Crank Seal failure

[carhartt]

I have a Partner K970 I built for a neighboring landscaper. He passed it back with "it wont run" scenario. I took a look at it and tore the carb apart to many times. Then said I needed to take a look at the crank seals. Not one but both seals where destroyed. I mean not just worn out like most of the rubber seal was missing. I pulled the seals and replaced them. I got it all back together and running fine again. next day before I called him to come pick it up I tried it again and couldn't get it to run again. I checked a few things and then back to the seals again. One of them are blown out again. What would cause pressure in case to push the seals out?
compression 150 psi
carb cleaned to many times
no other air leaks

 

[tallfarmboy]

I would guess that your crankshaft bearings are shot. That is allowing excessive play on the shaft and is destroying your seals. Check to make sure the bearing cages are intact and that the balls on the bearings are spaced properly around the bearing.

TFB

 

[carhartt]

The seal retaining ring is still in place. It is just the rubber seal portion the is being pushed out. It has to be a pressure of sorts. The crank spins freely so I don't think the bearings are shot. Not saying I haven't been wrong before. I will dig into it. As you can see I am trying not to split the case again.

 

[jeff taswelder]

opcorn:

 

[chrisoppie]

Piston in backwards? how about the impulse line in to the cylinder (not sure if this model has one) ? muffler crushed in?
If the bearings are "good" some where your getting not enough escape of pressure where it is supposed to be.
I have worked on a few k750-760 tricky little buggers.