Rings or valve seals?

When i rev the motor on my 81' KZ1000, a small amount of black smoke comes out (indicating a rich mixture). when i let off the throttle the RPMs go down and right as its hitting idle it belches out white oil smoke. all my spark plugs look good. It runs good but doesnt seem to have the power it did last summer. any ideas on what might be wrong?

Thanks guys,
KT

A simple compression and leak down test would verify that it is the rings.

fun stuff i will go cry now. nah ill rebuild it this coming winter. cylinder 2 is getting about 90-100 psi compression. thats not very good.

Sorry to hear that. How did you perform this test? Throttle open?Engine cold? Dry cylinders?

i know on a car worn valve seals guides will make smoke on decel and worn rings will make smoke on acel however as others say a compression test will show whats up ..

I never said it wasnt valve seals, I just recommened a compression test.

Kitten Tooth wrote: fun stuff i will go cry now. nah ill rebuild it this coming winter. cylinder 2 is getting about 90-100 psi compression. thats not very good.

If you can swing it also do a leak down test. That should help verify if it's the rings rather than possibly a valve. Ed

I rebuilt my top end last winter. It wasn't as hard as I was expecting. My valves weren't sealing up well. Had about 90 psi in Cylinder No. 1. For parts I paid $250 for rings, gaskets and viton guide seals. I also had to buy a bunch of specialty tools that set me back more than that, but now I've got them forever. I'd say the most time consuming part of the whole job was scraping the 31 year old gaskets off the deck. Good luck on the rebuild.

I'd bet on rings. Valve seals leak a pretty constant amount of oil and will typically puff on start up but not so much puff up when revving. That sounds more like rings, although both could be bad.

Spectre1982 wrote: I'd say the most time consuming part of the whole job was scraping the 31 year old gaskets off the deck.

Yep. I recall it was 3 or 4 hours removing the base gasket under my cylinder.