Topic: CB750 K0 Leak after rebuild - ***Solved! I think***

[Simpson]

So I just got my top end put together.
Without starting the engine, just turning the engine over getting oil back into the system I have this oil leak.

The only possible scenario I can think of is a problem with the puck seals.

Does that sound right?

[fire113]

Hi Simpson,

...go and pull the towers, it is looking to me like the pucks under the cam towers.

[andy750]

Agreed on the pucks. Right spot for it. You need to pull the motor in any case to have a look. Did you use anything to seal the pucks in place?

[Simpson]

I used the permatex 2. I installed them with great precision and care. 

[CycleRanger]

Could be leaking from the valve cover down into 2 & 3 plug area.
I just had a leak in the same area because I (duh) installed the valve cover gasket upside down.

[Simpson]

Could be leaking from the valve cover down into 2 & 3 plug area.
I just had a leak in the same area because I (duh) installed the valve cover gasket upside down.

You know... before I go tearing this thing apart. Maybe I better be sure its not something simple like that top valve cover gasket.

Its a lot of oil, everything seemed flawless on installation but that top gasket. Didn't seem to fit correctly.
Now I just need to observe where this oil is coming from.

[CycleRanger]

Could be leaking from the valve cover down into 2 & 3 plug area.
I just had a leak in the same area because I (duh) installed the valve cover gasket upside down.

You know... before I go tearing this thing apart. Maybe I better be sure its not something simple like that top valve cover gasket.

Its a lot of oil, everything seemed flawless on installation but that top gasket. Didn't seem to fit correctly.
Now I just need to observe where this oil is coming from.

I could tell the valve cover was leaking, and it did leak a lot.
I couldn't tell why until I pulled the engine and the valve cover.

[Simpson]

So this is a picture of the valve cover gasket above the leak...
Yeahhhh.... this might be it? 

Good thing is I can change the gasket without taking the engine out.

[Magpie]

You can do that? Can you post pictures of it please and thanks. Cliff.

[yesteryear]

Simpson,

My k4 has got the same leak exact same area.Before I noticed this leak I re pulled the motor because it leaked at the side of the head.The reason for this some bozo had helicoiled the cam cap bolt hole and had drilled in to the cavity above the plug.Oil some how came down the thread and trickled by  the plug and spread across the fins.Sealing the thread cured that but I suspect on mine that is on one of the middle cam cap bolts there is another helicoil doing the same.Because of the first leak which is all I could see like a jerk I did not check all of them.So later I have to pull it yet again.Pour oil down the cam bolt holes and watch for the trickles.
hope this helps.
Yesteryear

[CycleRanger]

Good thing is I can change the gasket without taking the engine out.

Would that I had been so fortunate...

Anyway, yes, that's probably your leak.

[Simpson]

Old gasket out, waiting for NOS gasket coming in the mail.

Cliff,
If you take all the cover screws out (takes some wiggling) you can lift the cover and bend the gasket around the sides and install a new one.

[Simpson]

I saw this on eBay and the price made me laugh out loud.
107 dollars for used parts that are no good.
Ha!
http://item.mobileweb.ebay.com/viewitem?itemId=170808348956&index=0&nav=SEARCH&nid=32173821237

[Simpson]

Okay, now I'm really stumped!!!
Original leak fixed with new gasket, now I have a new one coming from this area!!!
%#@$%#%!!!

Anyone know where oil could be coming from inside the cylinder like this?
Everywhere else seems to be great, bone freak'n dry, except this stop.

 

[Simpson]

Bump!

[Simpson]

Okay, here are some better pics of where this oil trickles out.
Any ideas are greatly appreciated as to why this is happening.

Click pictures to view in detail. 

[Magpie]

I'll throw this out for consideration. The K1 engine has a bolt through the head to the cylinders there so a leak there may have been a common thing. I have 3 K0 engines and have had to use double washer on the studs to get the heads to seal onto the gaskets. After planing the heads a bit and perhaps the studs stretching (?) the nuts were bottoming on the studs and not torquing down. Maybe this is what's happening at the two studs in the leak area? The other thing that happened to me is that I used a thinner head gasket it turns out than stock and it wouldn't seal properly and leaked oil badly.
Cliff.

[Simpson]

Interesting idea cliff. Is there a bolt hole in the center of the cylinder that the oil can leak through? I cant figure out where there would be a hole for oil to leak through. Are the studs open in the center? Wish I had a spare cylinder to examine.

[Magpie]

i don't think there is a bolt hole through as the K1 head is a different casting at the front of the cylinders for the bolt to go through. The two studs at the centre front of the engine are visible through the fins. Shine a flashlight in there and you'll see them. If they are damp that may be the place it's weeping. Here's a picture of a K3 head with the "new" bolt just in front of the cam chain. You can just make out the stud nuts in front of the spark plugs, I wonder if they are the leak source? Cliff.

[MCRider]

Simpson,

My k4 has got the same leak exact same area.Before I noticed this leak I re pulled the motor because it leaked at the side of the head.The reason for this some bozo had helicoiled the cam cap bolt hole and had drilled in to the cavity above the plug.Oil some how came down the thread and trickled by  the plug and spread across the fins.Sealing the thread cured that but I suspect on mine that is on one of the middle cam cap bolts there is another helicoil doing the same.Because of the first leak which is all I could see like a jerk I did not check all of them.So later I have to pull it yet again.Pour oil down the cam bolt holes and watch for the trickles.
hope this helps.
Yesteryear

Yes, other than pucks, this is a viable place for an oil leak. The 4 studs across the front of the cam caps are often removed to clean the head. The holes they screw into are all drilled and tapped thru the head and open into each of the 4 spark plug cavities. Your PO did not do this.  What he probably did do was remove the studs, pulling out the threads on one or more of them. Then he helicoiled the hole. Making for an almost for sure leak as you describe. The oil wicks its way down the threads and drips onto the fins at about the 3rd fin level. Then it flows and drips of the front of the engine.

The OP may have this problem as well.

Moral: Do not disturb those 4 studs. If you do, replace them with studs and seal the threads. If the studs are gone and bolts are being used instead, seal the threads but be prepared for future leaks. Only the studs should be used in my experience.

By threading the stud in, with sealer and allowing it to set up, you'll have the best seal. Then a nut is used to hold the front of the cam bearing cap on, without disturbing the threads in the head.

The rear of the bearing caps do use bolts, but the holes are not open to the atmosphere so oil wicking down their threads has no where to go.

[Prospect]

Simpson,

My k4 has got the same leak exact same area.Before I noticed this leak I re pulled the motor because it leaked at the side of the head.The reason for this some bozo had helicoiled the cam cap bolt hole and had drilled in to the cavity above the plug.Oil some how came down the thread and trickled by  the plug and spread across the fins.Sealing the thread cured that but I suspect on mine that is on one of the middle cam cap bolts there is another helicoil doing the same.Because of the first leak which is all I could see like a jerk I did not check all of them.So later I have to pull it yet again.Pour oil down the cam bolt holes and watch for the trickles.
hope this helps.
Yesteryear

Yes, other than pucks, this is a viable place for an oil leak. The 4 studs across the front of the cam caps are often removed to clean the head. The holes they screw into are all drilled and tapped thru the head and open into each of the 4 spark plug cavities. Your PO did not do this.  What he probably did do was remove the studs, pulling out the threads on one or more of them. Then he helicoiled the hole. Making for an almost for sure leak as you describe. The oil wicks its way down the threads and drips onto the fins at about the 3rd fin level. Then it flows and drips of the front of the engine.

The OP may have this problem as well.

Moral: Do not disturb those 4 studs. If you do, replace them with studs and seal the threads. If the studs are gone and bolts are being used instead, seal the threads but be prepared for future leaks. Only the studs should be used in my experience.

By threading the stud in, with sealer and allowing it to set up, you'll have the best seal. Then a nut is used to hold the front of the cam bearing cap on, without disturbing the threads in the head.

The rear of the bearing caps do use bolts, but the holes are not open to the atmosphere so oil wicking down their threads has no where to go.

Is it possible to somehow seal the hole from outside around the spark plug cavities to see if that's the problem before pulling the engine?

[lucky]

I saw this on eBay and the price made me laugh out loud.
107 dollars for used parts that are no good.
Ha!
http://item.mobileweb.ebay.com/viewitem?itemId=170808348956&index=0&nav=SEARCH&nid=32173821237

One of the things that can happen on those early engines is that the metal locating
bushings can be too tall preventing the head from torqueing down all the way.
I found this out one time when I was pulling my hair out and measured the height of the locating bushing and found out one of them was taller than the other ones. I measured the depth of the hole and the height of the bushing. Anyway it is exotic but it can happen. A previous owner loses one then orders another one and it is incorrect.
The part supplier just thinks they are all the same and does not realize the exact height of it matters.-LUCKY


Did you know you can also buy USED float needles on EBAY for the cost of new ones plus postage??? Hurrrrrryyyy. LOl..lol..lol

[MCRider]

Great question! Never even occurered to me. You can see the bootom of the hole if you look at it closel, the plug cavity that is, from the direction of putting the plug in. #4 and #1 are easy. 2 and 3...

The hole opens up into the cavity at a point where the casting is at an angle so the bottom of the hole is angled. Clean it and dry it real good then lay some silicone up into the hole and let it harden.

Can't hurt anything.

When it happened to me, it was real easy to see the oil dripping out on 1 and 4. You could look in the fins with a flashlight and see 2 and 3. Yes at the end all 4 of mine were leaking and it was a god awful mess.

[MCRider]

Simpson: Are your cam bearings still with the original studs on the exhaust side?

[markb]

I'm with MCRider on this one.  I believe some of the other tapped holes for holding down the cam towers are drilled through too.  It doesn't look like it's the area you're having a problem with.  But I always put thread sealer on all the screws that aren't going into a blind hole.