Kodiak 400 Blow By

[Yammerhead]

I bought a 93 Kodiak 400. She's a high miler, but it has new pistons, rings and the head has been re-done. I haven't had a chance to ride it, but I have noticed that the motor has a ton of blow by. If I pull the dipstick with it running, there is a lot of air coming out, to the point that it sprays an oil mist out. I checked and the breather that feeds up to the intake is open and air was coming out. How much pressure should be expected with this motor? I want to think it's pressurized to keep water out, but I am guessing that is wishfull thinking. :ORC

It seems to run nice, so I am going to take it for a couple of rides and watch the oil consumption before I decide to tear it down.

 

[maim]

did they bore the jug when they did it? if they put back stock piston and rings on a high mile motor, the jug might be a bit too funel shaped for the rings to seal properly at tdc.

 

[Yammerhead]

I asked that when I bought it and he said that they measured out the cylinder and it was within spec, so they didn't bore it out. I have to think that it must have been worse than he thought. D'oh!

 

[Camo7]

Usually a bore job is required. The tapered cylinder is only part of the problem. The walls to the front and back wear more than the sides because of the pressure created by the connecting rod when it's pushing back and forth as the crank's going round and around. This causes a sort of wave in the cylinder wall that isn't really detected by a simple micrometer.
Could also be that the engine is so new that the rings haven't seated yet. Drive it a bit and see if it improves.

Ian