Do I have to replace my dirt bike crankshaft?

Question

I own a 1993 Yamaha YZ 250E (two stroke, of course).

I heard a rattle in the crank area and took it apart. The noise was coming from the con rod. The bottom bearing (and pin) is bad. I got a new rod kit, and sent the new rod + the crank to a machine shop.

They measured the different parts of the crank. The part of the crank that sits inside of the mag-side bearing is 2 thousandths of an inch off. (I understood that "off" means that the diameter of the aforementioned part had been ground down to a smaller, non-acceptable size.) I have been warned that it will slop around in the bearing, but others have advised that such a tiny measurement is inconsequential and that I should just reuse the same parts (except the rod kit, obviously). The new part would cost ~$200, a new crank ~$600.

I'm a poor college student and cannot afford to invest much into this bike. Is the shop just trying to sell me an expensive new part? I do not know a lot about bikes or mechanics. What should I do?

Answer 1

there is no set answer.... it could be fine, and it could cause worse damage...

honestly if i were you i'd get a new crankshaft.... think about it... if it does continue to **** up, you'll have to replace it anyways, plus you run the risk of doing even more damage that you'll have to fix.....

Answer 2

How about a complete crank for under 200 bucks? I love those old YZ's.....cheap parts!

Answer 3

my dear, poor college student

a 93 crosser alltogether in running condition (no talking about restored to mint and preseved for collection) is not worth more than $600

you can rebuild with the crank as is and ride until it dies

I would not even pour $100 into this thing, it will constantly need parts, mostlikely the suspension is worn, as are the brakes and frame and ...

I'd try to sell and put the money I save by not having this thing in a newer-dirt-bike-in -good-working-condition-fund