Topic: CB500 Oil Leak

[JBCB500]

Howdy!

My CB500 has been throwing quite a bit of oil onto the back wheel (I know, super safe) during test rides.  I've had a look and there are a few drops on the surface of the oil pan, and what looks like minor leaks near the drain plug and at various points round the gasket.  None of these appear vary major though.

I was tightening down a bolt on my left side engine cover though, using what turned out to be too long a bolt, and I heard a popping sound, like I'd burst something.  It was the upper right bolt of the four, and when I removed it and the cover, oil flowed at a steady rate out of the bolt hole and onto the floor.  When I reinsert the (now correct sized) bolt, the flow of oil stops completely.  But after a run, I do notice oil coming from near where the left side cover meets the engine (no gasket here ofcourse).

I'll pull the oilpan soon and take a look but I assume I've burst into the engine housing or an oil passage?  If I can see the problem, I plan to fill in the hole with a bit of JB Weld but I wonder if anyone has any other advice?

Finally, has anyone routed the carb bowl overflow hoses to anywhere other than directly in front of the rear tire?  It just seems like a stupid place to be (potenially) dropping any fluids, however small the amount...

[DaveBarbier]

The hoses routed behind the engine and in front of the tire is fine. There isn't going to be (shouldn't be) much fuel at all. Don't worry about it. If you have more fuel coming out there time to see what's going on with the floats or overflow tube in the carbs.

Are you talking about the alternator cover or the sprocket cover? Sounds like you did "break on through to the otha side!!!" A couple clear pictures would help. If there's no bad case damage I wonder if you could use something like a thread sealer. Maybe Loctite 567 to seal the threads. There isn't going to be much pressure behind it. I wouldn't do a jb weld on the inside of the case. But since you said it's on the top of the cover there shouldn't be much oil at all coming out. There isn't an oil passage behind any of those bolts. Again, pictures would help.

It seems like you're thinking there's more than a couple leaks. Might just need a new oil pan gasket and drain plug crush washer. No biggie, if that's actually where it's coming from. But gravity might make a leak higher up seem like an oil pan leak. I'd pull the sprocket cover and take a look see. There's a handful of seals behind there that might be an issue. Something recommended here is cleaning the engine very well and dusting with baby powder. It'll tell you the source of the leak.

[flybox1]

Pictures would really help here.

[jkminer]

That sounds very similar to a leak my 500 was having.  I even had the rear lower bolt break through the case into the pan.  I just put a bit of RTV on the threads when I put it back together.  I just have to drain the oil if I remove the clutch cover now, no other issues with it.

I replaced the oil pan gasket, drain bolt, shifter seal and sprocket seal and was still leaking oil.  It ended up being the oil pressure switch in my case.  It ran down in just a way that made it look like it was coming from the pan or drain bolt.  After I replaced the oil pressure switch I went back to the usual drips and no more major oil leaks. 

[DaveBarbier]

That sounds very similar to a leak my 500 was having.  I even had the rear lower bolt break through the case into the pan.  I just put a bit of RTV on the threads when I put it back together.  I just have to drain the oil if I remove the clutch cover now, no other issues with it.

I replaced the oil pan gasket, drain bolt, shifter seal and sprocket seal and was still leaking oil.  It ended up being the oil pressure switch in my case.  It ran down in just a way that made it look like it was coming from the pan or drain bolt.  After I replaced the oil pressure switch I went back to the usual drips and no more major oil leaks.

Since the clutch cover has oil behind it what you could do is add a copper crush washer under the head of that screw. Using RTV, I'm sure, seals the leak too, but bits could come loose, especially when unscrewing and screwing it back in. Bits can easily clog the oil jets to the top end.

[jkminer]

I actually meant the left side engine cover had this issue, the one that covers the shifter, sprocket, clutch rod and oil pressure switch.

I like the idea of a copper crush washer, but not sure it would work with this bolt. When in areas as such I'm very careful with the rtv, just a tiny smear on the threads and none at the end of the bolt so there shouldn't be any to fall off into the pan.

[DaveBarbier]

I actually meant the left side engine cover had this issue, the one that covers the shifter, sprocket, clutch rod and oil pressure switch.

I like the idea of a copper crush washer, but not sure it would work with this bolt. When in areas as such I'm very careful with the rtv, just a tiny smear on the threads and none at the end of the bolt so there shouldn't be any to fall off into the pan.

Ah ok, yeah the crush washer wouldn't work there.

[JBCB500]

I'll get pics up tomorrow when I get a minute to pull it apart.  Thanks for the responses so far.

As for the drainplug crush washer - I did not replace this when I rebuilt the bike.  Anything special about this part or is this something I can find at O'reilly?

I did replace the sump/oilpan gasket.  I assume this is not the culprit.

[jkminer]

I had trouble finding one that was an exact fit at oreillys, you might get lucky.

How much oil are you losing, and is it only while the bike is running or does it continue to drip long after the bike stopped?

[DaveBarbier]

Any aluminum crush washer should work. Or copper for that matter. Hell, my 650 had a nylon washer and it wasn't showing signs of leaking. My Toyota pickup uses a fiber washer.

As long as it fits then you're good.

If the one you have is copper you could anneal it by heating it to red hot and dropping it in water.

[Duanob]

Does your crankcase vent tube vent directly to the ground? I know the 550 has a recirculating system.

[JBCB500]

Just picked up a couple of washers at Honda for 64 cents.

I haven't connected a hose to my crankcase breather.  Is this really essential?

FYI the bike has pods.

[JBCB500]

So I was typing from memory before.  In fact it was the longer, bottom right bolt and you can see from the attached pics what I've done.  In weld over the hole, jb weld the piece back on, or just locktite the bolt and put the cover back on???

I also discovered that the gasket for the oil pan was likely not sitting right as it appears to need stretched...

[flybox1]

Original HONDA gaskets (viton) wont shrink over time like that, FYI.
Get one that fits properly.  Think about it...if you have to stretch it, its OD will be less.   
Smaller OD = less material to compress and seal the pan. 

[jkminer]

That is exactly what mine did- down to the same bolt hole.

I just put a tiny bit of black RTV on the threads of the bolt (not at the end) and it didn't leak.  The only issue with leaving it like that is that if you need to pull that cover you'll have to drain the oil.

Oik leaks on 45+ year old bikes can be hard to track down.  When you have the left cover off check for any oil on the oil pressure switch with a paper towel or something, if there is any wet oil there, that might be your culprit.

[JBCB500]

Thanks gents.  Jkminer, I do have a bit of oil on my switch but not so much that it appears to be the source.  I will try the loctite method and between that and the gasket on the pan and the crush washer, I'm hoping for the best.

Flybox- excellent point!

[flybox1]

Id suggesting using a proper thread sealant, like ARP.
RVT can slough off and get lodged in your oil passageways. 
Not a good thing.  If you gotta use it, just use it sparingly.

[DaveBarbier]

Another option is using the thread sealant like I and Flybox said but putting it on a set screw (or grub screw) and threading it with an Allen wrench, then getting a shorter screw to hold on the cover (or cutting down the existing screw). That way you can remove the cover without oil leaking, plus removing the screw and reinstalling it often won't push the old cured thread sealant already in there into the motor. You're just holding on the sprocket cover, you can sacrifice a 1/4" of threads.

M6 1.0 is the diameter and thread pitch.

[JBCB500]

Great idea Dave!  I am quickly realizing how often I'll need the cover off and on so this will save me a fortune in oil!

[JBCB500]

I found out today (by running the bike with the left side cover off) that the leak was from the seal around the clutch rod.  Luckily I had a spare. I popped it in and no more leak. 

Weirdly though the battery is suddenly too weak to start the bike and I have to kick it over.  Also the oil light is on and the oil level is good.  If it were a modern car I'd suspect computer problems and disconnect/reconnect the battery.

Any idea why the oil light would suddenly be on?  I did diagnose the leak by allowing the bike to idle in the driveway for a while. Has this flattened the battery?

[calj737]

The oil light is a "pressure" warning light, not a level warning. 1 of 3 things is happening: either your oil pressure is bad (clogged oil sump screen or galleys, eroded pump rotor, etc) or the wire that serves it is losing its ground, or the switch itself has gone kaput.

Locate the switch (under that left side cover by the way) its a BLUE/RED striped wire. It should be connected to a small screw on the oil pressure switch. If it still is, remove the wire from the screw, key ON, and touch the wire end to the motor. Does the light go out? If so, pressure is fine, switch/wire is wonky.

I'd double-check the wiring since you just disrupted it by removing the cover and stuffing a new seal in there. In the attached picture, I have a brass set screw installed on top of the oil pump. Thats where yours is.

[DaveBarbier]

I did diagnose the leak by allowing the bike to idle in the driveway for a while. Has this flattened the battery?

That'll do it. These bikes only start charging at like 4k rpm or so. If you're going to be idling the bike for longer than a couple minutes, put a big box fan aimed at the headers. These things are air cooled remember. Your engine temps are going to go way up without it, eventually causing serious damage.

[JBCB500]

Thanks Cal.  I've been at the switch before actually.  Previously it wouldn't turn off and I inspected the wire as you suggest.  In doing so, I notice that the body of the switch itself was barely screwed into position.  I took a spanner and tightened it down and the light has been off ever since.  It does come on with the key in the ignition so I definitely didn't mess anything up.

This time though it is on all the time.  I'll re-check the wiring.  I did try and start the bike on the starter with the left side cover off and lent against the left side of the bike.  I can say for sure whether there wasn't contact between the wiring for the switch and the cover at some point but my understanding is that this wouldn't trigger the light permanently??

[calj737]

Thanks Cal.  I've been at the switch before actually.  Previously it wouldn't turn off and I inspected the wire as you suggest.  In doing so, I notice that the body of the switch itself was barely screwed into position.  I took a spanner and tightened it down and the light has been off ever since.  It does come on with the key in the ignition so I definitely didn't mess anything up.

This time though it is on all the time.  I'll re-check the wiring.  I did try and start the bike on the starter with the left side cover off and lent against the left side of the bike.  I can say for sure whether there wasn't contact between the wiring for the switch and the cover at some point but my understanding is that this wouldn't trigger the light permanently??

Correct, it would not. That wire is only a "ground" so you could not have likely hurt anything. Probably a loose connection is all. Or, you have a pressure problem?