Author Topic: F2 head with K Cylinders, leaking oil all around the head. (Read 9981 times)

scondon · « **Reply #25 on:** March 02, 2011, 03:37:45 PM »

Quote from: Terry in Australia on March 02, 2011, 02:17:03 PM

Quote from: scondon on March 02, 2011, 11:05:19 AM
Quote from: Terry in Australia on March 02, 2011, 02:49:57 AM
Er, just so you know, you can't actually use a K cylinder block with an F2 head. Or it'll leak oil and burn your leg. Cheers, Terry.

Bugger all to hell, the Aussie is right

In the K models, and F0/F1 bikes, all 8 (inner and outer) oil returns are utilized. On the F2 model the inner four returns are not used(the ones capped with copper washers). These are plugged at top with the copper washers, and at the bottom of cylinder block(different casting of F2 cylinder block, and rubber seal).

If you look with a flashlight through the fins of your F2 head(just outside the 2-3 exhaust ports) you will see your heavy duty cylinder studs peeking out. These returns are venting to atmosphere, and oil is backing up the bottom of your K block and pouring out of them. Crap!

"Everything I read and what Ken at Cycle-X said it shouldn't be an issue, but I am running a F2 head on top of K cylinders with an F2 836 kit." If Ken Sold the pistons and block as a kit for you then hopefully he can help with the fix.

Thanks Sean, as you'll recall, it was our crazy English mate Karl (KaceyF2) who told me back in 2005............

Apparently things work opposite in the Southern Hemisphere, Terry. All that bourbon has erased my memory while it seems to have enhanced yours. Can't believe it only took a couple years absence to make me forget everything I ever knew on this subject

Mandic, here is a link from an old post that has a photo of the bottom of the F2 cylinder block. This is the block that is needed if you want to use that F2 head of yours. It's from a thread where I was doing the opposite as you, using a K head on an F2 block.

http://forums.sohc4.net/index.php?topic=17622.0

On the K block that whole area is opened up to allow all 8 oil returns from the head to drain. What is happening to you is that the oil is draining from your F2 head "down" the outer 4 drains, and seeping back "up" the inner 4. On the K heads these inner four are NOT open to atmosphere, only the F2 head is this way. Oil will seep out the two front, and two rear inner stud holes. If you wash your bike or ride in the rain water will wash down these and into your crankcase.

All this was written in quite detail and posted in our FAQ a while back. I'll see if I can find it.

EDIT: The information was edited a bit and no longer contains this specific of F2 compatibility. However there still is some info on the subject about 4 posts down in the FAQ

http://forums.sohc4.net/index.php?topic=369.0

Mandic · « **Reply #26 on:** March 02, 2011, 03:47:52 PM »

The picture didn't come through. I understand what you are saying but not why it would go to the outside. I cannot see this spot you mention where the studs are open to the air. All I see when I look between 2/3 is the tops of the shorty studs. And this entire area is bone dry of oil.

The leaks SEEMS to be all around the head gasket. To the point that when I let it get hot just now and bumped the idle up a ways, I could see bubbles forming at many points around the head gasket. It would seem that the head isn't seated down well enough. Maybe those knock pins and seals are not letting it sit down.

Ken mentioned this problem as did a few others here. I'm thinking I need to pop the head off to find it. I mean if the entire head surface is damp with oil, then that is fairly obvious. I'm going to let it sit and drain a bit before I pull it apart so less is sitting in the head.

MCRider · « **Reply #27 on:** March 02, 2011, 03:51:05 PM »

Quote from: TwoTired on March 02, 2011, 01:50:30 PM

Quote from: MCRider on March 02, 2011, 11:42:45 AM
wITH a 360degree crank you have the same pressure whether the rings are seated or not, seems to me. Same amount of volume is opening up with 2 pistons rising as is being compressed with 2 pistons falling. Seems to me. Basically.

Agree, IF there is no combustion blow by the piston rings. (You probably mean rod journals at 180 degree crank positions, too.)

Cheers,

Yes, I mispoke. Ours would be a 180° crank. Thank you.

TwoTired · « **Reply #28 on:** March 02, 2011, 04:04:42 PM »

Does the 750 have o rings for the oil passageways like the 550? If those were left out/damaged, it would certainly look like a head gasket leak. And it would be worse with higher oil pressures.
I dunno. Just a thought.

Cheers,

Mandic · « **Reply #29 on:** March 02, 2011, 04:08:54 PM »

You mean at the base and top of the gasket surfaces on the "feed" studs? Yes it does. And they were in there. Whether they became damaged, that I don't know. I'm going to go get dinner and let the bike cool down before I attempt disassembly. Hopefully yet tonight I will have pictures of what I find. And hopefully with just the head off and not the cylinders too.

scondon · « **Reply #30 on:** March 02, 2011, 04:20:35 PM »

Quote from: Mandic on March 02, 2011, 03:47:52 PM

The picture didn't come through. I understand what you are saying but not why it would go to the outside. I cannot see this spot you mention where the studs are open to the air. All I see when I look between 2/3 is the tops of the shorty studs. And this entire area is bone dry of oil.

The leaks SEEMS to be all around the head gasket. To the point that when I let it get hot just now and bumped the idle up a ways, I could see bubbles forming at many points around the head gasket. It would seem that the head isn't seated down well enough. Maybe those knock pins and seals are not letting it sit down.

Ken mentioned this problem as did a few others here. I'm thinking I need to pop the head off to find it. I mean if the entire head surface is damp with oil, then that is fairly obvious. I'm going to let it sit and drain a bit before I pull it apart so less is sitting in the head.

I forgot to put the link to the photo in the post. It's there now. Terry and I are remembering this compatibility issue that was little known and hard fought by poor Karl to get anyone to believe him, even to the point that Terry built his motor anyway and it seeped oil out on him too. It may not be the issue you are dealing with directly at this moment, but you should be aware of it in case you are pulling your motor apart.

I don't have a camera so I'll try and describe it with a little analogy. You have two sinks side by side, and their two drains connect underneath in a "Y" junction to a single pipe. You cut the wall between the sinks and join them together to make one big sink. No longer do you need both drains so you plug the sink on the left, and disconnect the pipe underneath it.

You are now only draining from the right side of the "Y" junction, and the left side of the "Y" is open to atmosphere. There is no problem with overflow until something restricts the flow from the bottom of the "Y" and then water comes pouring out of the open left side.

scondon · « **Reply #31 on:** March 02, 2011, 04:40:34 PM »

Do a search for Kaceyf2. Also go to the FAQ and scroll down to the greenspun archives link and do the same search there. You will be able to find lots of discussion in his posts on this subject, including the one where Terry denies there is any problem haha.

Here's one where Carl describes and compares the drains on the K vs. F2.

http://archives.sohc4.net/index.php?topic=11771.msg54892#msg54892

MidnightLamp · « **Reply #32 on:** March 02, 2011, 04:40:51 PM »

If it helps, I have: an F2 (head, cylinders, cases) and a K5 (head, cylinders, cases) apart on my floor right now. Shall I snap some comparative photos?

Mandic · « **Reply #33 on:** March 02, 2011, 04:48:15 PM »

Please do, it cannot hurt to add some more images for everyones minds to mull over.

I understand what is being said about the oil "leaking up" or whatever you want to call it. But I don't really see it as my issue. I thought I checked those holes to see if they were open to atmosphere. I may be wrong though. I will pop my head off and check. No matter what the issue it sounds like that has to happen.

scondon · « **Reply #34 on:** March 02, 2011, 04:57:33 PM »

Quote from: Mandic on March 02, 2011, 04:48:15 PM

Please do, it cannot hurt to add some more images for everyones minds to mull over.

I understand what is being said about the oil "leaking up" or whatever you want to call it. But I don't really see it as my issue. I thought I checked those holes to see if they were open to atmosphere. I may be wrong though. I will pop my head off and check. No matter what the issue it sounds like that has to happen.

Sorry to have hijacked your thread with this, Mandic. Having had to pull a few engines myself I just didn't want you to pull yours apart for another issue, fix that, and have it STILL leak oil.

MidnightLamp · « **Reply #35 on:** March 02, 2011, 06:38:44 PM »

Comparison Pics:

K5 Cylinder bottom:

F2 Cylinder bottom:

Mandic · « **Reply #36 on:** March 02, 2011, 07:26:33 PM »

Quote from: scondon on March 02, 2011, 04:57:33 PM

Quote from: Mandic on March 02, 2011, 04:48:15 PM
Please do, it cannot hurt to add some more images for everyones minds to mull over.

I understand what is being said about the oil "leaking up" or whatever you want to call it. But I don't really see it as my issue. I thought I checked those holes to see if they were open to atmosphere. I may be wrong though. I will pop my head off and check. No matter what the issue it sounds like that has to happen.

Sorry to have hijacked your thread with this, Mandic. Having had to pull a few engines myself I just didn't want you to pull yours apart for another issue, fix that, and have it STILL leak oil.

It is fine by me. THat was my goal, to compile the information I needed here. If what you say is the case then yes, I am screwed more so than I thought, ha. And it is important to be aware of that before I slap it back together again.

Mandic · « **Reply #37 on:** March 02, 2011, 10:46:49 PM »

Welp, now that I have the exhaust off I can see one of the points you guys were making. Between the 3/4 and 1/2 exhaust ports I can see the heavy duty engine studs. Thinking back, these were the studs that were rusty and decrepate upon disassembly. Because they ARE open to atmosphere. So a K cylinder WILL allow water down in there, and oil up out of there.

Is this my issue? I don't necessarily think so, but it is not going to work. Won't be too long until I have the head off.

Mandic · « **Reply #38 on:** March 03, 2011, 12:04:42 AM »

PROBLEM FOUND: Well after disassembly I found my problem. The "knock pins" for the oil return studs, are sticking up above deck height approximately .040. This didn't allow the head gasket to properly squish and seal. So that was why my head appeared to leak oil from everywhere, it was. I'm amazed I wasn't hazing out the exhaust more then. The combustion chambers show evidence of the oil being in there.

F2 Head on K Cylinders: NO GO. I will post pictures in the morning, but you guys are completely correct. There was oil around the return ports that are "unused" with the F2 head. So oil WAS pushing up those return lines and forcing out passed the cylinder studs. I need an F2 cylinder.

I am going to contact Cycle-X asap tomorrow and see if they have my F2 cylinder I sent in for a core and figure things out. If not I will be getting a hold of someone here to get one. I want to run F2 parts. I sunk money into this better flowing head and my 836 pistons are the F2 kit pistons.

I will post pictures tomorrow showing clearly why the F2 cylinder head on K cylinder is a NO GO. Sorry I keep saying this, but if anyone searches down the line I want this made plenty clear to them.

Mandic · « **Reply #39 on:** March 03, 2011, 11:00:48 AM »

Pictures:

Best shot I could get of seeing the stud between the 3/4 exhaust ports:

Light shining through the cooling fins and visible from the stud hole. So you can see that this hole does infact just go to air:

The leak was certainly worse on the right side of the motor. 3/4 chambers are starting to carbon up at just 25 miles on the clock:

Mandic · « **Reply #40 on:** March 03, 2011, 11:13:14 AM »

Sorry to keep posting posting posting in my own thread, but I want this information to be out there.

Just got off the phone with Ken at Cycle-X and explained the issues I've had. He is going to get me an F2 cylinder to take care of it and I'm sending him back the K ones that I have. Hate that this is extending my time off my bike(especially since I intend to use it for transport in this new city) but glad everything is being handled so great. The guys at Cycle-X have been great with me from the moment I called to price out the parts up until now. I cannot say enough about how I appreciate their help. I wish they had known this issue off hand, but then a lot of guys around here didn't either, so it is what it is.

Terry in Australia · « **Reply #41 on:** March 03, 2011, 03:23:13 PM »

Quote from: scondon on March 02, 2011, 04:40:34 PM

You will be able to find lots of discussion in his posts on this subject, including the one where Terry denies there is any problem haha.

Ha ha, ha ha, thanks mate, I was looking pretty smart until you brought that up, I think I'll go find a black tank to kick around my back yard for awhile...............

scondon · « **Reply #42 on:** March 03, 2011, 07:14:13 PM »

Mandic, there are o-rings that go at the base of the F2 block that are not part of any gasket set. They go around the base of the cylinder studs on the blocked off returns. Honda part# is 91301-410-000. Here's a link that shows the ring dimension in case they are no longer available(#6 in the diagram). If you have any trouble sourcing them, shoot me a pm. I believe I have 2 new in the bag.

http://www.cmsnl.com/honda-cb750f-750-super-sport-1978-usa_model7240/partslist/E++03.html

Quote from: Terry in Australia on March 03, 2011, 03:23:13 PM

Quote from: scondon on March 02, 2011, 04:40:34 PM
You will be able to find lots of discussion in his posts on this subject, including the one where Terry denies there is any problem haha.

Ha ha, ha ha, thanks mate, I was looking pretty smart until you brought that up, I think I'll go find a black tank to kick around my back yard for awhile...............

Sweet! I thought that tank might have floated out to sea by now. When your done kicking it you can run it through with the stubby ignition shaft that's about to land on yer doorstop

Terry in Australia · « **Reply #43 on:** March 03, 2011, 08:59:28 PM »

Quote from: scondon on March 03, 2011, 07:14:13 PM

Sweet! I thought that tank might have floated out to sea by now. When your done kicking it you can run it through with the stubby ignition shaft that's about to land on yer doorstop

Ha ha, I've forgiven you now Sean, and the tank is still high and dry, and intact. (Tim would kill me if I hurt it, he's very proud of his first "custom" tank) When I got home today there was a box with that weird little shaft thingy that you sent me, so all's well with the world, and I think we can both give ourselves a gratuitous pat on the head for correctly diagnosing Mandic's problem, you can't beat first hand experience! Cheers, Terry.

Mandic · « **Reply #44 on:** March 04, 2011, 09:07:38 AM »

Ken mentioned those o-rings, which I was unaware of. I will check the dimensions of the pile of o-rings I have when I get to the shop. I'm very tempted to run a bead of silicone around the studs up at the top of the cylinder to prevent water from getting down in there. I remember looking at my stock studs and those 4 being extra rusty and junky.

Ken also mentioned that after he looked at his old notes, what they used to do was press a sleeve into the base of the F2 head to form a slight seal to those studs. He forgot all about it until he checked his old notes. He just called me and informed me he is shipping my parts AND having the guys in the shop sleeve every F head they have around hahah

Terry in Australia · « **Reply #45 on:** March 04, 2011, 01:06:30 PM »

It looks to me like Ken is making it up as he goes along. For a guy who works with CB750 stuff every day, how can he have "forgotten" something as critical as this? How many of Kens customers would have had this problem? Sorry, but I smell BS.

Mandic · « **Reply #46 on:** March 04, 2011, 04:30:47 PM »

Eh I'd imagine more often than not customers bring him their bike or send in their cylinders. I ordered one of the cylinders they had pre-bored for an 836 because I was in a time crunch. The sleeve idea makes plenty of sense. There is space around the stud, you can sleeve it straight through the passage and seal off the stud from the outside world. A simple fix if you have the machinery to do it.

Terry in Australia · « **Reply #47 on:** March 04, 2011, 04:55:58 PM »

I'm not saying you can't mate, in fact I look forward to seeing how these sleeves work, I'll have to go take a look at my spare F2 head to see if it's really as easy as Ken suggests.

I just find it hard to believe that one minute Ken is insisting (against our advice) that there's no difference between the two cylinder blocks, and next minute he's saying that he knew all about the in-compatability of the F2 head to K cylinder block problem, but somehow forgot, and now he's referring to his old notes that he made last time he encountered the problem. He must have a terrible memory, eh...........

Mandic · « **Reply #48 on:** March 04, 2011, 05:35:05 PM »

I'm not getting the sleeves. He is doing the sleeving to all the heads he has in stock. So they can run K cylinders. He runs a business, I can see how you'd forget something you haven't dealt with in a while. It sucks for me, but he is doing right by me. He is sending me a freshly bored F2 cylinder to fix me up, new gaskets, and new rings.

Mandic · « **Reply #49 on:** March 10, 2011, 11:55:10 AM »

Received and prepped my new parts. Throwing on the new rings now, then time to drop on the cylinders. I was not able to come up with those O-rings and ordering them from Honda would have taken a week. Anyone have a thought on this? I intend run a thick bead of silicone around the cylinder studs on the unused oil returns to prevent liquid getting down in there. However I'm betting the o-rings are more about keeping oil from getting up and out. I have 4 o-rings that will fit but are not thick enough IMO. They only measure about 1.75mm thick. I intend to put them in there just don't expect a lot from them as far as sealing is concerned.

Is this going to be a major issue? I hate to do this and have to tear down all over again. May it make sense to squeeze a bit of RTV around the o-rings to create a slight seal? I am using a Cometic rubber coated steel base gasket with high tack on both sides of it to help seal a tiny bit.

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Author Topic: F2 head with K Cylinders, leaking oil all around the head. (Read 9981 times)