Topic: The leak returns! I will not be beaten! K4 in Distress....

[Ujeni]

Here's the story...

A few months ago, I had low compression and a leak between the cylinder and the head. I had the cylinder and the head surfaces milled down professionally, installed heavy duty studs, honed the cylinders and used a MLS head gasket from CycleX. All of this resulted in near-perfect compression and better power. You can read the story here:

http://forums.sohc4.net/index.php?topic=116218.0

After a few test rides, the leak came back (though there is much less...I would call it an oil weep myself) 

Here's a pic (note that it is on the cylinder fins and the head fin):


It appears to be spraying back on the left side cover too:


There is a bit on the right side too:


Argg!! Why is it still there?

Upon some reflection and a bit of research, I think I have a candidiate: I think I might have a 71 cylinders while the rest of my engine is from 74. My research shows that the 74 has 8 dowel pins that go in the top of the cylinder block. I ordered those parts, but they wouldn't fit in my cylinder block.

Here's a 71 cylinder schematic:


and here's a 74 cylinder schematic:


I think I have the 71 cylinder head and thus no dowel pins. Could this be the cause of the leak? If so, should I search for a 74 cylinder block? If this can't be the cause, what should I look for?

[MCRider]

Much discussion here about the with and without  8 ORing setups. Bottom line Honda did it to reduce oil seepage, but a well built example without them should not leak. They can be left out without leakage.

The fact that the oil is ABOVE the headgasket eliminates the ORing issue, and headgasket. Above the headgasket leaks come from the 6 rubber buttons and/or the four stud holes where the hold down studs for the front of the cam bearings go. Have those studs ever been removed? If so they need to be relaced with sealer.

Been there.

I'd pull the top off, service those studs (if they've been removed from the stock install), retorque the head nuts (worked for me twice) and retry.

[Ujeni]

Hmmm, I like the sound of this.

I can't picture the hold-down studs you are talking about. I do know the six rubber buttons though. I used the old ones...that seems like a good place to start. Can you tell me more about the studs? How would oil leak through there if the studs are in place?

[Xnavylfr]

What about the rubber caps UNDER the cam towers??


Xnavylfr(CHUCK)

[MCRider]

What about the rubber caps UNDER the cam towers??


Xnavylfr(CHUCK)

That's what we're talking about.

[phil71]

http://4into1.com/vesrah-sealing-rubber-ab-1001-honda-cb500-cb550-cb650-cb750/


those pucks are usually too stiff to be reused.

[MCRider]

Hmmm, I like the sound of this.

I can't picture the hold-down studs you are talking about. I do know the six rubber buttons though. I used the old ones...that seems like a good place to start. Can you tell me more about the studs? How would oil leak through there if the studs are in place?

Yeah, used ones are a no-no. Gotta suspect them. Should be new with some non-hardening goo like Gasgacinch.

The studs are 4 6mm studs coming out of the top of the head. The cam bearings drop on top of them and the caps are nutted down on them. The caps are held by those stud/nuts and 4 bolts across the rear.

The studs are threaded into the head at the factory. The holes they are threaded into are threaded all the way thru the head and exit above each sparkplug. IF the original factory seal is disturbed, ie the studs are removed, they should be reinstalled using a thread sealer. Sometimes they are removed for cleaning or porting purposes. Bolts are then used instead of the studs. Another no-no. Any chance for oil to wick down those thread holes will drip oil onto the 3rd (or 4th) fin of the head, which will then drip lower and lower. Same for the rubber duckies.

[Ujeni]

Gotcha. I see them in the schematics now (and I remember them).

Knowing that the studs are still there, how do I know if I should remove and reinstall them with thread sealer?

[MCRider]

Gotcha. I see them in the schematics now (and I remember them).

Knowing that the studs are still there, how do I know if I should remove and reinstall them with thread sealer?

IF they've never been removed, don't touch them. I've never seen a factory install leak. IF that is the leak you can look in the #1 or #4 spark plug cavity in the fins and see where that hole opens to the atmosphere and you'd see the oil dripping. To see #2 ands #3 you've got to look in with a flashlight thru the fins at the side of the motor across to where those holes are. On mine you could see the oil RUNNING out of the holes.

I've read here someone cleaned and JBwelded the hole shut and fixed the leak. Mine was terminal. New (used) head. I had stripped the holes and rethreaded them. Terminal leaks, except the JBWeld trick may have worked had I thought of it.

Yours is probably the used oil puckies.

[Ujeni]

Ok, I've ordered the rubber pucks and a head valve cover gasket. I'll pull the engine this weekend to inspect.

Thanks for your help! I'll report back when I have some findings.

[Ujeni]

Hmmmm, I took a closer look at the leak and now I am not sure it could be the result of the bad rubber pucks. The oil trail appears to start on the second fin from the top of the cylinder block. Here's a pic of the side of cyl 4:



There is oil on the head as well, but I can't see any in the area of the spark plugs.

What do you think, are the rubber pucks still my best bet or is there another possibility?

[Harsh]

Search for Honda Service Bulletin 42.  It might help you with getting the correct o-rings.  The last I knew the only place that had any was Western Hills Honda.

[MCRider]

I lose track with all the back and forth. Bottom line: oil starting above the head gasket, on the head fins, is pucks or stud holes. Oil at the head gasket level or lower is the head gasket and/or o Rings. (Or oil dripping down from above. Look to the leading edges of the head fins. They get drips on them which blow back lower onto the cyls once under way.)

For the oil on your head fins, I suspect the pucks.

For the oil on your cylinders, it could be dripping down from above, or, a retorque of the head nuts may cure that.

Diagnostic trick. Clean everything really well. Powder the areas with baby powder and watch for the oil to appear.

[Ujeni]

Went through the engine. Could not find any oil below the pucks or the studs. I did find that all cylinder head nuts were under-torqued. I re-torqued them, triple checked and put the bike back together.

I'll begin the test period tomorrow. Hoping that the leak was the result of under-torqued cylinder head nuts!

[74750k4]

Having a similar issue as you. Using MLS Cometic Gasket. No leaks before about 150 miles or so, suddenly leaks started. Now at 1000 miles. Oil appears at front of the side fins of cylinders starting at gasket area, and down. Stuffed rolled up paper towel in there at gasket fins. So far that has stopped any evidence of oil. I used stud orings/dowels. Maybe should not have. Checked torque on the spark plug accessible head nut. Still has 22 ft. pounds on HD studs. Kinda wondering if the (2) longer #11 alignment dowels might be too long, and preventing a good seal in that area. At any rate looks like I'll be pulling the engine again too. PITA!

[lucky]

Having a similar issue as you. Using MLS Cometic Gasket. No leaks before about 150 miles or so, suddenly leaks started. Now at 1000 miles. Oil appears at front of the side fins of cylinders starting at gasket area, and down. Stuffed rolled up paper towel in there at gasket fins. So far that has stopped any evidence of oil. I used stud orings/dowels. Maybe should not have. Checked torque on the spark plug accessible head nut. Still has 22 ft. pounds on HD studs. Kinda wondering if the (2) longer #11 alignment dowels might be too long, and preventing a good seal in that area. At any rate looks like I'll be pulling the engine again too. PITA!

Always check dowel pin heights!!!

[Ujeni]

Fired the engine up. Sounded good.

After a few minutes, I looked down and saw what I thought was a tiny weep of oil at the headgasket. To be sure. I cleaned the area and put some flour on it to try to trace the leak. Sure enough, after a few minutes of riding, this appeared:



 

Guess I need to take the engine out again and dive deeper. I am super surprised that the MLS gasket appears to be leaking. I thought that was my ticket to fixing this problem. Anyone have any more ideas?

[74750k4]

2nd MLS gasket is on the way from CycleX... So far, the paper towel roll on both sides is keeping everything clean. 250+ miles using that. The locating/alignment dowels are stock sized, so just the depths into the head/cylinder need to be carefully measured for dowel protrusion/interference. As far as I can tell from your photo, we have the exact same issue.

[Ujeni]

I looked further into the dowels. Turns out that the eight dowels were introduced in mid 1974 on engine numbers 2352923 and afterwards. Mine is starts with 2340...so My problem is not lack of dowel pins (of course the normal two dowel pins still apply).

I guess I'll order a new MLS gasket after I get into the engine.

First one to figure out the problem wins!