75 850 Head Gasket Oil Leak

About a year ago I disassembled and cleaned/painted my friends 75 850. While I was cleaning the engine I found a piece of woodstove insulation cord stuffed between the head and the Jug fins wrapped around the front and sides of the head/jugs. I remembered, vaguely, putting this in to prevent oil from getting on the pipes and other areas of the bike. It only had a few thousand miles on it at the time and I had torqued the head several times to try to stop this leak with no success. This was 1976 or 1977.
In any event, the bike is now weeping from the front of the head gasket again and drips on the hot pipes. I could replace the head gasket but there are no compression problems and the bike runs great. My inclination is to get another piece of woodstove insulation cord and stuff it between the fins like I did some 35 years ago. It did not stop the leak but it did eliminate the symptom......There is something to said for that.......Jerry

While the cord may hide, absorb, the unsightly oil from escaping onto the pipes, it creates another undesirable,
and that is that it directly prevents cooling air from hitting the base of those fins, and especially at a very hot area, right between the head and barrel.

Might be best to pull the head off, clean things up, and install a new head gasket.

Good point. The cord was less than 1/4 inch in diameter and frankly I'm supprised it was still in there. I have heard that on some Nortons oil seeps up the threads of the front head bolts and this can be addressed by removing the two front head bolts, putting thread sealer on and replacing them. My intent is to try this before pulling the head......Thanks.....Jerry

I had a very similar problem with my head gasket after rebuilding the motor. To solve it I re-knelled the gasket and installed it, hasten blown yet.

850bruno said:

Good point. The cord was less than 1/4 inch in diameter and frankly I'm supprised it was still in there. I have heard that on some Nortons oil seeps up the threads of the front head bolts and this can be addressed by removing the two front head bolts, putting thread sealer on and replacing them. My intent is to try this before pulling the head......Thanks.....Jerry

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Bruno order the gasket,, rip the head off,clean her up put her back together,,i have just recently replaced the head gasket on my 850 and trust me its not that big of a job,and you no everything is done properly and you will have peace of mind,,,and also no oil blowing all over your shiney clean motor...rich.

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Doing a head gasket really is not a hard job, it's just a awkward position you have to be in to remove it.
Here is a post I wrote on curing my head oil leak problems and to this day it hasn't leaked a drop.

\"I had all the leaks you have there and now my bike is completely drip free. This is what I did to cure it.
I had 2 pulled studs in the head up front so when I got them repaired I also surfaced the head.
I removed the 4 studs for the front rocker covers, cleaned out the threads in the head and locktited them back in.
I then took all the covers and resurfaced them by sanding them with emery cloth on a flat surface like a slab of granite going in a circular motion until it was completely flat.
You'll be able to see it.
I them removed the 2 studs in the barrels near the pushrod tunnels, cleaned out the threads with lacquer thinner.
I plugged the pushrod tunnels with paper towels as well as the stud holes and oil drain hole and used a NEW flat file and ran it flat across the surface of the barrels over the stud holes as the metal was raised around the studs holes. Just a couple of passes showed that they were raised enough to cause me concern and made me think that was one of the causes of the head leak.
After all that was done I used a shop vac to suck out the paper towels and filings.
I then loctited the 2 studs into the barrels making absolutely sure all threads were completely clean.
I took a new flame ring gasket and ever so slightly smeared hi-temp silicone on both sides of the gasket around the pushrod tunnel areas and the oil hole area.
I then assembled the head torqueing it in 3 stages.
I let it sit over night and retorqued it again before starting it up.
I let it run for 15 minutes, let it cool over night and torqued it again.
I rode it for about 50 miles nice and easy. Let it cool over night again. Torqued it again for the third time.
I did this retorque 5 times because the application of silicone to the head gasket adds some thickness to the gasket.
I also installed a reed breather I got from MikesXS http://www.mikesxs.net/products-40.html#products
It is also important to not over tighten the 2 long nuts in the front bottom of the head.

If you follow these instruction to the letter you to will be leak free.
Plus the spindle gasket and the rocker oil line copper washers should be replaced too.
That breather is real important. I've got pics on how I routed it."

Thanks Guido.......I am currently working on my 74 and although I don't what to do the head of the 75 until I get the engine back together on the 74 I'll follow your tips on the 74. The 74 never leaked anywhere (except the primary case) and had a copper head gasket so I have copper gaskets to reassemble it. I've already lapped the head and jugs but I can't figure out what to do to the copper gasket before I install it (I bought some NAPA spray sealant), there seem to be many different opinions with regard to copper/flamering, sealant/no sealant, etc that I'm tempted to just put it together with a copper gasket, no sealant, and see what happens........Jerry

I've used copper gaskets with no leaks, but you better be sure your surfaces are flat.

Dave
69S

i used Holymar in a spray can ,,,(blue),,,light coating each side of copper gasket after heating it ....

As I work in an industry where a torque wrench is extensively used (Schilling Robotics), what are you guys using in a way of a torque wrench to gain access to the three upside down head bolts, ie two in the front and one in the raer through the barrels?
I am due to do a rebuild on bike #2 and keen to know how you get the torque values right compared to the right way up others, just by guess work compared to the tightness with a box or ring spanner?
Am thinking of making and adaptor to fit my torque wrench for this
Regards Mike

If after all the prior suggestions fail, suspect crack in head as is a known issue on some 850's. Blow by of course with aggravate almost any head sealing initial success. Unless run with rather hi throttle and loads likely the cord didn't do much to stifle heat flow, but if locally hotter then the area distorts more than otherwise.

Torque wrench, we don't need no stinking torque wrench, just keep going till feels too tight or even more till the leaks stops or it don't.
As to T-wrenching, no defense to its best practice modern way to preach - when well applied with calibrated wrench and fastener conditions compensated for, but some of us just follow the Norton factory way is all to get away with it routinely. Set me straight please, seriously, that those that recommend T-wrench in all seriousness, that they pull out the T-wrench each and every time they re-torque or re-check the fasteners. Just takes once w/o using the T-wrench to blow all technical reasoning on Norton head fastening right out smoke free headers.

Having terrors to remove either over torqued &/or corroded in engine fasteners I now nip em up as tight as I dare with main worry to remove after their cooking - so always put anti-seeze to ease out later, which screws with torque level chart'ers of course.

hi Steve, not going to debate use of T wrench or not, but in all the engineering practices i was taught, t-wrench for flat surfaces for combustion engines and gaskets , using them was always a good policy plus I work with titanium bolts that are very small, we have some very heavy handed guys that i supervise and train , so encourage the use of them (t-wrench)for that.
Remember, there is quite a big difference in torque settings for bolts with or with out lubricated threads.
Still going to make an adapter for a T wrench for the three hard to get to bolts and then work out the valuse needed. Will fab up and post.
Regards Mike

Yep, I've no defense what so ever against T-wrench's in world wide long time real life practice in manufacturing with manual or robotic assemblers, watches to wind turbines. I remain of opinion that its not too much specified torque that lets Cdo head seals down but some other fault or this subject line would be rather rare than oh ugh not another one besides mine too again... Obviously not enough torque lets the pressure out and why we keep nipping up til can't nip no mo.

So fess up do you really only ever nip up each Cdo fastener fully as can by depending on a T-wrench? Only takes one sheep or goat date w/o protection to give a life time reputation of fact of the matter. So what heck if ya got away with it once...

Similar applies to the Amal, first reflex is over tightening but when really examined new out the box 32 mm flanges are distorted form the casting process and then can further bow with time heat and vibration over the stupid 0-ring interference.

In my Trixie Combat head leak it turned out to be too big a ring gap, but fooled me as stayed sealed for most a year good usage. Threads weep and heads crack so lack of T-wrench use is mostly a useless guilt trip to suffer till real faults dealt with. I only view the manual torque levels as starting points to work past till crush down and thermal settling stabilizes.

Even and equal torque being more important than amount of torque is why
you use a 'meter wrench.
Using ring type crows feet and doing the math allows one to
get on those bolts and nuts not readily accessible.
Will allow that Ive read things like "tighten with a six inch
wrench" or similar for those earlier days before a torque
wrench was in every mechanics toolbox.

Certainly agree there is plenty of bolts I've tightened all my life on subsea equipment , cars , motorcycles and god knows what else, just a stickler for the T wrench where necessary and where acess allows for my own peace of mind, that way it is only me who can beat myself up if i didn't use the T wrench and the head let go, all other discrepancies in the head/barrel fit up already covered!!!
Will crows foot or service spanner adapt, calculate extra torque by offset and try my best!!!
Have to go replace a leaking 1/4" hydraulic fitting at 3000PSI (probably from big strong technicians over tightening duh!!!!)
Regards Mike

When my head gasket leaks I just tighten the side that is leaking and then it stops leaking for a while, then it starts leaking on the other side and I tighten that side and it stops leaking for a while until it starts leaking on the other side again and then I tighten that side and then it stops leaking fr a while etc., etc. I've been doing this for about 30 years. Am I doing something wrong?

ah the peace of mind this brings to me... when read slowly, word my word...

just a stickler for the T wrench where necessary and where acess allows for my own peace of mind,

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When my head gasket leaks I just tighten the side that is leaking and then it stops leaking for a while, then it starts leaking on the other side and I tighten that side and it stops leaking for a while until it starts leaking on the other side again and then I tighten that side and then it stops leaking fr a while etc., etc. I've been doing this for about 30 years. Am I doing something wrong?

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I find the best method to be " tighten until it strips then back it off a quarter turn"

Snap On did a ring spanner with a 3/8 square drive at the other end for a Torque Wrench to go into, we used them in the RAF toolkits but I'll be buggered if I can find any on their website. This tool was Ideal for those upside down nuts pity I never "borrowed" one when I left the service.