Oil coming out of my float bowl overflow?

Just did a service to my '78 kz1000.
- new oil and filter
- remove/clean carbs
- check valves
- has good electronic ignition, no points etc.


Took her out, ran find then started intermittently not firing on all 4.

So when I parked her I did 2 things:

- found the plugs on 2 and 4 were really sooty
- and -- first time in my life I've seen this -- OIL dripping out of the tubes that connect to the bottom nipple on the float bowls -- I'm going to assume these nipples in the center bottom of each float bowl are overflows for the carbs...?

So I pulled out my brand-new stock air cleaner filter element and -- my new filter was oily at the bottom.

I then found oil in little puddles at the bottom of the air filter element box and used up 2 paper towels getting most of it out -- there was a LOT in there.

What could be going on? I know that the oil is fouling my plugs to explain the sooty plugs and the cylinders intermittently not firing -- but why oil in the carbs?

I notice a black hose from the bottom of the air filter box to the top of a big round cup-like extrusion on the top of the crankcase to the rear of the cylinders and above the gearbox and clutch.

What's up with the oil in my carbs?

that would be crankcase breather, oil into airbox and then into carbs ??? a lot or a little oil ???

u said new oil, how much ???

Probably I overfilled it?, it kept going up above the site glass at the bottom outside of the clutch cover. "What could a *little* extra oil hurt" I thought.....?
Do you think that's the problem, does excess oil come out of that 'breather' and ......INTO THE AIRBOX?! Why would oil be designed to dump into the airfilter, which will be ruined by the oil.

u overfilled it.with bike level,oil should be no more than 1/2 way up on the sight glass. oil is being blown thru breather hose into ur airbox.bj

You need to remove some oil for sure! You can use a thin piece of clear tubing to syphon some out through the filler cap (ask how I know :laugh: ). The oil level should be between the 2 marks on the site glass, maybe 3/4 of the way toward the top mark. But let the bike sit a while before filling it that high as sometimes it may take a while for it to show up in the site glass. Normally, the breather goes into the airbox were the vacuum of the airbox will gently draw fumes from the crankcase up to be burned through the carbs. These fumes may normally contain microscopic oil particles - no biggy. But when pure raw oil is pumped though the breather due to overfilling it will make a mess. Ed

ed +1

650ed wrote:

You need to remove some oil for sure! You can use a thin piece of clear tubing to syphon some out through the filler cap (ask how I know :laugh: ). The oil level should be between the 2 marks on the site glass, maybe 3/4 of the way toward the top mark. But let the bike sit a while before filling it that high as sometimes it may take a while for it to show up in the site glass. Normally, the breather goes into the airbox were the vacuum of the airbox will gently draw fumes from the crankcase up to be burned through the carbs. These fumes may normally contain microscopic oil particles - no biggy. But when pure raw oil is pumped though the breather due to overfilling it will make a mess. Ed

Okay, 'too much of a good thing' in this case. The cool thing is I had just finished re-jetting for the 4-into-1 and modified airbox (the prior owner made these intake and exhaust changes and didn't rejet and before my recent work the bike had been running lean) and went to check that work yesterday for the first time, and the bike was running SO much better than before the tune-up and rejet it was great (for about 30 seconds). I mean like night and day. So I'm half convinced my valve adjustment/carb clean and rejet etc. was a success.

But then the oil started traveling up that breather into the airbox yesterday, and it affected the bike's power (fouling the plugs).

In other words, the overage of the oil prevented me from getting a conclusive feel of whether my valve adjustment/carb clean/rejet was successful -- the plugs started fouling pretty quickly. Yesterday I had just a short distance of much-better-than-before power -- then plugs fouling.

So here's a follow-on question. After I drain the oil out tomorrow, then adjust the oil level to between the 2 marks in the sight glass, I'd like to temporarily re-route that crankcase breather with a hose, routing it downward like the carb overflow tubes and battery vent hose are set up. Then run the bike for a short time to check the success of my recent tune-up work. That way, any additional leftover oil in that breather line won't get sucked into the airbox. After a few miles I'll reconnect the breather tube to the airbox as normal.

ALSO: since oil was coming out of the carb overflow tubes -- should I remove the carbs and clean them out again?

re-clean carbs??? YES

Yes. Clean oil residue out of the carbs and the breather hose. You don't need to reroute it though. Just get the oil level correct, reassemble carbs and airbox.

Did you pull the screens out of the airbox? Because if they're still in there, oil will be coating them as well. I would pull them and leave them out.

larrycavan wrote:

Yes. Clean oil residue out of the carbs and the breather hose. You don't need to reroute it though. Just get the oil level correct, reassemble carbs and airbox.

Did you pull the screens out of the airbox? Because if they're still in there, oil will be coating them as well. I would pull them and leave them out.

I noticed screens covering the large holes that lead to the intake mouths of the carbs. Based on your recommendation I will pull them out and clean them.

I'm wondering if I should discard the brand-new air filter element -- a small line around the bottom of the element is oily. It's easy to see the oil - the brand-new filter element is a white paperish-foam-looking sort of stuff so the black oil stands out. The oil that got into the bottom of the airbox from the breather must have splashed up onto the filter as I was riding the bike yesterday.

Gasoline is an excellent oil removing solvent. I would say "no" to re cleaning the carbs, unless you have a reason to suspect something other than oil got into them. Fuel should flush out the oil, maybe just open the drains and let them flow. Every time you dissamble the carbs, you run the chance of messing something up. Human error and all that...