Crank and bearing lifespan

[BrandonH]

Anyone know how to tell if crank or crank main bearings are going bad? I know it depends on how you ride but what is average lifespan.

What symptoms do I look out for. It's not giving me problems but just for future reference. The rod specs out fine no vertical play.

 

[98blaster]

Usually the lower rod bearings explodes an looses the thrust washer before the main bearings ever have issues, I have a pile of cranks that have blown lower rod bearings, its pretty common on a older engine

 

[BrandonH]

So when the bottom end is done, usually the rod bearing goes first. Does that ever ruin anything like the top end?

 

[Awk08]

So when the bottom end is done, usually the rod bearing goes first. Does that ever ruin anything like the top end?

it can depending on how chewed up the thrust washers get before completely locking up.
if they get chewed to pieces and those pieces make their way up the transfers...goodbye topend
i had one take out a month old topend.

 

[Herpderplol]

well consider this. there are some 88-89 blaster on here with stock cranks. that will tell you how long they last

 

[Blaaster]

Lubricate it well with a good oil and it will last yonks.

 

[OConnor Racing]

Connecting rod and bearing life is measured in hours, not years. Anyone claiming to have a 1989 Blaster with the original crank and bearings never rides it.

 

[BrandonH]

Connecting rod and bearing life is measured in hours, not years. Anyone claiming to have a 1989 Blaster with the original crank and bearings never rides it.

That's what I thought. When I had my CR125 I did everything off hours and used an hour meter. 40 hours every top end build and so on.

How many hours do you put on yours before changing?

 

[MercMenace]

When I had my cases open on my 89 the crank was oem. Not sure if original or not. My neighbor machinist friend measured the play and it specced just fine. I replaced all the bearings while i was in there. they seemed just fine tho. no idea how many hours on the crank but it could be 25 yrs old.