Leak-down test, new seal, still not holding pressure

[ElFuegoBlanco]

I finally got some time to get back at it. I replaced the crankshaft seals (76 RD400) with genuine Yamaha seals. Engine is reassembled and I did another leak-down test before installing it in the frame.

It's still leaking at the left side seal. It goes from 5psi to 3psi in about 20 minutes, then to zero some time later. Where do I go from here? When I manually turn the crankshaft, the leak remains at the same two places on the seal (around 2 and 6 o'clock).

Is there anything else I can check or do? Or am I just looking at at crankshaft rebuild here?

Thanks, Rob

[ElFuegoBlanco]

I split the case yet again. Cleaned everything up, reseated everything, and I think I'm finally good to go.

[pidjones]

Good! What was the culprit?

[ElFuegoBlanco]

Good! What was the culprit?

I think some very small corrosion on the crank end. I hit it with some 2000 grit sand paper. That or maybe it just wasn't seated quite right. I tapped on the crankshaft a few (more) times before mating the case halves with a rubber mallet.

[rodneya]

If the leak stayed in the same spot after turning the crank you most likely has some crap stuck in the seal.

[m in sc]

agreed. well, sorted is sorted, good job. 

[ElFuegoBlanco]

agreed. well, sorted is sorted, good job. 

Now back to the original problem of tuning a basket case "parts bike".