DT125R ARCHIVE

gasto · DTR Respected Member

Broken crankcase

NORFE · DTR Trusted Engine Builder

it looks like somethings got in between things, like a bolt or some thing when the gearbox has been moving and as its dragged it round its broke where its been weak

or a spacer.shim in the wrong place on installation and as the cases have bin tightened together its broke the case

all inturnals are hardened steel and the cases are soft alloy the alloy will fail b4 any of the drive train

confuse

gasto · DTR Respected Member

I still haven't disassembled the engine(the pic is from a friend that have the same problem).What i have noticed is that the original bearing that yamaha gives for the shaft has something like a spacer on it and mine that is changed doesn't have that,so maybe the crank gear wasn't working right with the clutch and that caused that.On the other hand maybe something go wrong in the gearbox.

gasto · DTR Respected Member

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Everything seems ok in the gearbox.Still can't find why that happened.

RudiRulez · DTR Senior Member

you sure that replacement bearing is exactly the same size as the original? how did you get it in, pressed, hammered, or heated?

the only way is YAMAHA DTR · Guru

sometimes castings have airbubbles in them making them prone to crack,

can be welded, but by the time you have the bearing seat machined, it would cost less to get another casing

gasto · DTR Respected Member

The bearing was the right one and had it pressed in.Already bought another bottom end.

mr karnage · Guru

does the crack go through to the other side?

its cracked right where the bearing retaining plate bolts into

gasto · DTR Respected Member

Yes.When i opened the cases the bearing came out with no pressure.

mr karnage · Guru

i bet someones been doing some hard downshifting