Chewed up crank seal - cause?

[NYSingh]

Had my engine out of the frame while doing some body work and repainting, figured I'd take a look at how things are looking on the inside. Turns out the crank seal behind the primary gear is all chewed up. Well, good thing I found this before I did more damage.

(1) What could cause this other than incorrect installation? Could issues with the crank (out of balance, out of spec) cause it?

(2) Think I know the answer, but could I replace that seal without splitting cases? Even if I can, imagine I'll need to look to make sure there aren't bits of rubber floating around near the transmission.

[quocle603]

Thats quite strange indeed. The seal could have been shrunk and blown out from a lot of pressure and got chewed up by the primary gear. I know you can only torque down that crank bolt so much and it would not get close to that crank seal. Good time to rebuild and replace them all and do other work to it.

[1976RD400C]

Did someone leave loose change in there?

[m in sc]

check endplay on the crank.

i assume the penny was to you could remove the nut?

[Striker1423]

I used a penny to take the clutch and crank nuts off the first couple times I rebuilt my RD lol. Hard to believe I haven't really been inside that motor in several years already. Knock on wood.

[NYSingh]

Wait, so you're telling me it's not good luck to put a penny in the clutch housing???  (yes, was my poor man's method to loosen the primary gear nut)

I'll get some cheapy amazon special dial gauges to measure the crank's endplay.  But assuming it's not way out of tolerance, I have to think the seal just wasn't seated properly in the grooves in the crankcase and that's what caused it to get dislodged. Just want to make sure I avoid making the same mistake when I re-assemble.

[sav0r (CL MotoTech)]

If the crank is twisted it will spit seals and eventually bearings.

[m in sc]

might have been pused out by a failing crank bearing cage