crankcase breather blows oil

on my kz750e2
I get blowby out of the Filter I have attached to the top of the breather under the carbs, at higher rpms through town today (bombing light to light) it seems to have an issue of blowing oil out through the filter all over my engine and down the left side.

is it because i have the filter mounted directly on the hole? are they supposed to be mounted higher via a Hose?

This thread was posted a year ago by KZJohn. Seems like the KZ community was thinking the cause may have been a compression problem....

kzrider.com/component/option,com_joomlab...id,2/id,22973/#22973

thanks.
im not doing any engine rebuilds here, open patio, no garage, only have a tent awning.
looks like i will just run it until i sell it.

i am capable of refacing crappy looking bikes, but not interior motor issues.

You know, I think I read somewhere that overfilling the crankcase will cause blow-by. You didn't fill the oil while the bike was on the side stand, did you?

:whistle:

no, always on the center stand.
it never did it before until now that i parked it since last summer, i am going to D&R the oil soon when i get a bit of spending money again.

I just got 10 feet of bulk plug wire at napa and holy crap! dont spin the throttle without holding the seat firmly with butt cheeks. the 750 seems to have a 0-55 in 1st gear in less than a couple seconds when it fires properly and all warmed up, my kz900 isnt so quick off the line.

Has a compression check been done (spin over at cranking speed with throttle held wide open).

Next, put teaspoon of motor oil in spark plug hole and repeat compression test.

Any difference in the numbers?

If the second test (with oil added) shows significantly higher compression, indicates "blow by" past the compression rings, into the crankcase, and out the vent pipe.

Here's some speculation. Sometimes while standing unused for quite awhile, piston rings can become frozen (stuck) in their groves around the piston, which prevents them from doing their job. This process may be aggravated where any fuel leakage through the carb into the cylinder combustion chamber has flushed the residual oil from the rings. For example, when the petcock is left open and the float needle is not properly seated and float bowl over flow tube is clogged.

Recall reading somewhere that Yamaha has a special oil designed to help free up frozen rings, but perhaps any light weight oil would suffice, and maybe PJBlaster would work. The idea is to put it inside the spark plug holes and allow it to soak for a few days or longer.

Would also change the oil and filter to assure crankcase oil has not been diluted with fuel (and causing excess venting action).

Running the engine with frozen rings may damage the rings beyond recovery and thereby require new rings.