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Where are common oil leak locations?

x01660

x01660

Mod on a Connie in a neighborhood near you
Member
Well, I've got a leak. First time around, it was from the spin off filter being a tad loose. Now, there's a drip of oil all under my bike.

I took the belly pan off, and it looks like the oil is coming from somewhere by the airbox? I also noticed that the engine-facing side of my clutch side carb has what looks like oil misting on it. There's also old oil that's on the shock.

This started happening after that jerk kicked over my bike.

The belly pan had oil residue on it on the clutch side, from the reservoir location all the way back. The oil appears to be dripping off the back of the belly pan onto the ground (I park on a slight incline).

Oil level is where it should be.

Ideas where I can start? Gonna probably have to pull the middle fairing as well, but wanna know if there are some common leak spots that I should be looking for.

Thanks!

-x01660
 
Well, off the top of my head I'd say any drain hole with a washer, so that's two, I have a drip lower right side that drips onto the header making a little smoke on start-up. I guess if you want to, pull the belly pan, spray some degreaser all over the bottom of the motor, brush it good, hose it off after a minute or so and then look after a short ride. I would not call this motor one that has common leaks as it's uncommon really.
 
If it's ever been overfilled with oil, it will get sucked in the air box and you'll see it come out of the elbow on the bottom. The seal on the water pump can fail. Oil pan gasket can leak.

My favorite YouTube mechanic, Scotty Kilmer, says there is a kit with dye that can help find leaks. Put the dye in the oil and then use an ultraviolet light to highlight the dye as it's leaking out. HTH
 
Sorry, trying to remember, it's been a few years...
Isn't there a hose that goes from the valve cover to the air box? Normally it only had oil vapors, but when it was kicked over, liquid oil could've gotten in there and is now trickling out.
 
Bud said:
If it's ever been overfilled with oil, it will get sucked in the air box and you'll see it come out of the elbow on the bottom. The seal on the water pump can fail. Oil pan gasket can leak.

My favorite YouTube mechanic, Scotty Kilmer, says there is a kit with dye that can help find leaks. Put the dye in the oil and then use an ultraviolet light to highlight the dye as it's leaking out. HTH
Click to expand...

There is an elbow that's visible under the airbox, on the clutch side, and that looks like the upper terminus of where all the oil is coming from, so I'm thinking its that elbow...

I LOVE Scotty; dude is funny. Some of his advice is meh, but most of it is great! I'll grab a dye kit to see what's up.

Thanks!

-x01660
 
I wonder if it's possible that from the bike being on its side, that oil got into the airbox from the crankcase vent and the leak you're seeing is oil draining from the airbox?
 
+1 what Steve said...

But I also had a very minor leak at the left side engine cover where the stator wires went in.
 
Konehead34 said:
+1 what Steve said...

But I also had a very minor leak at the left side engine cover where the stator wires went in.
Click to expand...
Me too . At that square grommet . Bought the whole wire assembly as the grommet is attached to the wires . I had tried rtv first but that did not last long .
 
Wish they would have made those grommets out of something that didn't dry up and shrink.
 
Mine is currently leaking from the left cover after doing a valve job. Can't get it to stop. Probably just going to slather the underside with some gasket epoxy eventually.
 
I found where the leak is coming from; there's an elbow under the airbox on the clutch side that is off of the airbox, and that entire area is covered with oil.

That said, is it normal for there to be THAT much oil that comes out of the airbox? Seems a bit excessive. I'll take some pics later and post.

-x01660
 
It's most likely the tip over contributed to past years of over filling with oil. Clean it up and make sure it's not over filled in the future. I'd bet that issue goes away.
 
Bud said:
It's most likely the tip over contributed to past years of over filling with oil. Clean it up and make sure it's not over filled in the future. I'd bet that issue goes away.
Click to expand...

Any things to avoid while cleaning? Is it safe to go to a self carwash and use the pressure washer to wash the underside of the bike? Or is there a more preferred method to clean Connie?

-x01660
 
I would NOT use a pressure wash device on the bike. Better to do it the old fashioned way, slower but much better for the bike.
 
x01660. Have you serviced the oil on the bike?
What your describing sounds a bit like an overfill.
Are you checking the oil level with the bike on the center stand about 10 minutes after running the engine?

Ride safe, Ted
 
connie_rider said:
x01660. Have you serviced the oil on the bike?
What your describing sounds a bit like an overfill.
Are you checking the oil level with the bike on the center stand about 10 minutes after running the engine?

Ride safe, Ted
Click to expand...

I changed the oil myself 2235 miles ago.

I don't have a center stand; or rather, I have it off the bike, as the PO took it off, and I cannot figure out how to tighten the bolt by the kickstand sensor; this bike apparently has lowering linkage in it, and I think its lowered it to the point where the bolt ends up right where the kickstand sensor is, so I can't get anything in there to tighten the bolt.

So I balanced the bike straight up and down while I changed the oil, and filled it until the oil was right under the top fill mark in the window.

I'm assuming that probably resulted in an overfill. I wouldn't be surprised if that was the case.

-x01660
 
As you did the fill 2200 miles ago, an overfill is not the cause.
(unless overfilling and then the bike laying on its side caused more oil than normal to flow into the airbox)

Try tying it down so that it sets level, run the engine until it warms up, then let it set for 5-10 minutes.
And then do your oil level check.

I'm like the others suspect oil in the air box.
1 other thought; Is the elbow securely attached to the bottom of the air box?

Ride safe, Ted
 
connie_rider said:
1 other thought; Is the elbow securely attached to the bottom of the air box?
Click to expand...

No, that's what I meant. The elbow is not attached. Its offset. I can see the nub on the end of the airbox where the elbow is supposed to cover.

I haven't had the time to put it back on. Will probably do that today.

But does THAT much oil come off of that elbow? The entire bottom side of my bike is coated, and I have a baking pan sized oil leak under my bike.

-x01660
 
Also, (don't wanna start a new thread), is it normal for the hex head bolts that hold the rear brake caliper on supposed to be really tight? I used a nub-ended Allen wrench with a breaker bar, and ended up snapping the nubbed end off the Allen wrench. I'm assuming that's not normal?

-x01660
 
Bolts are too tight or have Loc Tite on them.

Does THAT much oil come off of that elbow?

It shouldn't.
But you might have 2 (mebbe 3) things happening.
a) Accumulated oil coming out of the air box.
b) (if oil is overfilled) oil blowing out of the case.

Step 1: Take the cover off the side of the air box.
Remove/look at oil filter to see if it's oily and place a rag in the bottom of the airbox to see if there is a lot of oil inside.

Step 2: Correctly check the oil level in the tranny.

Step 3: Look under the water pump and see if oil is coming out of the small weep hole.

Ride safe, Ted
 
From your picture, that rubber elbow piece is suppose to connect to the air vent off the top of the engine (transmission section).

If it is not connected, then the blow by is just spraying out on the top and giving you the mess you are seeing.

In the air filter compartment, the air vent section is covered with a plastic piece that captures most of the oil in the blow by and allows it to drain down through the elbow back into the trans air vent. Any excess is drained out of the air filter compartment through the hose in the foreground of your picture to the left of the elbow.

Connect it up and see if it fixes it. I am looking at your 4th picture from the top.
 
I'll add two more..

LH side of the bike: the clutch push rod seal. They occasionally leak, especially if the rod has been removed and reinserted the wrong way. They have a VERY SLIGHT taper to them. and putting them back incorrectly will allow a loose fit with the seal. CAUTION: If you replace the seal, only insert it so the face of it is flush with the case boss. There's no stop for depth and you can push it in so they it can fall into the bowels of the bevel drive.

RH side of the bike: The balancer adjustment shaft seal. Rare, but I had one leak slightly on me a number of years ago.
 
Thank you all for the replies. I'll get my bike sorted.

But not today:

1.png


😫

-x01660
 
What? Perfect time to wash that area and have a rainwater rinse!
Seems to me you should clean the area to get the oil off, reconnect the elbow where it's supposed to go and ride it to see if the issue is resolved.
Combination of getting kicked over plus the elbow being off might just be it.
 
Jorge said:
What? Perfect time to wash that area and have a rainwater rinse!
Seems to me you should clean the area to get the oil off, reconnect the elbow where it's supposed to go and ride it to see if the issue is resolved.
Combination of getting kicked over plus the elbow being off might just be it.
Click to expand...

More about the temps, lol. And I don't have an enclosed area to work on my bike. And its parked outside. I have a cover on it to keep her dry, but yeah. Not trying to get sick...

That said, the rain will stop at 2am, so I'll definitely go out tomorrow, fix the bike, and clean everything up!

-x01660
 
Bumping this:

So I still have a steady drip of oil out of the bottom of the bike.

Its about 45F outside right now. I just went for a brief ride to the store. When I got back, I smelled a faint whiff of coolant around the seat. I took a look, and I saw (about 3 times) a quick white cloud of what I think is coolant, coming from where the alternator is. You know how if you spill some water on a hot stove, you get that quick evaporation? Like that.

Really hope it isn't the water pump.

What should I be checking for?

Mind you, I'm doing about 1000 mi/mo. I'm already at 2800 miles since my last oil change, a little under 2.5 months ago...

-x01660
 
Last edited:
If I remember right, there is a coolant pipe on back side of engine that has o-ring, or o-rings, sealing it to the side of the engine. These can leak slowly. May want to check them.
My C10 had a small coolant leak (I could smell it) that I couldn't find. I took my bike to Shoodaben for carb and cams and Steve found it and fixed it.
Seemed to not be horribly hard to fix.
Good luck!
On both leaks. :-(
 
On my C10, when I had the oil leak that was that bad, it was the bevel drive gasket that had gone bad, and it went all of a sudden.

2005 with ~ 44,000 miles when it happened ( 9 years after I bought it)
 
Check all your coolant hose clamps , might just need to tighten them up . Thermostat housing is in that area too and can sometimes leak at the base . If you haven't already , you really should change all the coolant hoses when you can .
 
x01660 said:
Bumping this:

So I still have a steady drip of oil out of the bottom of the bike.

Its about 45F outside right now. I just went for a brief ride to the store. When I got back, I smelled a faint whiff of coolant around the seat. I took a look, and I saw (about 3 times) a quick white cloud of what I think is coolant, coming from where the alternator is. You know how if you spill some water on a hot stove, you get that quick evaporation? Like that.

Really hope it isn't the water pump.

What should I be checking for?

Mind you, I'm doing about 1000 mi/mo. I'm already at 2800 miles since my last oil change, a little under 2.5 months ago...

-x01660
Click to expand...
I second what the others have said (check coolant hose clamps, condition of hoses, then look at the O-ring thermostat and "coolant log" joints). My ZX600-C has a similar cooling system design, and one of the O-rings in the cylinder jacket coolant log started leaking very slowly earlier this year. It wasn't enough to see dripping, because it didn't leak until the bike was warmed up and the cooling system under pressure, and at that point, it evaporated as fast as it leaked, but I could smell it. When I tore the bike down for some other work this winter, I looked closely and could see traces of dried coolant, so I pulled the log and found the O-rings to be flattened, hard, and cracked.

Murph has a handy pre-packaged kit with the correct O-rings for the coolant logs on the Concours.
 
If oil is seen dripping, the source may be higher up and not seen. Years ago Guy Young posted the trick of cleaning down the area and applying spray foot powder. The thin layer of white powder should show the oil leak path and helps identify the source point.
 
Looks like I'll be getting her up on the centerstand this Saturday....

If it is the o rings for the coolant logs and the bevel drive, how involved is it? I'm assuming a full coolant and oil change at a minimum; anything else I should be looking out for, or replace while I've got fairings off?

-x01660
 
Ok. I'm gonna bump this one more time.

Things have happened, and I REALLY am gonna need to depend on Voyager to do a LOT of work. Like, double what I've been doing. For the forseeable future. I need to get her up and running tip top.

Can someone please give me a list of all the gaskets/hoses/etc. I should replace in that area? I'll spend 2 days and whatever money needed to do it.

So far, I see that I should replace the gaskets/seals for the following:

  • Alternator
  • Bevel drive gear
  • Water pump
  • Oil logs/bars
  • Coolant hoses and clamps

Anything else I should be looking at to replace while I'm in there? I'm gonna order everything from Murph's tomorrow, so I wanna be comprehensive. I'll also be ordering stainless steel lines for the brakes and doing an oil change and replacing both tires. So I'd like to add whatever else I should be checking for/replacing for those parts as well.

Thank you all.

-x01660

Edit: If there's a COGer that's within 200 miles of Washington DC who would be willing to help with a day's work and has a workshop/place to work, I'll come out to you with parts, some beer, some cash, and unending gratitude. And I'll help. Work fast and hard. Need to get her tip top.

Thanks!
 
The bevel drive gear gasket is still available 11061-0157 at Ron ayers, not sure if Murph sells that. The old gasket was replaced with a metalized version, because a lot of bikes were losing this gasket and causing the oil leak. I could physically see the broken gasket working its way out of the top back on my drive unit.

It requires removing the tire, final drive,swing arm,drive shaft, clutch slave, and now you can remove the bevel drive itself. Took me a 1/2 day to do just that by itself. Re-assembled in about the same amount of time.

So if you can make sure it is leaking there before you have to tear into it.

I have never done the coolant logs, so don't have a good idea how long that would be.

Sorry that I can't help, I am in iowa (retired now).
 
Rear coolant log the carbs need to come out. Front ones the radiator and fan assembly needs to be tiped forward or removed. Protect your front fender if you just tip it. I think the manual says to remove the exhaust, but I did mine without removing exhaust. I did loosened the oil lines at the front of the engine. Clean up the engine ports for the logs to prevent leaks from new seal damage. Plan on new seals for the thermostat. They get gooey with age. The logs themselves are not that long to do, it's the time to get access to them,and cleaning the ports.
 
What do the rest of you use to lubricate the O-rings on coolant manifolds and pipes for installation? I've always just used some coolant, but it can be a bear to get them in. I'm tempted to use some silicone oil or silicone grease, but am not sure if that will contaminate the coolant.
 
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