Topic: MLS Gasket leak after top end build. Repair questions. Solved!!

[albertaboy]

My 2 cents: I ALWAYS oil the studs/nuts for anything that needs measured torque. If they are a little corroded, I wire brush the "male" threads and then use grease instead.

That's one of those things they taught us during the Apollo Program when I was in school. (Remember Moon Shots?) 

On these fancy gaskets that must crush a lot to make the seals, the correct torque is much more needed than on the old paper-fiber ones with goo smeared all across their faces. Those old-style ones sealed themselves shut after the 2nd time the engine reached temp. Those of you out there who worked on the old CL/CB72 and CA95 probably remember that: run it at least twice before giving it back to the customer, so it will be dry...

I have oiled this time. Thanks for the confirmation. There is often conflicting advice in any forum. Seems like one just cant read enough and more than one argument seems convincing....
Im about to head out, do a second torque, put her back together and hope it stops snowing so I can go for a ride.   

[iron_worker]

I would just like to point out that "always oiling threads when torquing" is probably not a hard and fast rule to live by. Some torque specs are specified dry, some lubed ... if they are specified lubed then they will usually go so far as to specify what type of lubricant because even that will make a difference to the final clamping force.

Hopefully the weather smartens up so you can tell us how it ended up. I'm waiting on a new rear tire and hoping to have another ride or two before winter if I can.

IW

[70CB750]

Some manual list lubed and unlubed torgue. Novak Adapters is one of them, but thats more of an exception than the rule.

[Jerry Rxman Griffin aka MuthaF'er]

Thanks a lot guys! Guess that's the weather thats heading here in the next few days. Please keep it! The mountains are beginning to get dusted as it is.

As far as oiled threads I have become accustomed to chasing the threads, both male and female, to insure a clean condition then apply only a light coating of oil to the male threads and wipe it off. I do not want to get any buildup that ends up in the bottom of the hole that prevents the proper torque. 

[albertaboy]

Haha... sorry Jerry. This is pretty early, even for this far north. Funny that it's the southern half of the province is getting the most.  What snow has fallen here had melted or melted as it touched down.  Presently raining as I write this but temps are predicted to go down just above freezing over night.  Friday may get warm enough for a ride.

I just came in from the garage after completing the reassembly. I warmed it up and no head gasket leak that I could see. I'll know for sure when I can get out and wind it up out on the street.

[70CB750]

As far as oiled threads I have become accustomed to chasing the threads, both male and female, to insure a clean condition then apply only a light coating of oil to the male threads and wipe it off. I do not want to get any buildup that ends up in the bottom of the hole that prevents the proper torque.

^^^ That! I thought thread chasing was only mine little mental disorder 

[iron_worker]

Good to hear man!

However,

Mine doesn't really leak until I get it fully warmed up and out on the highway. lol so let us know if you get out for a real ride. I'm really hoping it works out for you because I'm probably going to have to do the same thing to mine soon.

IW

[albertaboy]

Not good news.  I braved the cold temps and only went 6 miles around the neighborhood when I could see oil spatter. The leak is a bad as before.  MRieck suggested replacing the gasket but I wanted to give this one another try.  Back to the drawing board....

Although I need to find a solution, I have run out of time for this season.  Too many other neglected projects await before the real cold hits.

[iron_worker]

Dammit.

[HondaMan]

Not good news.  I braved the cold temps and only went 6 miles around the neighborhood when I could see oil spatter. The leak is a bad as before.  MRieck suggested replacing the gasket but I wanted to give this one another try.  Back to the drawing board....

Although I need to find a solution, I have run out of time for this season.  Too many other neglected projects await before the real cold hits.

Your [cold-snow] weather just made our news tonight!

[albertaboy]

Not good news.  I braved the cold temps and only went 6 miles around the neighborhood when I could see oil spatter. The leak is a bad as before.  MRieck suggested replacing the gasket but I wanted to give this one another try.  Back to the drawing board....

Although I need to find a solution, I have run out of time for this season.  Too many other neglected projects await before the real cold hits.

Your [cold-snow] weather just made our news tonight!

This is real early. Normally, I expect to see snow fall and stick about the 3rd week of October and sometimes as late as the first week of November.  It's to go below freezing tonight here in Edmonton but warm back up, next week, to day time highs of 21 Celsius ... about 70 F.   As far as weather predictions go-  I'll believe it when I see it.

[albertaboy]

I hope my wife uses her intuition and knows how badly I want this leak fixed.... cause I'm just 10 minutes away from removing the head.  The honey do list will have to wait another week.
I got up this afternoon and started disassembling. Tomorrow afternoon I will have another look inside.   I am suspecting my positioning dowels may be too tall. I never double checked there was enough clearance after grinding some (1-2 mm) off the top. Honestly, a stupid mistake if so  but I hope that is the problem so that I can get past it.  I'll post the results. Off to work right now.

[Jerry Rxman Griffin aka MuthaF'er]

Wouldn't that be a welcome find! Remember there are 2 different lengths used.

[BPellerine]

kind of ironic that there are so many leak problems on these bikes now I used to be told that my old brit bikes were lousy for this reason!mine never leaked with copper gaskets!but this could happen to me with my 836 motor so I better not upset the karma gods,hope you have success.bill

[PeWe]

CB750 very seldom dripping oil to the ground leaving a slippery spot as the UK bikes did. Old Triumphs, Norton, BSA always oil left.
When I bought the bike I heard that head gasket oil leak was std, sweating oil. No floods.

[BPellerine]

pewe my bikes left no trail ,but many did that were not cared for.bill

[albertaboy]

Turns out I ground my positioning dowels down to 17 mm.  I measured the recesses between the cylinder and head to be 20 mm.  That would be plenty of clearance to get a proper gasket squish.   What next is beyond me.  If the MLS is re usable, why isnt mine doing the job.  I've no problem springing for a new one... I just doubt that's the solution.

[Don R]

Drop the head on with no gasket and peek in there, pics?

[albertaboy]

Thanks Don R
Here is a pic with the head on, no gasket, no positioning dowels or o rings.  Bare.   The clearance is even all around. I might be able to slip a .0015 feeler gauge in one or two of the four corners but that's it.

Another bare shot.

When I put the positioning dowels in and the two small rear o rings, this is the gap with no pressure applied. The gap is strictly caused by the two rear o-ring. No other interference that I can see.

The other side

[Jerry Rxman Griffin aka MuthaF'er]

O-rings should compress!!??

[albertaboy]

O-rings should compress!!??

Agreed. They would compress.  Basically, it would seem to me that there is nothing preventing proper sealing of the surfaces. Why isn't this mls doing the job??  What is defying logic here? 

I have a fiber type gasket that came with the 65mm pistons.  To use it, I would have to put the dowels and packing o-rings back in but I am tempted to.  These gaskets must be sprayed with copper coat??

[Don R]

What we do now, Kimosabe?

[albertaboy]

What we do now, Kimosabe?

Lol.  Tonto, let me tell you what I did...  I sprayed the gasket I wrote about with copper coat,  put the dowels and o rings back in, placed the gasket, put the head on, ensured it seated all around and torqued it on to 21 lbs.   I'll be the first one in the history of the world to not be able to make a mls gasket work. What can I say. 

[BPellerine]

but if this one works who cares!on the serious side these cheap gaskets are good too many use them and the price is right!hope it works.bill

[HondaMan]

Here's something I have posted on several occasions: the O-rings that are coming in many gaskets kits (the orange ones for the 2 oil passages) are not thick enough. They are also too soft for 60 PSI oil systems (durometer about 45), but work OK on engines with roller-bearing crankshafts (20 PSI max), like KZ1000 or certain Suzy engines.

Here's how to check:
The compressed head gasket should now be approximately 1mm thick in the composite sections, since it was already squished. Lay your O-rings in the cylinder holes (oil feeds) where they will live, then lay the head gasket in place on the cylinders, too. Then measure how far the O-rings stick up above the head gasket. Chances are, they don't, or not by much. The O-rings I have received in the last 6 gasket kits are 2.4mm thick, and the recess in the cylinders, plus the head gasket, is about 2.3mm thick (or deep, depending on how you think of it...). This only leaves 0.1mm of a too-soft O-ring to try to hold back 60 PSI of hot oil: ain't gonna happen, in short.

To complicate this, some head gaskets also don't compress far enough. They must be 0.85mm to 1.05mm thick when set under spec'd torque. When released after that, they spring back about 0.1mm (thicker), so keep that number in mind for the following tests.

The durometer of the O-ring should first be at least 60 to hold back 50 PSI of oil at 6-10% compression (of its thickness). If the recess is, for example, 2.2mm deep and the O-ring is 2.4mm thick, then the compression is: (0.2/2.4*100%)=8.33%. This means IF the O-ring is 60 durometer and IF the hole is 2.2mm deep, then it would hold back about 45 PSI of hot oil pressure.

That means: it will leak...

So...I started buying thicker O-rings in harder durometers, and now have a large collection of those orange ones that belong to Kawasaki engines, and not to SOHC4 engines. They will work in the bottom of these oil passages if those recesses are not too deep, but other than that, they really don't belong in these engines.

I have the O-rings in 11x2.5mm thickness (Honda's spec) and also in 10.8x2.6mm thickness (so they will fit in the diameter OK) to solve this problem. Let me know if you need some? The postage is probably more than the O-rings, though.

Or, check through the O-rings you may have lying around: find one that is at LEAST 0.3mm thicker than the depth of the (recess+head gasket) and is black in color (not orange and soft) and stiff. This will help.