Airfilter & Oil

Hey guys, I have a 1980 kz550 ltd.
I just recently ripped some junk pods off the carbs and purchased a used air box. I connected the air-breather from the engine case to the bottom of the air box when I installed it. The funny thing is, I have oil in the bottom of my airbox now. Does anyone know why that is?
What is the benefit to having the breather hose connected to my filter box, as opposed to running a rubber tube to the outside of the bike, like the carb overflow hoses do?

Possibly overfull on oil in the crankcase, also blow-by past the piston rings will cause this.

A fine mist of oil is normal, but if it is more than that, likely causes are ring blow-by or a grossly over-filled crankcase. I believe the main advantage to venting into the air box is a reduced likelihood of dirt and such entering the engine through the vent. Then there's that air pollution bidness............

Yeah, I'm doubting that I have too much oil in the bike, but that is a much more desirable possibility than blow by. I totally forgot about that. So I would connect an air compressor up to the spark plug port and turn the timing bolt till I had the highest possible pressure, and then listen for gurgling or hissing in my case... yes?

That will work. If the 550 is like the litre engines, be sure to turn the engine over with the large nut, not the small one.

A compression test, followed by a leak down test if low, will determine where the problem lies. Here's a HF link to a leak down tester.
www.harborfreight.com/automotive-motorcy...wn-tester-94190.html

+1 on the 17mm large nut on the right hand end of the crank for hand turning. You need to place each piston at Top Dead Center Firing position to check with the leak down tester or your compressed air. If the air is already applied, you won't turn it far, or it will turn its self, with your wrench and hand on there it might get nasty.

You will always get some blow-by with a leak down test, as it is just air passing the ring gaps. Listen and check for same constant pressure with constant input pressure. If one cylinder is much lower, then you have an issue.

Don't use too much air pressure, as this can cause the crank to suddenly twist and possibly wreck the end bolt or you with whatever tool you have on there.

Don't use more oil than 2/3 from bottom of the height of your oil window.

...and dont worry about it too much if the bike screams. :laugh:

The harbor Freight leak down tester is JUNK! I owned it! Go with Snap-on, its $$$, but works fantastic.

The reason for the use of a gauge in a leak down test is to determine not only where the pressure is escaping, but what percentage, usually of 100 psi, the cylinder will hold. Yes there is always some air that goes past the rings, but how much? This when oil is added to the cylinder via the air line fitting already in your plug hole, if using the tool.
Compression test first followed by leak down, industry standard.