Unusual oil leak from crankcase seal

[xanderick]

I've been going through all the respective Ninja 250 communities looking for people who have had this problem, and have seen nothing like this.



I saw a leak down around there, and wiped the engine spotless. Rode to work and found the leak spot, circled in green+red. So this spot is the source of the leak, no doubt about it.

Crankcase breather hose is not clogged, oil level is not too high. Crankcase has never been apart. Bolts are torque'd to spec.

The leak was very likely caused by gasoline getting into the crankcase (Thanks, n4mwd!), and I don't lose oil to the point where I need to add more, but it looks bad and I want to fix it. 2 options that I can think of: exterior application of silicone high-temp RTV sealant, or split the case and re-seal the whole thing. What's the process on dropping the lower half of the crankcase--or is that an extreme PITA?

[alex.s]

to split it you would need to drop the engine, drain all the fluids, remove about 30+ bolts along with the water pump, oil pump, clutch hub, starter, and various other little nice things. after that its a flat surface between the two bottomend halves that you would scrape clean and flat with a razor. and irregularity should be cleaned up with a fine sanding block and cleaned well. then hondabond the perimeter and reassemble.

i doubt putting some rtv on the outside will do anything.

the fact that its leaking makes you assume the case has been split before which makes you assume that it has had the tranny or bottom end or something replaced which is kinda scary i guess.

[xanderick]

Originally Posted by alex.s

to split it you would need to drop the engine, drain all the fluids, remove about 30+ bolts along with the water pump, oil pump, clutch hub, starter, and various other little nice things. after that its a flat surface between the two bottomend halves that you would scrape clean and flat with a razor. and irregularity should be cleaned up with a fine sanding block and cleaned well. then hondabond the perimeter and reassemble.

i doubt putting some rtv on the outside will do anything.

the fact that its leaking makes you assume the case has been split before which makes you assume that it has had the tranny or bottom end or something replaced which is kinda scary i guess.

Sounds like I'm going to leave it alone, then. I'm certain the case has never been split before, so that couldn't be the cause. No longer fond of Ninja 250s, for all these mechanical troubles I've been having...

[alex.s]

you are the original owner?

[xanderick]

No, but the original owners sold it to me with 5,000 miles. Had maintenance records and everything. The bike was super-clean at the time, no evidence of any tinkering of any sort, everything original.

So is it possible that the case has been split? Yes, it's possible, assuming the original owners lied to me. But really, really, really unlikely. I think we're much better off assuming that it hasn't been apart.

This leak started after I had the bike for 5 months and 10,000 miles.

[Monkeytofu]

you sure it's leaking from there? Maybe you just forgot to clean some road grime in that area. Trying cleaning that same exact spot again and seeing if it's actually leaking from that same.

No idea why anyone called these bikes bullet proof; they require a lot of maintenance but I think it's fun/worth it in the end.

[alex.s]

compared to many older engines these engines will take more than their fair share of a beating. i agree with monkey; to me it looks like splatter from the front wheel.

try tilting the bike toward that spot so you get oil up in there and see if you can get it to leak more

[xanderick]

Originally Posted by xanderick

So this spot is the source of the leak, no doubt about it.

Originally Posted by Monkeytofu

you sure it's leaking from there? Maybe you just forgot to clean some road grime in that area.

Originally Posted by alex.s

i agree with monkey; to me it looks like splatter from the front wheel.

Yes, I'm sure--"no doubt about it" means "no doubt about it". I have cleaned and checked this multiple times; the results are repeatable and consistent.

Originally Posted by alex.s

try tilting the bike toward that spot so you get oil up in there and see if you can get it to leak more

It only leaks when the bike is warm and running. And let's call it a "seep" rather than a leak. It's been doing this for 2 months and the oil still isn't low enough to require adding more.

[alex.s]

ok you seem very confident in your conclusions without stating really any concrete observations that lead to those conclusions. from what you have told us it might as well be a front brake fluid leak. if you can't replicate the leak in a "clean" environment (ie- bike holding still where you can watch it leak) then chances are something more is going on. why dont you warm the bike up to temperature then tilt it forward and to the right. if it doesn't leak with warm oil sitting on it then something else is going on.

and if it is really leaking so slowly that it only makes a few drops every month, who cares? just clean the few drops of oil up when you notice it.

[choneofakind]

I've got a similar "seep" out of the little twist cap that covers the place where you can put a ratchet on the crank and turn it for a valve adjustmet. I just wipe it once a season and call it a day. My

[alex.s]

Originally Posted by choneofakind

I've got a similar "seep" out of the little twist cap that covers the place where you can put a ratchet on the crank and turn it for a valve adjustmet. I just wipe it once a season and call it a day. My

theres supposed to be a rubber o ring that fits into those to stop that... its like $1 oem

[choneofakind]

Oh! Cool! Thanks alex. I'll look into that. Maybe I lost that.

[alex.s]

i only know this because i accidentally dropped it and put it back on without the oring and it leaked a little bit until i replaced the oring

[xanderick]

and if it is really leaking so slowly that it only makes a few drops every month, who cares? just clean the few drops of oil up when you notice it.

I'm fine with wiping it every once in a while, but I fear it would hurt the re-sale value of the bike to have a visible leak. If I were planning on keeping the bike forever, it really wouldn't be an issue.

[alex.s]

you might want to double check the torque on the bolts around that area just to be on the safe side

[xanderick]

Checked 'em once, will check them again. I would love for that to be the issue, but with my luck it probably isn't.

[n4mwd]

Another thing that can cause a leak between the two halves is gasoline in the oil. Sometimes the petcock fails and gas seeps into the oil through the carburetor. Gasoline can eat right through RTV. Might want to check that.

[CZroe]

I can think of one type of maintenance that may have required a opening the cases within 5,000 miles and wouldn't be in the regular service records: CRASH RESTORATION! If that happened then it may not even be the original engine... or 5,000-mile odometer for that matter.

[xanderick]

Originally Posted by n4mwd

Another thing that can cause a leak between the two halves is gasoline in the oil. Sometimes the petcock fails and gas seeps into the oil through the carburetor. Gasoline can eat right through RTV. Might want to check that.

We have a winner! Gas getting into the oil has been a recurring issue for both ninjas I've owned. I've solved that issue, but the gas was there and the damage done, apparently. I had my suspicions, but didn't realize the gas would eat through the stuff so quickly.

For my last bike, it was the petcock--it actually messed with the cam chain tensioner and caused a cam chain failure at only 2500 miles. I was not mechanically inclined at the time, so I never knew what killed the bike until it was too late. The petcock on my current 07 Ninja is fine, but the float valves were sticking open. I fixed that quickly and changed my oil. Not soon enough for the crankcase seal, obviously...

Still no way to stop the leak now that it's started, unless I pull the engine and go through splitting and re-sealing the crankcase.

[n4mwd]

Originally Posted by CZroe

I can think of one type of maintenance that may have required a opening the cases within 5,000 miles and wouldn't be in the regular service records: CRASH RESTORATION! If that happened then it may not even be the original engine... or 5,000 odometer for that matter.

Here is one way to check to see if the engine is the right year for the bike. Its a list of engine serial numbers cross referenced by year.

1986 EX250EE000001
1987 EX250EE008???
1988 EX250EE015170
1989 EX250EE053???
1990 EX250EE058???
1991 EX250EE073???
1992 EX250EE088???
1993 EX250EE101???
1994 EX250EE118???
1995 EX250EE127???
1996 EX250EE137???
1997 EX250EE149???
1998 EX250EE151???
1999 EX250EE158???
2000 EX250EE16????
2001 EX250EE167???
2002 EX250EE170???
2003 EX250EE18????
2004 EX250EEA00001 Start of assembly in Thailand
2005 EX250EEA084??
2006 EX250EEA16???
2007 EX250EEA29???

[n4mwd]

Originally Posted by xanderick

We have a winner! Gas getting into the oil has been a recurring issue for both ninjas I've owned. I've solved that issue, but the gas was there and the damage done, apparently. I had my suspicions, but didn't realize the gas would eat through the stuff so quickly.

For my last bike, it was the petcock--it actually messed with the cam chain tensioner and caused a cam chain failure at only 2500 miles. I was not mechanically inclined at the time, so I never knew what killed the bike until it was too late. The petcock on my current 07 Ninja is fine, but the float valves were sticking open. I fixed that quickly and changed my oil. Not soon enough for the crankcase seal, obviously...

Still no way to stop the leak now that it's started, unless I pull the engine and go through splitting and re-sealing the crankcase.

Unless it gets really bad, I would just wipe it and go. Fix it next time you have to split the case for other reasons.

[xanderick]

Originally Posted by n4mwd

Fix it next time you have to split the case for other reasons.

Heh, hopefully I can just keep wiping it for the forseeable future. Not eager to pull the engine apart any time soon, that's for certain.

[xanderick]

Also, the carb overflow tube is pretty useless. Other bikes I've had would leak gas out of the overflow tube when the float valves stuck. Never on my Ninja 250. I played with the hose routing, checked for blockages and everything. Seems like maybe it's a Kawi/Keihin design flaw.

[n4mwd]

Originally Posted by xanderick

Heh, hopefully I can just keep wiping it for the forseeable future. Not eager to pull the engine apart any time soon, that's for certain.

Its not too bad to separate it. You'll need to get new side cover gaskets. The heads do not have to be removed so no need for gaskets there. The seal between the halves is made with HondaBond HT. I've heard of people using regular RTV and having trouble with leaks so if you do it, use HondaBond HT. The worst part of the process is making an engine stand that can hold it while you work on it.

You might think about it if you have any long down time.

[xanderick]

I may do that. I'd like to do it just to have the experience, honestly. Only issue is I can't afford any downtime for the bike. It's my only vehicle.

There's a DIY motorcycle shop I go to, might be able to knock the project out over a weekend. Otherwise I'll let it seep.

[n4mwd]

Originally Posted by xanderick

I may do that. I'd like to do it just to have the experience, honestly. Only issue is I can't afford any downtime for the bike. It's my only vehicle.

There's a DIY motorcycle shop I go to, might be able to knock the project out over a weekend. Otherwise I'll let it seep.

If you are already experienced in motorcycle repair, then possibly a weekend with the proper tools. Also, if you have someone who has already split one, it will help.

Its basically three steps. 1) Drain all the fluids and get it off the bike. 2) split the engine and reseal it. 3) Reinstall the engine.

There are a lot of time killers like cleaning the gasket faces and waiting for the gasket remover stuff to dissolve them. Then repainting the paint that they accidentally eat off.

Anyhow, if you get like a week off, I would think that is reasonable to get it done provided you already have all the gaskets and HondaBond HT. Don't count on dealers to stock the parts you might need. They never do seems like.

[CZroe]

Damn. My bike's petcock does leak and my oil always smells of gas. I believe I've got the same defect many of our Ninjette's have with the incomplete teflon ring.

[KELPHYN]

Blah-blah-blah. . . Take a bar of soap (sunlight laundry bar) rub it back and forth along the seam. Wipe off any large chunks with your finger. Go ride your bike.

[xanderick]

Originally Posted by CZroe

Damn. My bike's petcock does leak and my oil always smells of gas. I believe I've got the same defect many of our Ninjette's have with the incomplete teflon ring.

If the oil smells of gas, change it. Of course, it's good to keep more gas from getting in there or you'll still have problems.
Also check gas level in carbs in case it's your float valves/height/etc. Maybe you know the procedure to that, maybe not--but here's an illustrated guide I made a few months back. Explains way better than words alone:


note: I originally made this for a friend, the bit about the CB400t refers to an old Honda he and I had worked on prior to looking at my Ninja 250

[n4mwd]

I also need to point out that if you have gas in the oil, then the oil is pretty much useless and not lubricating the engine. So you shouldn't ride it like that if you like your bearings - especially at higher RPM's. If you mess up your bearings, you wont have a choice about splitting the case.

[CZroe]

Originally Posted by xanderick

If the oil smells of gas, change it. Of course, it's good to keep more gas from getting in there or you'll still have problems.
Also check gas level in carbs in case it's your float valves/height/etc. Maybe you know the procedure to that, maybe not--but here's an illustrated guide I made a few months back. Explains way better than words alone:


note: I originally made this for a friend, the bit about the CB400t refers to an old Honda he and I had worked on prior to looking at my Ninja 250

Thanks!

Originally Posted by n4mwd

I also need to point out that if you have gas in the oil, then the oil is pretty much useless and not lubricating the engine. So you shouldn't ride it like that if you like your bearings - especially at higher RPM's. If you mess up your bearings, you wont have a choice about splitting the case.

Thanks. The bike's been ridden 35K miles and it was likely polluting it all along or for at least the last 15K. I skipped an oil change when I switched to Rotella T6 but noticed that it darkened notably in the first day or two. I didn't know it smelled like gas until I changed it after skipping a change like full synthetic oil proponents often suggest. Once again, it blackened very quickly. I changed it again only days later as part of a valve job with Casey and it smelled strongly of gas again. That's also when we noticed that my tank petcock was leaking. Also, my cam chain was making a loud noise (still is) that would go away when resetting the CCT but come back after a full cycle (warm, cool, fresh start). I have no warranty, of course, but I'd still like to report the petcock issues in hopes of generating a recall. I have seen many members here mention the exact same petcock problem. Who do I report to? The NTSB? Not sure that it's a safety issue.

[alex.s]

how does the gas get into the oil? leaks into the cylinder then gets around the rings and skirt?

[CZroe]

Originally Posted by alex.s

how does the gas get into the oil? leaks into the cylinder then gets around the rings and skirt?

I dunno, but this is at least the second time I've heard a statement like this:

Originally Posted by n4mwd

Another thing that can cause a leak between the two halves is gasoline in the oil. Sometimes the petcock fails and gas seeps into the oil through the carburetor. Gasoline can eat right through RTV. Might want to check that.

[alex.s]

leaks down the intake right? shouldn't the rings and oil skirt keep it in the cylinder for at least a little while? i mean if it was leaking a lot you would seriously damage the engine when you went to start it? (think hydrolock but with an explosion) so it would have to be a very slow leak over a long time huh? but if it gets ridden every day i would think that small leak would get burned up before it really had a chance to get anywhere. unless it was just sitting for a long time (right before the PO sold it?) it makes sense for where its leaking... the gas would drip down the intake into the cylinder then to the ex. side of the cylinder and down the sides of the case and would pass right over that area as it makes its way down into the bottom of the case...

[CZroe]

Originally Posted by alex.s

leaks down the intake right? shouldn't the rings and oil skirt keep it in the cylinder for at least a little while? i mean if it was leaking a lot you would seriously damage the engine when you went to start it? (think hydrolock but with an explosion) so it would have to be a very slow leak over a long time huh? but if it gets ridden every day i would think that small leak would get burned up before it really had a chance to get anywhere. unless it was just sitting for a long time (right before the PO sold it?) it makes sense for where its leaking... the gas would drip down the intake into the cylinder then to the ex. side of the cylinder and down the sides of the case and would pass right over that area as it makes its way down into the bottom of the case...

I was riding every day so it probably was a slow leak over a long time contaminating the oil but it has hardly been ridden at all in the last year. I keep starting it up about once a month to warm it up and keep the carbs clear (the gas is stabilized) but I may be doing serious damage if there has been significant leakage since my oil change last December despite putting on near zero miles.

Good thing I have a backup Ninjette, but I really am concerned about this possibility. It does seem to explain the funny-smelling oil and I don't think it's coincidence that my petcock leaks and my cam chain is probably in need of replacement. Also, I went about two months between warmups this last time and started it for a few minutes on Saturday but could not on Sunday. I changed the plugs and it fired up but the old plugs were soaked in gas, as I reported in the "what did you do today" thread.

[alex.s]

ruh roh

[xanderick]

Originally Posted by alex.s

leaks down the intake right? shouldn't the rings and oil skirt keep it in the cylinder for at least a little while? i mean if it was leaking a lot you would seriously damage the engine when you went to start it? (think hydrolock but with an explosion) so it would have to be a very slow leak over a long time huh? but if it gets ridden every day i would think that small leak would get burned up before it really had a chance to get anywhere. unless it was just sitting for a long time (right before the PO sold it?) it makes sense for where its leaking... the gas would drip down the intake into the cylinder then to the ex. side of the cylinder and down the sides of the case and would pass right over that area as it makes its way down into the bottom of the case...

I've had mine do it to me sitting only overnight, more than once. My guess is the rings aren't designed to have gasoline just chilling in a puddle on top of them, and the stuff seeps through pretty quickly. I finally had the oil smelling like oil when I was prepping for a cross-country roadtrip, and it started smelling like gas before I hit California just from it sitting overnight each day of the trip.

The "fuel in the oil" gremlin really pisses me off. And once you get gasoline in the oil, the oil filler cap will smell of gas even after the next oil change--at which point you can never be sure how much gas is or is not in the oil. I've been really paranoid about it these days, so I run the carb bowls dry before I shut the bike off every single time, no matter how long I plan on parking.

[CZroe]

Originally Posted by xanderick

I've had mine do it to me sitting only overnight, more than once. My guess is the rings aren't designed to have gasoline just chilling in a puddle on top of them, and the stuff seeps through pretty quickly. I finally had the oil smelling like oil when I was prepping for a cross-country roadtrip, and it started smelling like gas before I hit California just from it sitting overnight each day of the trip.

The "fuel in the oil" gremlin really pisses me off. And once you get gasoline in the oil, the oil filler cap will smell of gas even after the next oil change--at which point you can never be sure how much gas is or is not in the oil. I've been really paranoid about it these days, so I run the carb bowls dry before I shut the bike off every single time, no matter how long I plan on parking.

No handle on the petcock for my bike.

[alex.s]

i might be confusing my fzr carb boots with the ninja but i think there is a hole with a screw in it on the bottom of the carb boot that you can unscrew and thread in a welders tip, then put a little hose on the tip and lead it down to a bucket with a paper towel... if the carbs are leaking, the gas will flow down the intake boots and some gas will come down the tube and fall into the bucket... it will evaporate the next day but you'll see a stain in the paper towel from the gas that leaked, if it leaked.

you could also try removing the carbs and setting them in a bucket or something and see if they leak off the bike

[n4mwd]

Originally Posted by alex.s

how does the gas get into the oil? leaks into the cylinder then gets around the rings and skirt?

The carb bowls overflow and the gas runs into the intake and into the engine. The piston rings aren't solid and have a split. The gas seeps into the crankcase through those splits.