdnoel
  • Start date Start date
C

cdnoel

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Probably a question I should be asking a crank specialist but I figured one might chime in here. Just purchased a crank and it checks out on most all of the measurements I've done on it.
44mils average of play/wag measured from the rod ends.
.7mils of gap between the rods and journals.
Most of the main bearing have less than one mil or 1/1000 of radial play when lifted up and down.
Most except the one next to the main clutch drive gear which has 2.5 mils of play. New bearing in order? would like to find the specs on this thing if possible.

Not surprised that the bearing next to main drive gear would have the most slop but if it's well within specs I might just call it good. The alternative being having the welds ground out of the thing and rebuilt from scratch.
 
cdnoel said:
Probably a question I should be asking a crank specialist but I figured one might chime in here. Just purchased a crank and it checks out on most all of the measurements I've done on it.
44mils average of play/wag measured from the rod ends.
.7mils of gap between the rods and journals.
Most of the main bearing have less than one mil or 1/1000 of radial play when lifted up and down.
Most except the one next to the main clutch drive gear which has 2.5 mils of play. New bearing in order? would like to find the specs on this thing if possible.

Not surprised that the bearing next to main drive gear would have the most slop but if it's well within specs I might just call it good. The alternative being having the welds ground out of the thing and rebuilt from scratch.
Click to expand...

If that's 2.5 millimeters of vertical play...then oh my yes, replace.....
If it's .025 millimeters, you're OK
 
Thousandths

Thousandths

Sorry I usually speak metric but my buddy who has machining tools and helped me figure out the wear uses the English system. 2.5 thousandths translates to 0.0635mm in our world.

The other 5 main bearings only have 0.0254mm of play or less so the one in question is two and a half times as sloppy. Still trying to figure out if this is acceptable.

Manual says to check
1. run out, or over all true which is fine.
2. Main journal gap which is fine.
3. Axial play on main journal to rod which is fine.
other than that the manual leaves me hanging.
 
.0025inch is just acceptable on a roller bearing. Some modern roller big ends come as std with up to .006in clearance.
I'd be more interested in having a close look at the races for any pitting. If any can be seen, it's replacement time.
 
Thanks.

Thanks.

Thanks.

I'll have to see if I can peek at the races at all. They feel smooth but will only slide over so much before they run into the side of a crank throw.

The two center bearing races will slide clean off and rattle around on the cam gear. Happens to be the way the seller shipped the damn thing to me. Fortunately the races are of a harder material and I don't think they would have suffered an impact hard enough to dent them in shipping. Would have taken a hammer or some direct blow to do that.

Note to self. Ask the next person I buy a crank from to park center races on the bearings and away from the cam gear.

I'm considering having the crank balanced as this would probably reduce wear on the bearings from this point forward. Don't want a thousand dollar crank service though.
 
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