Topic: Violent oil leakage from filter housing

[scbotanist]

Alright folks, I'm officially at a loss. 1973 CB500k2

Just got this bike, been nursing it back after it had been sitting for years. Wasn't running when I got it, but after a carb rebuild and new battery it was starting up.

I did an oil change to get it running smoother for a compression test and carb sync, but when I replaced the oil filter housing with a new filter, the housing exploded on me. I hadn't noticed some hairline cracks around the area where the filter bolt sat.

I got a new filter housing from a friend, but am having a similar issue. What happens is, I'll start the bike and after a few seconds, oil will get shot out of the side/bottom of the housing past the o-ring, and it'll keep leaking oil from there until I kill it. I thought that I had overfilled the oil, so I drained some and checked the dipstick, but that doesn't seem to be the case. I used the new aftermarket o-ring when I replaced the filter and I thought that may be bad, so I swapped back in the old o-ring but it's still doing the same thing. Honestly I'm at a complete loss at this point, and I'm getting pretty tired of wrenching that filter housing off and on only to have it burst another leak each time I start it up.

Any thoughts?

[ACK777]

Hello,

I was going to say that sometimes the new o-rings that come with those filters are not the exact dimension as OEM which could lead to leaks but it is strange that the old one is doing it as well (unless both of the o-rings are from new oil filter sets but I have never seen a bike literally hemorrhaging oil from around the oil filter housing).  Here is a link to the correctly sized o-rings for around the oil filter housing if you want to check the dimensions against the ones you have just to rule this out: https://www.oringsandmore.com/metric-buna-o-rings-89-x-4-5mm-minimum-2-pcs/

Does the bike leak oil onto the ground at all when it is just sitting and not running?

(If you end up needing a new o-ring that is the best website I could find stateside with reasonable shipping that does not charge you $13 to mail five $0.87 o-rings, 3 stamps, and a $0.01 envelope)

[HondaMan]

The O-rings in the filters today are for Suzukis and Kawasakis, and do not fit these bikes. Or more correctly, they are too thin for these bikes. The proper one is 4.5mm in diamter and seals the housing with just a light snug of the bolt.

You can get them from Honda ($4.50 each!) or sometimes (when in stock) at PartsNmore. They last forever: I am on my 3rd one at 140K+ miles. Your oil filter housing suffered the fate of being over-torqued by someone who was using the wrong O-ring. It will not seal, not matter what!

O-RING (89X4.5)
91316-425-003 (replaces 91316-300-003)

[newday777]

Did you save the washer and spring from the original filter?

[Don R]

 Are you sure the centering tab is lined up properly?

[BigJimG]

The O-rings in the filters today are for Suzukis and Kawasakis, and do not fit these bikes. Or more correctly, they are too thin for these bikes. The proper one is 4.5mm in diamter and seals the housing with just a light snug of the bolt.

You can get them from Honda ($4.50 each!) or sometimes (when in stock) at PartsNmore. They last forever: I am on my 3rd one at 140K+ miles. Your oil filter housing suffered the fate of being over-torqued by someone who was using the wrong O-ring. It will not seal, not matter what!

O-RING (89X4.5)
91316-425-003 (replaces 91316-300-003)

Well this was why I had such a PITA getting my oil filter housing to seal up this summer. on my '75F  I thought I was tightening it a LOT more than I should have to to get it to seal... Hopefully I didn't F anything up

[Alan F.]

Mark do you know about when (+/- ) they made that change in o-ring size? (big o-ring included with filters)

[scbotanist]

Hello,

I was going to say that sometimes the new o-rings that come with those filters are not the exact dimension as OEM which could lead to leaks but it is strange that the old one is doing it as well (unless both of the o-rings are from new oil filter sets but I have never seen a bike literally hemorrhaging oil from around the oil filter housing).  Here is a link to the correctly sized o-rings for around the oil filter housing if you want to check the dimensions against the ones you have just to rule this out: https://www.oringsandmore.com/metric-buna-o-rings-89-x-4-5mm-minimum-2-pcs/

Does the bike leak oil onto the ground at all when it is just sitting and not running?

(If you end up needing a new o-ring that is the best website I could find stateside with reasonable shipping that does not charge you $13 to mail five $0.87 o-rings, 3 stamps, and a $0.01 envelope)

The O-rings in the filters today are for Suzukis and Kawasakis, and do not fit these bikes. Or more correctly, they are too thin for these bikes. The proper one is 4.5mm in diamter and seals the housing with just a light snug of the bolt.

You can get them from Honda ($4.50 each!) or sometimes (when in stock) at PartsNmore. They last forever: I am on my 3rd one at 140K+ miles. Your oil filter housing suffered the fate of being over-torqued by someone who was using the wrong O-ring. It will not seal, not matter what!

O-RING (89X4.5)
91316-425-003 (replaces 91316-300-003)

Thank you sirs, I replaced the old o ring but it's possible that one wasn't OEM spec either since it came out of the cracked filter housing...I'll buy some OEM spec ones and give them a try.

Did you save the washer and spring from the original filter?

Hmm...that spring fits around the filter bolt and between the filter and the housing? I don't remember there being a spring with the old filter when I took it out...maybe that's the source of my woes. I'll try to find that part number and get a replacement.

[BenelliSEI]

And the washer. It’s usually missing, because it sticks to the filter and gets tossed.

[scbotanist]

And the washer. It’s usually missing, because it sticks to the filter and gets tossed.

I've got the old filter laying around so I've scavenged the washers, but the spring is nowhere to be found. Perhaps it ran off to a far corner of my garage floor...

[Don R]

 The spring keeps the filter against the crankcase so the oil goes through it. It may not have caused the violent leak however.  I have seen them assembled in reverse. A long time ago I took a backwards one apart and put it back like that.  Later I thought about it and when I checked I was amazed I didn't catch it the first time. 

[HondaMan]

You can get both the spring and washer at PartsNmore, usually. I install lots of the 'lost' washers in engines I get: they are frequently gone.

[seanbarney41]

the relief valve inside the big filter cover bolt is assembled wrong or totally clogged

[ekpent]

the relief valve inside the big filter cover bolt is assembled wrong or totally clogged

I was thinking the same thing. If I had any bolt I would be trying it out.

[scbotanist]

the relief valve inside the big filter cover bolt is assembled wrong or totally clogged

I was thinking the same thing. If I had any bolt I would be trying it out.

I assume you gents are referring to part #8 in the below diagram. Would cleaning it be as simple as removing the pin and spring (part #'s 9 and 10) and getting in there with some degreaser?

[HondaMan]

the relief valve inside the big filter cover bolt is assembled wrong or totally clogged

I was thinking the same thing. If I had any bolt I would be trying it out.

I assume you gents are referring to part #8 in the below diagram. Would cleaning it be as simple as removing the pin and spring (part #'s 9 and 10) and getting in there with some degreaser?

All this bypass valve does is to allow oil past it if the filter element is plugged. It doesn't raise, nor regulate, the oil pressure. When the pressure across this valve reaches about 7 PSI it opens and bypasses the oil straight from the pump into the main oil galley. This is parts #8 and #9 in this image from Honda's parts fiche.

[Little_Phil]

There were a lot of aftermarket bolts being sold with the 17mm head where the spring and internal parts of the relief valve were assembled incorrectly. Would that cause excess oil pressure with cold oil at start up.

[bryanj]

Nope, main pressure relief valve is on oil pump, only reason for valve in bolt is to bypass a blocked filter which,  if changed every 1500 miles, will not happen unless the engine is self destructing internaly

[Little_Phil]

Nope, main pressure relief valve is on oil pump, only reason for valve in bolt is to bypass a blocked filter which,  if changed every 1500 miles, will not happen unless the engine is self destructing internaly

Yea wasn't thinking...early Sunday morning. That restricts it at about 60 psi doesn't it?

[bryanj]

Thereabouts from memory, the manual gives you an exact figure

[tlbranth]

I use WIX 24940 oil filters on my cb and gl. They come with both o-rings and they work fine. You can get them online or at NAPA

[BenelliSEI]

So? Replaced the internal spring and washer? Correct “0” rings? Problem solved?

[HondaMan]

Mark do you know about when (+/- ) they made that change in o-ring size? (big o-ring included with filters)

The thicker O-rings were correct in the oil filter "kits" until around 2005 or so. Then they came with 2 thinner ones instead. The first ones I got that were 'wrong' came from EMGO.

[seanbarney41]

Mark do you know about when (+/- ) they made that change in o-ring size? (big o-ring included with filters)

The thicker O-rings were correct in the oil filter "kits" until around 2005 or so. Then they came with 2 thinner ones instead. The first ones I got that were 'wrong' came from EMGO.

that's weird...I use Emgo filters for years, because my local cycle shop always has a couple in stock when I am in a pinch and they never came with any o-rings.  I just order up a small stack o-rings from honda every now and then.

[scbotanist]

So? Replaced the internal spring and washer? Correct “0” rings? Problem solved?

Filter spring and washer came in the mail today. Threw them on with the correct O-ring, but the housing suffered the same failure on startup as every other time. On the bright side, I learned that my first cylinder isn’t firing (exhaust pipe was cold when the other three were warm), so I’ve got another issue to turn my attention to while I try to continue troubleshooting this!