What's that hose coming from the airbox

[samamoto]

I noticed that I lost about 1qt of oil over last 3500 miles. I started to look around for possible leaks. I found quite a bit of oil sprayed between engine block and air box and final drive. Looking closely I noticed the oil is most likely coming from the air box, the nipple that is supposed to have hose(17), oil filter(18) and another hose(19) connected. I do not find that hose/filter assy on my bike. It's not attached and I cannot find it hanging anywhere. What is it for? Is that an oil vent from the crankcase to the airbox or vent out from the airbox. Or maybe something even different? Do you think it may be the source of the slow oil leak or should I be looking deeper? Is it supposed to be connected somewhere at the bottom? I definitely see there is oil droplets forming on the nipple where hose(17) should be, I'd guess the quantity could roughly match what I lost over the mileage but not sure if it is a source of the issue or result.

 

[Cyclepath]

I'm pretty sure that airbox hose is there to equalize pressure with the crankcase, just as with automobile combustion engines.

 

[samamoto]

That's what I'm also thinking it may be. I'd like someone to double check where it goes to and than hopefully someone smarter than me to tell me that could cause the loss of oil.

BTW, if that's the case and that hose is there to recirculate the oil from the crankcase two questions arise: 1) does 1qt of oil circulating through there seem not excessive? 2) should I be worried about having that went/circuit disconnected for the sake of both proper case working conditions maintenance and crap finding it's way in there?

 

[Boston]

mine just hangs down under.

 

[Cyclepath]

When I said "pressure" - I meant air pressure.

 

[RossKean]

Don't think there is (or at least there shouldn't be) any oil coming from the airbox. It is normally dry inside. Note: The plumbing is different (parts 30-33) if the bike was built for the California market.

Did you recently do a valve check - may not have the valve cover gasket properly installed??

 

[Fred W]

Crankcase vent is hose #27. It runs from the crankcase to a larger nipple up between throttle bore #2 and #3. Im pretty sure that the hose you are missing is a drain line for any moisture or oil that condenses and accumulates in the air box. Oil present on that nipple would be from blowby entering the box via hose 27.

By having the hose missing your airbox has also been allowing unfiltered air into the engine through that nipple. That is not a good thing. You are going to want to check your engines compression and/or leakdown to see how much damage was done. And replace the missing vent line components or at least install a length of tube with a plug in the end that you can open to drain any oil from occasionally. That is how some manufacturers design their air box drains.

 

[Geezer]

How many miles on the bike and how hard do you ride it?

If it is leaking almost a quart in 3500 miles you should see at a minimum oil stains under the bike, and likely a puddle, when parked. If that much were coming out of one place when riding there should be quite a lot of oil splashed around where it is leaking. Otherwise the oil may be going out the exhaust. You might see blue smoke in the exhaust and possibly oil on the end of the mufflers.

My '05 with over 150k miles on it uses close to that much oil if I run it very hard with a lot of compression braking. I do not see blue smoke, but it only uses oil when running hard, and I am not looking at the exhaust while doing that. In my case I suspect the valve seals and/or guides.

 

[samamoto]

Bike has 78k now and is scheduled for the valve check next week. When doing so I already requested to get the oil loss checked. This is the first time I'm seeing the oil consumption on this bike. Up until now it was always pretty much sealed. No puddles when standing, it seems to be a result of riding. Yes, I push it quite a bit and I do a lot of compression braking - didn't change the braking pads in forever and they still have plenty of meat left on them. When looking around it I don't see any other obvious leaks or places where oil could drip from other than the left dog bone pretty clearly being fed from the airbox missing hose.

I'm leaning to shift the priorities, ask to make the leak down and compression tests, see if the engine is still worth the effort and only next do the valves. Being an 06AE with almost 80k miles bike has more of symbolic market value and if the engine starts to fail I may need to explore secondary options.

 

[Geezer]

I understand that it is not worth fixing if it is worn engine parts. I do not intend to tear into my engine. I do intend to keep riding it. I don't ride often enough these days to justify a new motorcycle. I carry a quart of oil when I'm on long rides so I can top it off as needed.

 

[Stickboy]

Bike has 78k now and is scheduled for the valve check next week. When doing so I already requested to get the oil loss checked. This is the first time I'm seeing the oil consumption on this bike. Up until now it was always pretty much sealed. No puddles when standing, it seems to be a result of riding. Yes, I push it quite a bit and I do a lot of compression braking - didn't change the braking pads in forever and they still have plenty of meat left on them. When looking around it I don't see any other obvious leaks or places where oil could drip from other than the left dog bone pretty clearly being fed from the airbox missing hose.
I'm leaning to shift the priorities, ask to make the leak down and compression tests, see if the engine is still worth the effort and only next do the valves. Being an 06AE with almost 80k miles bike has more of symbolic market value and if the engine starts to fail I may need to explore secondary options.

Taking a quick look at your plugs will tell you if it's burning oil. If they are black and oily, they are burning oil. Normally plugs should be a tannish color. Flat, carbonny black means it's running rich, and that is likely not related to your issue.

 

[dcarver]

By having the hose missing your airbox has also been allowing unfiltered air into the engine through that nipple.

That's very true.

 

[samamoto]

I'll see if I find a moment and tools to remove and check the plugs before the service. I'll definitely need to replace that hose.

 

[kmanflyer]

"I'm leaning to shift the priorities, ask to make the leak down and compression tests, see if the engine is still worth the effort and only next do the valves. Being an 06AE with almost 80k miles bike has more of symbolic market value and if the engine starts to fail I may need to explore secondary options"

I think this is a good plan. But instead of pulling the spark plugs, (since the shop will have to do that to do leak down/comp test anyway), they can check the plugs while they have them out. I would pull the air filter out and check for crud in the air box with a mirror and try and clean it out as best as possible. Then definitely put a hose with a cap on the end like Fred W described, to close up that open hole. At least it won't be getting any worse and might be able to determine how long the hose was missing by how dirty the air box is. Just more information along with the leak down/comp test to evaluate the situation.

You can get the OEM hose setup with the filter after the testing/evaluation. Good Luck, hopefully it's not too bad.

 

[dcarver]

My bet is compression and leak down will be fine. I rode with a major air leak for 20k + miles on 6 miles of very dusty dirt road daily before an issue popped up. And since no autopsy yet, can't say the dirt did the first KrZy8 engine in.. it had water leakage into a cylinder.

 

[Geezer]

My bet is compression and leak down will be fine. I rode with a major air leak for 20k + miles on 6 miles of very dusty dirt road daily before an issue popped up. And since no autopsy yet, can't say the dirt did the first KrZy8 engine in.. it had water leakage into a cylinder.

I agree with Carver. I don't think a small amount of dirty air is going to make a noticeable difference in the engine unless there were some very dusty conditions or sand flying.

Back to the disappearing oil, I would expect that a large amount of oil leaking out the back of the engine would show on your pants or even the rear tire. Since you said that you do ride the FJR hard, then you would know if there was any oil on the tire.