Oil Level Fluctuation :S

Well i am having what i think to be a problem. I have a 75 Kz900 that i was recently given. It had been stored for atleast two years before i got it and did everything to get it running. I now seem to have a problem with the oil level in the sight glass fluctuating. I have drained the oil completely cold and hot, and upon refilling to spec the bike will start and oil level will be fine, as the bike runs the oil level will completely fill the site glass. I have been told that it might be that gas is propelling itself past the pisons to the crankcase but if this was the case wouldn't the oil smell/ignite upon draining(which it does not)?

Any help would be great as i am completely clueless to this matter.

Pretty hard to imagine what could be happening there. I dont think you would get gas going pass the pistons unless you have very poor engine performance and as you said there arent any fumes on the oil. Did you say that you dont see a good oil level through the sight glass when its off?

does it go back to normal after bike sits?

The oil level will not go back at odd ball times, just because it sits doesn't change it, it is quite wierd. There is no lost performance i just wanted to make sure that there is nothing wrong.

I didnt want to ask this question but are you checking your oil with the bike standing up straight? sorry for the silly question

I am not sure but it sounds like there is some kind of pressure just blocking the window, preventing the oil from showing in the window. try starting the bike when you dont see the oil and see if it appears when you crank it. now there is advice lol sorry about before man

This happened to me several times last year with my '79 kz650. I would just change the oil and fill it to the proper specs- then notice a few days later that the sight-glass was full. Turned out that my petcock was bad. I had the crummy vacuum kind which you couldnt turn off and gas was seeping through into my oil.

I bought an older kawa petcock on ebay with a manual shutoff, rebuilt it (it was trashed internally), tap and die'd my tank, and installed it. Now I religiously shut off my fuel just before turning offf the engine. My oil level has never fluctuated again:cheer:

Hope this helps

-pueblo colorado

Post edited by: bigkaw815, at: 2006/10/10 21:47

well the petcock does leak a bit maybe this is the problem not sure. As for checking the oil on the center stand yes i do (and no problem for the "silly question" )

You may already be way ahead of me on this, but if a float bowl overflow outlet or tube is blocked and the float is stuck or the float needle is not seating and allowing flooding into the carb (or for whatever reason excess gas is getting by the float needle), the excess gas getting by the float needle can back up into the stock air box and drain down through the crank case breather tube into the crankcase (which is definitely not a preferred manner for raising the oil level). Of course, a properly functioning pet cock turned off should prevent such flooding when the motor is not running, and even an open or leaking pet cock while the motor is not running should drain flooding float bowls through the overflow tube. But while riding the bike, you may not immediately notice a problem until the gas-diluted oil starts causing excess exhaust smoke from the exhaust. (Trust me, it happens, and thank goodness for low pressure roller bearing cranks). Bikes with smoothbore carbs are particularly vulnerable because they have no float bowl overflow drain facility, and when flooding for whatever reason (stuck float or leaking float needle), the excess gas backs up into the air box and manages to drain back down through the crank case breather into the crankcase oil. To avoid this with smoothbore 29's, I simply disconnected the crankcase breather tube from under the airbox and re-routed it downward and underneath the bike, and keep a close eye on the float and float needle operations. It is truly scary draining hot watery thin gas-diluted oil late at night in a convenience store parking lot, refilling with the cheapo stuff and limping home. Riding at night, I didn't notice the smoke, any unusual noises or motor trouble, and was just lucky having a riding buddy behind me who noticed the smoking exhaust and waved me over before any real damage was done. Yes, the airbox has another separate drain hole, but unfortunately the excess gas backing in from the flooding carb manages to first drain down into the crankcase breather hose. Anyhow, that's my personal experience about having and solving the problem of gas getting into the crankcase of a Z1 with 29 smoothbores. Happy trails.